On why (some) humans have lost their body hair? Why are we the only hairless primate?

In case you have forgotten, humans have relatively hairless bodies when compared to our other great ape relatives, even to the 5,000 or so other mammalian species out there. This is curious phenomenon — we seem to defy the very classification of being a mammal.

Sure, there’s a lot of variation among human populations. Some of us are hairier than the others, while others of us aren’t. There are even known genetic ‘mutations’ that reverse our hairlessness into a ‘werewolf syndrome’ which is known in science as hypertrichosis. Fajardo Aceves Jesus ManuelFajardo Aceves Jesus Manuel of Mexico is a modern day example of someone with hypertrichosis. This condition is caused by a genetic defect that,

“causes the hair growth cycle in victims of this rare disease to run amok. The follicles from which the body hair grows are apparently incapable of switching from the growth phase to the dormant phase, which normally ends in the new hair falling out and the cycle begining again.”

Hypertrichosis is considered an atavism — or an evolutionary throwback. An atavism is a trait that reappears which had once disappeared generations ago. This happens mostly likely thru a backward mutation but it can also happen thru transposable elements within the genome, i.e., the ‘hairy gene’ was locked away in a region of the genome that was not expressed but then was shuffled and inserted into an expressable region. Other known atavisms occur thru this mechanism. Genes that coded for a previously existing phenotype are often preserved in DNA, even though the genes are not expressed in some or most of the organisms possessing them.

But hypertrichosis is a rare genetic disorder, actually it is very rare. Only about 50 cases of the condition have been documented since the Middle Ages. That indicates there has been a strong positive selection to keep us hairless. But why? Are there any evolutionary explainations as to why humans are hairless?

Well, there are three main stories explanations (?) for why humans lack fur. Scientific American has asked an expert, Mark Pagel, head of the evolutionary biology group at the University of Reading, and he summarizes these hypotheses for us. These hypotheses vary in evidence but they all revolve around the idea of a positive selective pressure to not be hairy. In other words, it may have been advantageous for the human lineage to have become less and less hairy during the six million years since we shared a common ancestor with our closest living relative, the chimpanzee.

The first hypothesis, named the ‘aquatic-ape hypothesis’ considers that way back in the day, like 8 million year ago an apelike ancestor of modern humans had,

“a semiaquatic lifestyle based on foraging for food in shallow waters. Fur is not an effective insulator in water, and so the theory asserts that we evolved to lose our fur, replacing it, as other aquatic mammals have, with relatively high levels of body fat. Imaginative as this explanation is—and helpful in providing us with an excuse for being overweight—paleontological evidence for an aquatic phase of human existence has proven elusive.

I was taught that our hairlessness initially came about from an adaptation that occurred as apes moved down from the jungles and into the hot savanna. Hairlessness helped control our body temperature when hominids made the transition to a new ecosystem.

“Our ape ancestors spent most of their time in cool forests, but a furry, upright hominid walking around in the sun would have overheated.”

This theory seemed to make a lot of sense, when I was taught this by my professors. However, it had one major flaw. The lack of fur,

“might have made it easier for us to lose heat during the day, [but] we also would have lost more heat at night, when we needed to retain it.”

A recent theory, one that I briefly introduced on Primatology.net back in March, considers that ancestors to modern humans were selected be hairless as a means,

“to reduce the prevalence of external parasites that routinely infest fur. A furry coat provides an attractive and safe haven for insects such as ticks, lice, biting flies and other “ectoparasites.” These creatures not only bring irritation and annoyance but carry viral, bacterial and protozoan-based diseases such as malaria, sleeping sickness, West Nile and Lyme disease, all of which can cause chronic medical problems and, in some cases, death. Humans, by virtue of being able to build fires, construct shelters and produce clothes, would have been able to lose their fur and thereby reduce the numbers of parasites they were carrying without suffering from the cold at night or in colder climates.

Human lice infections, which are confined to the hairy areas of our bodies, seem to support the parasite hypothesis. Naked mole rats, animals that can be described as resembling “overcooked sausages with buck teeth,” also seem to support the theory: They live underground in large colonies, in which parasites would be readily transmitted. But the combined warmth of their bodies and the confined underground space probably negate the problem of losing heat to cold air for these animals, allowing them also to become naked.

Once hairlessness had evolved this way, it may have become subject to sexual selection—being a feature in one sex that appealed to another. Smooth, clear skin may have become a signal of health, like a peacock’s tail, and could explain why women are naturally less hairy than men and why they put more effort into removing body hair. Despite exposing us to head lice, humans probably retained head hair for protection from the sun and to provide warmth when the air is cold. Pubic hair may have been retained for its role in enhancing pheromones or the airborne odors of sexual attraction.”

Will we ever know why hairlessness was selected for in our lineage?

No, just like we may never really know why bipedalism was selected for in our lineage.

But the problem with hairlessness versus bipedalism, is that hairlessness is one of those wild witch hunts that we embark on, one that relies on story telling and a whole lot of what-if’s. It is full of conjecture and not much scientific evidence. Regardless of its flaws, this question remains a very thought-provoking one to me, as someone interested in physical anthropology.

After writing this, I consider hairlessness could have been due to a founder-type effect. Since no supportable physiological significance can be drawn at this time, what if hairlessness became dominant a dominant allele because people who carried the hairless recessive mutant allele replaced people carrying the dominant hairy allele after a population bottleneck?

Again another what-if, however it is a plausible evolutionary possibility… But is it supportable?

No, not at this time… unless we figure out when this allele was really prevalent in our populations after a certain time and correlate its switch from recessive mutant to a dominant after some bottleneck inducing phenomenon, like an epidemic that targeted hairy people more. Until we sequence more paleoDNA from other hominids (mind you we can only extract nuclear DNA from Neanderthals, as of now) this hypothesis is also just as outlandish & unsupported as the aquatic ape one.

126 thoughts on “On why (some) humans have lost their body hair? Why are we the only hairless primate?

  1. All these theories are interesting, but my Gran who was born to British parents, with Dutch back to the 1500’s, and nothing else that stands out as being Asian, North American Indian or other , was completely hairless from her head down. Her eyebrows were thin and her complexion leathery but she was old. My father consequently has hardly any hair on his body except his head, whilst my brother and I have hardly any leg or arm hairs, fine head hair with some areas having noticeably less follicles. My children however appear to take after my husband and have what I would consider ‘normal hair growth’. Although one child is much less hairy than the other.

    So does this mean that there Must be some gene that is not working correctly, or perhaps my Gran was the milkmans and not my Great Grandads! Unfortunatley due to the death of her relatives, other than one surviving brother, I do not know if my Gran was unique in her family, or if one or both parents held this defective gene.

    This is NOT alopecoa, as in gradual hairloss such as Gail Porter,, this is genetic within my family, my very European family. Although there are some gaps within my family tree where the male relatives were Sea Captains who did travel to the Carribean, so it is possible to have picked up some different nationality relatives, and my Grans condition was obviously severe whereas mine is somewhat muted.

    I have found all your comments very interesting in trying to decipher why we are much more hairless than other Europeans. However, none of the answers really explain why different races have different traits, one can oly assume that evolution in the same mode as size or skin colour is to blame!

  2. It seems as if adaptations for hairlessness could have arisen as we began living in closer proximity and in larger groups during the Neolithic. There was an increase in infectious disease during this time, so it seems as if a loss of body hair could have somewhat somewhat offset an individual’s chance of being infected during this transitional period. Of course, this would mean that the loss of body hair was a relatively recent occurrence…

    1. Wrong. Does not explain why only white people are still hairy (even not so much as before). Native Americans, Africans, Asians, all lost the fur. Not white people. White people and their semi-white ancestors in Fertile Crescent were the first (with Egyptian) neolithic settled farmers. They lived in cities of about thousands of people quite soon after being farmers. On the other hand, even non-agricultural tribes in Australia etc. are hairless.

      1. Veronica, Australian aboriginal people, who call themselves Koori, do HAVE body hair. I had a friend, Melinda, and she was very pround of her strong, dark hair on the legs and arms. According to the new DNA study, the Koordi are the oldest human culture on earth, reaching back ab. 75 000 years.

        Since there are medical students around here, I’d like to know if the hairiness is bound with the amount of the skin pores ?

        1. Thank you very much Bridget for your post. Yes, they are not alone, of course, also some indoeuropean haplogroups have specifically thicker hair than others. By what I wrote I do not intend to propose the straight link between hairlessness and the colour of the skin. First farmers were not white people. Some mutations of melanin related genes in their area really happened, after they had continuous recourse to the agriculture. I do not think it was due to their new type of settlement, which was in fact specific for later periods. Some dramatic changes (leading to the pouring out of Agassiz lake etc.) took places in that times and it could affect more genetic changes alltogether. But it seems to be wrong assumption hairlessness could happen due to neolithic settlements, if nations who haven’t experienced neolithic settlements at all, all around the world, Africa included, are hairless too, and even more obviously ;) than many today’s white indoeuropeans who are successors of neolithic agricultural tradition. Also I think hairlessness is not due to diverse temperature in various areas. Melanin is more expected to be connected with the solar activity, with the distance from the poles and the distance some specific magnetic areas in the world as well, of course due to forests, waters (!), and many other influences, even it is not so clear too (look at the OCA2 mutation – in fact reduction of function – resulting to british blue eyes (not central african blue eyes) expecting to occur 10 000 years ago in Black sea area). But hairlessnes is due to some genetic shift, complex change preceding the others. The climate (so volcanos, waters etc. too) could function as the trigger as well of course, and probably did, but it is not the main and the single reason. The theory that people lost their hair because of the sun (and run) in tropical areas whereas in North people have been saved by fur before cold is ridiculous. No other animal does it. Also, the idea today’s white northerly population have lived in the same northern places always and for ages is bizarre and untrue. It would be similar as if people would like to explain the hairlessness in peruvian dogs as the result of climate change in Peru (here it is known today it is due to the mutation (interestingly – again lost of the part of the function) of one of FOX family genes which is responsible for development of embryonal states and it is human gene too – the dog was widespread (because considered as sacred) in Middle and South America long before Inca’s civilization and it is believed his ancestor taken to the breeding was from Asia). And also, the climate e. g. in Eem interglacial including Sun activity was different, not so much, but significantly, especially in some areas, to the possibilities of human evolution and spreading of the species. It is necessary to look for something more human-specific altogether and the suggestion of Judy Zifka below doesn’t look too sci-fi. I think Out of Africa theory impedes many truly interesting novelty suggestions, scholars tend to think within its limits, to squash their ideas in its boards because they have learn in school “it is true” and they’ve acquired the dogma. To be honest I doubt Koori population is “home” in their contemporary place as well, even it is likely their population is there much longer that some african populations on their places, but to my opinion, it beautifuly illustrates, among other examples, how the idea of losing hair due to the temperature is wrong. Or? Don’t you think? Or any other suggestions?

        2. Veronica, thanks for the long and intense explication…

          So it seems hairlessness, as a mutation, very soon became an important specie-specific, should I even say, a cultural choice. Individuals of the early Homo sapiens liked to choose the hairless partner rather than a hairy one, thus avoiding cross-breeding with different species like erectus, or later in Eurasia, with the Neanderthal).
          I think that’s the closest we can get.

        3. Personally, I don’ t agree with the “sexual choice” hypothesis at all, as well as I don’t think hairlessness is something specific for homo sapiens, even the second I regard as possible (not disproved yet). But I think homo neanderthalensis was hairless too, and even heidelbergensis and homo erectus, of course till some extent (similarly as Europeans or Arabians today, I think).

        4. How about a totally different angel …

          How much does our sex drive depent on sexual curiosity provided by clothing obscuring the genitals? What if the real adaptive value of hairlessness was that if forced us to clothe ourselves, and in so doing, generated an artifical sex drive to compensate for a weakening of the sexual instinct in the human line? We assume that humans still have a sex instinct, but do we??

        5. ;) I am not aware about many animals who are able of what you call “sex instinct” 24 hours a day during the whole year ;) and who use the sexual intercourse also for social hierarchy intentions (without intention of reproduction). This sex drive is similar to that of Bonobo, less to chimpanzees, so I don’t know but I would think its deviation from other animals :) (for quite a huge part of animals sex is in fact not pleasure at all and happens in allotted time) could occur much much earlier. the thing is that many people, regular homo sapiens, in most of regions of the world have been almost naked for the vast majority of their existence, long after we know they have had lost their hair. I really don’t think human species is the one who would need to be forced to sex. but I was also thinking about how the clothing could affect some physiological changes, because it is definitely for example electrostatic, it changes sweating etc. but nevertheless, to my opinion it seems more likely people started to wear clothing only after they were hairless, so they haven’t experienced these problems (otherwise they would be for example hairless only (or significantly more) in area when they wore clothing, etc.)

    2. I disagree. I think that it might have to do with stupid people marrying each others brothers and sisters and or first cousins or something stupid like that. We get all kinds of F+cked up mutations. This interbreeding caused all kinds of defects. I know that some europeans are not very hairy at all. You are not suppose to have a uni eye brow. They should be two. I guess someone married there sister along the line and this continued.

      The other thing is that these kinds of things are hidden for the most part. So that all these hairy people can hide it. If they had to walk around naked like many asians. The sexual selection process would rid us of hairy back ape people.

      Arabs spend all there days waxing until death.

      Though laser hair removal works. ha ha..

      1. It’s true we went thru a bottleneck, a period when it was a necessity to inbreed. We are all children of those 20-30 men and women.

  3. Right on Robert, yeah I think the Neolithic coulda been one of the times where hairlessness was selected for. I think you are onto something. The Neolithic transition was a critical shift, and could manifest founder-effect selection.

    Again, the problem still remains to find out when did was this mutation introduced into our genome… Until we find out, this and all the other theories are very speculative.

    Thanks for commenting!

  4. Kambiz, any comment on this?

    I’ve an OT question that relates to dinosaur feathers and hominid hair.

    When hominid researchers in the field find a skull, what is their priority? To pick and brush it off right? Since we know that feather imprints can be retained if the critter was covered in fine mud (rare but not unusual), shouldn’t skull diggers be looking at the inverse of the skull for hair imprints on the dried mudstone? Of course once the skull’s soft tissues decomposed, the surrounding silts or clays moving inside would destroy some of the features, but the dead hair protein would probably leave an imprint, possibly visible through MRI or micro or nano Xray analysis or something. I for one would like to know the precise hair/beard patterns, as I’m tired of paintings, drawings, models of ancient neandertals, erectoids and apiths with short haircuts, since sapiens have hair that grows a yard long when left uncut.

    But then again, some people think our ancestors were like chimpanzees on savannas, where long hair is useless. I do wish the bone & stone folks would check on hair, probably the only soft tissue recognizable after 20k years in the hardening mud.

  5. DDeden,

    Excellent question. I don’t know of any hominin fossils that told us something about the hair patterns and density.

    It could be that people aren’t careful while excavating the remains, but from my experiences, people really slow down and take it easy when they find a precious hominin fossil. I doubt that it has to be due to their priorities because there’s nothing more important than delicately removing a fossil, taking note of the context it’s coming from.

    That being said, a lot of why we don’t see fossils with evidence of hair patterns from hominins has to do with the sediment and chemistry the fossil was laid down in. Not every hominin fossil is formed because it settled in ‘soft muddy sediment.’ Fossils like famous archaeopteryx one, which show imprints of feathers, are rarities. Only a certain condition would yield such a result. Many fossils are formed in different sediments, with different chemicals, pumus, and even physical dynamics that affect the ability soft tissue is imprinted.

    The process to make a fossil takes thousands, if not hundreds of thousands of years, depending on the conditions. A lot can happen during that time. And it happens in different places too.

    Fossilization is the process where organic compounds in bone is replaced with inorganic minerals. Often, soft tissue, like hair and the skin it grows out of, is sloughed off and removed by natural phenomenon, scavengers, etc. Other times, hair just won’t last that long. You know how thin is, to have it degrade but still yield an imprint is rare. Even the most malleable sediment will fill in and warp.

    I guess the best paleoanthropologists can do, is to sample for trace elements, like degraded hair protein since that may last. I don’t think any sort of visualization technique, can, at this time, show us what you’re looking for.

    I hope that answers your question.


  6. Neotony. I curious about that as an explanation for many of the distinctive traits we see in our fellow primates. It seems to me lately that the hairlessness that we exhibit into our adulthood is somehow allied with the suite of other expressions of neotony, traits that figure prominently in who we were and who we were to become: big heads, thin skin, cartilage growth throughout life, and covered with fat. It’s not so much that we’re hairless but that our follicles never produce hair like a normal maturing animals in the population from which we diverged. Maybe hairlessness was a genetic inevitability as a result of the way our genes work in certain relationships with other genes. So maybe big brains mean that the potential to grow a heavy pelt is proportionately reduced. At some point the lack of a hair is overcome by the emergent concept of manufactured shelter and the enhanced security of communalism. Being able to tolerate ones fellow species members becomes a requisite for success in gaining access to mates. This kind of instinct for social bonding is not uncommon in young animals but later as adults the group becomes “us” and everything else is “out there”. But in another expression of neotony, our ancestors retained their flexible/elastic social instincts into their adult lives, reinforcing the cohesiveness that provides a degree of advantage over other animals with whom they share the habitat’s resources…and as we have continued to these times.

  7. Why are most native americans/Indians almost hairless, no arm or leg hair, yet they have a full head of hair? Is this typical? Is this a true feature of an indian or native american?

    1. Bobbie,
      I am mostly Indians actually over 3/4 and I have never had underarm hair. I have also heard that it is a characteristic of Native Americans.

    2. my great grandfather is full blood indian , i’m white lived mostly in arizona ,i have no hair on my arms or legs or under arm , i’m the only one in my family of 6 is this way.

  8. Bobbie Neu. East Asians generally have very little facial hair and Native Americans are presumed to have at least some East Asian ancestry. Could easily account for it. When I visited USA I met Pueblo Indians who had very sparse beards and moustaches, looked quite a bit like as Ho Chi Minh.

  9. The naked mole rat hairlessness as a method to reduce ectoparasites and suggested to parallel the reduction of hair in humans, is not supported. Lice are warm-body-temperature dependent, living between the skin and insulative fur; naked mole rats are virtually cold-blooded (very unlike the human metabolism). Their colonies are known to be very high in CO2 and low in O2, conditions not conducive to insects. Human ancestors were unlikely to have lived under those circumstances sustainably.

    Since most terrestrial mammals thrive encased in their fur coats both in tropical and arctic climes despite associated ectoparasites, something else must have caused human body hair reduction concurrent with scalp hair extension and retention of three species of lice.

  10. Here! I got another thesis!

    Perhaps, with the appearance of human consciousness and therefore a specific self image/identity, our women ancestors found less hairy men more sexy, because these more resembled a physical otherness from nonhuman animals. Other animals were seen as more primitive, somehow of lower status and hence those men which more resembled nonhuman animals because of strong hairyness were also attributed with that lower status. So women at one point, because of their human sense of identity started preferring less hairy men.

    Well at least that was the thing which first entered my mind 0,2 (0.2) seconds after reading the headline…

    1. Precicely my thoughts BUT why women selecting men. In primative times men selected their female partner sometimes without consent. I see a preference of less hairy females as being wifes to fight over. And as the generations progressed the outcome was substancial less hair. Pubic hair in a lot of tribal cultures was a signal of breeding age. so it remained in the both sexes
      The presence of more hair in mainly european s is largely climatic. Males having full thick beards and sometimes lots of body hair. obviously the females of european stock inherit more body hair because of this.

    2. Yeah, why not indeed?
      I have investicated the wolf / dog domestication and your argument could broaden my thought about the doggy history.
      Early dogs became the first pets with full of benefits . Getting involved so closely with another species was like what Galileo Galilei felt when he looked to the skies.
      That may have broaded the man’s mind and excelerated his conceptual evolution.

      So somewhere there women really began to think about themselves clearly different from the other creatures – and the more their partners differed from those, the better they looked.

  11. Obvious. Skin parasites prosper only in skin patches where there is hair. Selection favors skins that are unfriendly to parasites. Full stop.

  12. J: Whales have skin parasites yet lack hair.
    Orangutans have lots of long body hair yet lack lice, humans have very reduced hair yet have 3 species of lice.

    GVF: If hair reduction was caused by females preferring less hirsute males, why do males have more hair than females? And why during puberty do males get the hairiest, if that is the time of most sexual selection? It doesn’t add up. Hair reduction in most aquatic mammals does. Seems obvious to me that human ancestors spent some time day to day in seawater at the tropics, as many people do today.

  13. Yeah why are some better at being hairless than others? Asian/Native American/African. Could friction be part of it? Traveling through tall grass like in Africa. Native Americans are known for being able to quickly cover large ground through thick foliage. Tribes that live in thick jungles are always hairless. I’ve heard men who wear socks a lot sometimes lose hair from the sock line down….

  14. CJONES, I’ve been thinking about your comment for sometime now. I don’t mean to offend you by saying it is rather humorous to think about your hypothesis.

    To clarify to you and others, the real reason why ‘some are better’ at being hairless has to do with regional adaptations to temperature. Hair functions to regulate body heat. In colder areas, people are generally hairier. That’s not always the case, such as the Nepalese and Tibetan populations are relatively hairless. But in areas like the Caucuses,

    Hair is also hormonally controlled. As you may have noticed, hair growth increases along with puberty. While all populations undergo puberty, different levels of hormones affect the amount of hair growth.

    You may definitely be onto something, but I don’t think thickness of brush has a direct relation to hairiness. The reason why Africans are hairless is largely because most of Africa is hotter and losing hair may have been advantageous for thermoregulation. Asian populations, I dunno what’s going on with their hairlessness… but one of the reasons as why Native Americans are relatively hairless has to do with the fact that they were founded by Asian populations, so they were pre-dispositioned genetically with hairlessness.


    1. You get closer to the real reason for human losing their fur. It has to do probably with temperatures, but the reason why it is important to react to temperature is completely different from all the reasons that were brought up in the article AND the comments.
      I am writing an article that brings up a completly different reason for reacting to temperature with the loss of fur.

      It can be shown mathematically. All what I need is the approximate times (in the past) in which there were changes in our fur coverage and the size (weight, volume, …) of the brain as a function of time. I will appreciate it very much iif someone can point or provide such data.

    2. Ok, why i. e. arabian, persian and jewish populations are hairy? They have lived for thousands of years in the hot areas, with the very similar temperature as in Africa, South Asia, South America, and in many areas at least in few thousands of years also in the same humidity as in Africa.Why they don´t lose their hair after same thousands of years? It does not seem the temperature is the key. Also, I don´t think other mammals lose their fur in Africa ;) No offence :)

  15. Between 45ka and 30ka, the ancestors of the modern oriental people eg. Koreans, Tibetans, Vietnamese, and the Native Americans, and the Paleo-Siberians (excluding later mixtures) were geographically isolated at Lake Baikal, where they arrived during a warm inter-glacial period by following the flight path of migrating waterfowl from the African Rift and Paratethyan Black-Caspian basin.

    They lived at the north end of Lake Baikal along plentiful brackish hot springs at the edge of the Amur tectonic plate, and they maintained a habit of daily bathing and foraging (fish, molluscs, seaweed, reeds, lowland millet grains as well as medium size animals that came for water and salt) in the warm-cool waters there, continuously through the ice age.
    They did not have a strong stone tool culture, and probably used snares, traps, pits, weirs. Their huts were probably 1/2 dug into the ground, covered with skins and bark, insulated with reeds including tatami-like mats and furs.

    35ka, tectonic shifting opened the Angara river (the only outlet of Lake Baikal) which sent much of the warm water northward into the Yenesei river and the Arctic sea, but the springs still provided warm water locally.
    This caused a major diaspora.

    The tribe budded off into small expanding mobile bands venturing along connected river basins (Lena, Yana, Yenesei, Angara) and Arctic-Beringia coasts, having partially adapted culturally to colder water and climate with skin boats and improved big game hunting methods and switching from hot baths (retained in Japanese) to sweatlodge/sauna cleansing which depended on firewood fuel rather than hot springs. Because these bands were mobile, running out of fuel was not an issue, unlike sedentary people. Stone tools were made, but bone and ivory were as commonly used.

    At the same time in the west, people had adapted biologically by growing longer body hair, they lived along the Medit./Black/Caspian sea and marshes on fish, waterfowl and game thirsting for water and salt, including migratory herds, and quarried for stone in the Caucasus, Alps etc.

    After the last glacial maimum, warming induced some Baikal people to expand eastward along the Amur and up/down coasts to Korea/China/Japan (Yayoi), and others to migrate southward inland following flocks to Tibet, Burma and then south China.

    So we end up with Lapp, Manchu and Eskimo Inuit people who are relatively hairless biologically well adapted for warm seashores but culturally adapted for tundra plains and arctic coasts; and blonde hairy Norwegians and swarthy Georgians biologically adapted for sub-tropical forests and deltas but culturally adapted for plains and mountain valley herding and fjord fishing in open plank boats.

    A bit brief, but that’s the meat of the matter.

  16. That’s due to hydrodynamics as a selective agent, (barring conflicts with nursing infants both on land and in water, thus the lack of beard and chest hair in adult females). Better hydrodynamics = less macroturbulence = better oxygen and energy conservation. So, as you state in your post, “friction” reduction, especially in dense, viscous seawater during daily diving for seafood. Since children were not primary foragers, there was no strong selective pressure for better hydrodynamics until breeding age, so aside from scalp hair, children have only vellus hair and tend to be less ‘curvy’ compared to adults. Adult body form is more curved, partly due to childbirth requirements, so the crevices contain fluffy hair, what Darwin termed ‘coarse’ hair, while the scalp and body hair may be straight, wavy, curly or nappy).

    Coarse hair is nearly the same in all ethnic races, while the other body/mustache/scalp hair is unique to each group. Why? Because coarse hair is most effective in changing water flow from energy-costing macroturbulence to low friction microturbulence. Great apes lack an under-fur found in lesser apes and monkeys.

    Coarse hair at joints/crevices, subcutaneous fat at other locales, the head hair having unique requirements (infant grasping, nursing, previous hominoid hair position, lice being factors).

    IMO but not certain, this coarse hair in humans is the remainder of the primate under-fur, which was retained for better swimming and diving, but lost in the apes (which never dove).

  17. This all makes my think of a totaly different mater. Why does it looks like their was only a limmited amout of admixture between cro-magnon and neandertals. I think because neandertals evolved in a temperate to ice-age climate in the northern hemisphere seperate from other human groups since more than 1 million years (dmanisi ?)and thus had thick pelts (no need to ware clothing) making them sexually unattractive to hairless humans. This does not make them less human, only different.
    Since we know that neandertals lived as far east as Siberia, it is only waiting untill an ice-mummy neanderthal is found in the permafrost .

    1. question; did neanderthal have more bodyhair? Are europeans more hairy because of higher degree of mixture with neanderthals than asians? In the cold scandinavian winther, it is easier to keep warm with more body hair – like having furry underwear. But why do males have more body hair than women?

  18. Adriaan, that’s an interesting idea. Both polar bears and mammoths had fluffy fur pelts and abundant skin fat. I figure Neandertals had lots of skin fat, but I’m not sure about the pelts.

    My thoughts on neandertals: During the warmer periods they were probably naked, they probably swam a lot, they probably were quite hairy, maybe they had reddish -brown woolly body hair. Perhaps they group-ambushed various prey at waterside, then removed the whole pelt (say of a bear or moose) from the carcass, then smoked it, melting off any attached fat, killing the lice etc. then simply wearing that as a longsleeved outer garment during the cold months and adding some squirrel pelt mitts and grass-filled boots with twined cordgrass or tendons to keep everything tight and warm. Later simple sewing gave a better fit, cro-magnons may have brought sewing improvements to the area.

  19. I think a group of early hominids, who we mistook to be ‘barbarians’ were in true fact ‘barberians’, went around kidnapping hairy people and with really lousy scissors gave them bad haircuts so women ran away, preventing them from having babies. With hairless people having a strong sexual selection advantage, barberians began to lose their natural prey and their numbers diminished sharply – which in turn explains why it’s so hard today to find a good barber, especially for under $20.00.

  20. I’m way late in this discussion, but I’m curious about two things:

    1. Why most hairy men seem to have chest hair but not necessarily hairy backs. Great apes don’t have chest hair but they have hair on other parts of their torso. I know chest hair is related to levels of testosterone, even though that doesn’t guarantee a man will have chest hair, he probably won’t have a hairy chest without enough of it. So why chest hair and not back hair? Maybe so a baby can cling to his chest? Or maybe the sun on his back caused him to overheat and so losing it was an advantage.

    2. It seems like a lot of arguments for chest hair have to do with living in cold climates. But do chest hairs really make a man that much warmer? It doesn’t seem like it would.

  21. No cold climate mammals have body hair patterns like humans, but the walrus has a similar sparse distribution of hairs, not for warmth but for crevice filling, turbulence reduction and waterflow sensation during diving, the same reason humans retained it. The chest is bumpy, so hair fills in the low spots, the back is less bumpy except the tailbone-buttocks area which has some hair for better flow in water.

    The sirenians (manatee/dugong) have a similar pattern of sparse hair. Dolphins swim so fast that waterflow turbulence is not reduced by sparse hair, so they lost all their hair. Walruses, manatees, humans swim and dive slow, sparse hair reduces their drag. Women have less body hair because they spent less time diving and more time wading in the warm shallows with the kids and beachcombing.

  22. I have heard about high histamine ( Histadelics ) Have lower body hair .

    While people with low histamine ( Histapenics )
    Have increased body hair.

    Now histamine helps stimulate the immune system.
    Northern eurpopeans / Northern asians generally have far less body hair than their related southern populations .
    ( Italians vs Nordics ) (Asian indians vs Chinese)

    It is possible that the higher histamine may be helpful to ward off disease in the northern lands ( Although it seems most disease are far more southern in orgins )

    Also Histamine increases blood flow , circulation , lowers blood pressure.

    It is possible that the higher histamine levels could help northern populations withstand the cooler climates .

    ( Only problem ) I tend to find almost no data on histamine in ethnic groups . ( The few i have tend to have said african americans have higher histamine )
    Which i find strange . . Histamine lowers body hair ( Asians , Northern Europeans ) Check

    Histamine lowers blood pressure ( Asians , Northern europeans ) Check

    Histamine causes obsessive compulsive disorder .( In my opinions , Asians and Northern Europeans have much more obsessive compulsive tendencies than african / southern groups )

    But african americans have more asthma , allergies . ( So that is the true definition of the general traits of histamine )

    But there are also multiple histamine receptors and distributions through out the body!

    So perhaps asians , and whites have a alteration of histamine that influences a different end of the histamine traits .

    I also tend to find almost no data on histamine levels in humans vs apes or other animals .

    What i have found is .

    Vitamin C defiency causes Exessive Histamine . (Vitamin C is a anti-histamine )

    Also Humans are one of the few mammals which can not create our own vitamin c ..
    The mammals inclue ( Apes , Guniea pigs , Fruit eating bats , Humans )

    All eat alot more fruits containing alot more vitamin c than humans .

    So perhaps a Vitamin C defiency has caused ( Humans to lose their hair , Through Exessive Histamine .

    ( northern populations would have had far less intakes than vitamin c . ( Matches the less body hair in northern populations )
    Which also includes the ( Mayans vs the northern plains – eskimo indians )
    The mayans are more hairy .

    This seems to be a general world wide trait vs ( Northern Vs Southerns )

    The only exeption seems to be the ( Hairy ainu of northern japan )
    Which does not truely count!
    For the ainu are thought to be a tibetian / nepalese transplant into japan ( 6 thousand ? years ago ? or so)

    Best evidence of all is the sea mammals .

    Sea mammals lack hair . ( They also lack vitamin c!) = Less vitamin c = More histamine = Less body hair .

    Nothing in the sea really makes vitamin c . So all sea mammals have almost no existant vitamin c!

    It is thought that vitamin c is needed to protect life on the surface ( Not in the seas )

    Thus it is interesting that Sea Mammals + Humans are the only ones on earth to not have fur!

    Since humans can not make Vitamin C out of carbohydrates ( Like most animals can ) Since we do not eat tons of fruits each day like a monkey!

    It is thought we would need to obtain 1 gram of vitamin c a day to saturate our blood with vitamin c ( Like animals which create their own vitamin c make )

    This theory explains why Sea Mammals have no fur . Explains why humans lack it . It also explains why the northern populations which lack Fruits in their diets also have less body hair .

    The Testosteronee Theory is not true . ( African americans have higher testosterone than whites ) Yet generally have less body hair .

    With this said . It is in my personal opinion . That humans began to first lose their fur from a vitamin c defiency . Than later on this was reinforced by natural selection which rewired us to perfer less fur .

    Thus we became furless .

    1. Youre all speaking of walruses and other fish. Does hairlesness have to do with human hormones, or deseases [spelling] attributed to hairlessness in humans. Nat.Indians lived in very hot and very cold climates,some swam and some didn`t ,some walked in tall grasses and some didn`t.

  23. Sorry Matt, you’ve got so many errors I can’t correct them all. Seaweeds have vitamin C, all anthropoids lost the ability to produce vitamin C including foliavorous monkeys (including the swimming proboscis monkey of Borneo mangrove swamps), many sea mammals have abundant fur and/or vitamin C in their skin, etc.

    1. Why not? The idea that we were created this way is just as acceptable as some of the other ideas bring tossed around.

  24. KAMBIZ, I love your opinionated-ness.

    Devoter: Finding answers about life is part of being an open-minded person. Why would you choose to live ignorantly when an answer is out there? Besides “God wanted us to be this way” or “it was meant it to be, because of God”. Do you think God’s plan was to have his sons and daughters murder and be cruel people just to go to Hell? You think He created them just for that? If not, then how can you possibly believe we were just meant to be hairless because God wanted us that way?


    Food for thought..

    1. There are probably a multitude of evolutionary reasons why we grew to have less hair.

      I’d imagine that the primary reason was that we became able to insulate ourselves and thus its evolutionary importance was lost.

      Assume men are hairier due to spending longer periods working/hunting outdoors, than women so some residual benefit still remained

  25. Persistance hunting by the oldest tribe on the planet – San Khoisan people.

    This is done by hairless men walking and running for many miles tracking a prey animal in midday until it collapses with heat stroke. Humans have built in advantages – sweat glands for cooling and more efficient bipedal long distance locomotion.

  26. I’m afraid I’ll have to tip my hat in with DDeden here. There is some compelling evidence suggesting that many of our “peculiar” and unique traits are adaptations for living in a shoreline habitat. Many of our relatives take a bipedal stance when wading in shallow waters while crossing or foraging, and while hairlessness isn’t a hard rule where water is concerned, it certainly helps to eliminate drag (not to mention, just imagine trying to muck through the mud with all that hair!).
    If that’s not suggestive enough, consider that we humans require extensive amounts of EFAs in our diet (particular to note here – DHA) to support our massively oversized brains. EFAs are essential fatty acids that are called “essential” because the body cannot synthesize it and requires it. We can thank a diet of abundant EFAs for the resources needed to evolve the brain size that we have today. There are very few sources of EFAs. There are a few plant seed sources of some EFAs, such as flax, hemp, borage, etc, but these do not contain the needed DHA – the most abundant source of this oil is in seafood, such as fish and shellfish. The same can be said for Glucosamine and Chondroitin, which support our joints, and is also primarily found in seafood.
    Anyway, my two cent’s worth.

    1. You get closer to the real reason for human losing their fur. It has to do probably with temperatures, but the reason why it is important to react to temperature is completely different from all the reasons that were covered in the article AND the comments.
      I am writing an article that brings up a completly different theory/reason for reacting to temperature with the loss of fur.

      It can be shown mathematically. All what I need is the approximate times (in the past) in which there were changes in our fur coverage and the size (weight, volume, …) of the brain as a function of time. I will appreciate it very much iif someone can point or provide such data.

  27. Thank you Mark! There are books on this subject: Why We Run (by Bernd Heinrich, PhD animal physiologist and ultramarathoner) and the recent bestseller Born to Run by Christopher McDougall (another ultramarathoner).

    Basically, they’re right in that we don’t know why hominins INITIALLY went bipedal, but the genus Homo, according to the evidence, became the best long-distance hunter on the planet long before we invented anything more complex than a hand axe.

    Because our bipedality gives us an extremely efficient (if slow) running gait that a trained human can keep up for four hours, and because our relative hairlessness lets us dump waste heat easily, our ancestors hunted by running animals into heat stroke, then killing them by bonking them on the head with a rock. No fancy tools, just persistence.

    While I agree with the anthropologists that hairlessness may have started for some other reason, the massive selective advantage it gave our ancestors (being able to eat meat if you can jog for four hours) was a powerful selective pressure. Couple hairlessness with our form of bipedality, and we become highly effective omnivores.

    The aquatic ape hypothesis is seductive, but it suffers from testability. Your average dog can swim faster and hold it’s breath longer than your average human, yet no one hypothesizes that dogs evolved from recent aquatic ancestors.

    1. But weren’t the dudes the hunters? Shouldn’t, by that theory, women have more hairiness, not less, then men? So far, I have to think it has to do with being in water.

      1. Men and women share the same genes, so a selected-for trait will show up in both genders (unless it’s specifically selected for in one gender).

        Women are less hairy than men because body hair growth is largely dependent on testosterone levels, which are much higher in men.

        1. Are you saying that (eg. most East Asian) men with very little body hair have (much) lower testosterone than (eg. caucasian) women?

  28. but why do we still have hair on our heads? and what about people who go bald? does that mean anything significant

    1. We have hair on our heads because it protected out scalps from the sun in the savannah.

      I don’t know the exact reason for baldness, but my guess would be that it’s a byproduct from the way some peoples’ bodies manage scalp hair. It might’ve stuck around because it generally appears later in life, past the main reproductive stage in our ancestor’s lives. Traits that show up later in life tend to have no effect on an organism’s probability of successfully passing on its genetic information, and thus can stick around for no apparent reason. An example of this is Huntington’s disease.

  29. Is it even possible to know the full evolutionary when and why of how we got to be the way we are?
    I think that risky lives and small populations of a smart critter like a proto-human could see clever but maladapted individuals surviving to become, as much by chance as fitness, the foundation mums and dads of homo sapiens. ie we are like we are by dumb luck because once upon a time all the fittest men didn’t return from a hunt and the ugly sod with no fur, ordered to stay behind and do menial work – the one who hung animal skins around himself just to keep from freezing – goes on to father some clever furless kids who hung animal skins around themselves too.
    Maybe not literally but the how and why could rest on pivotal events in our ancestral history like that.
    I’m not convinced that sexual selection would be all that selective amongst very small groups of proto humans either, at least until well past the events that brought on the the demise of the furred. Like I do with choosing to surmise a male as the founder of the line – just to be contrary – I’m surmising the habit of collecting furs and fill their shelters meant when a nasty cold period hit the region it wasn’t the naturally furred ones, but the furless who did best.

  30. Sorry, after consideration, I think sexual selection within very small groups of proto-humans would indeed have to be an important factor, however I doubt that a fur-less mutant would be the most attractive even if, by cleverness, skills and parental social standing they could still be desirable as a mate. I suspect that, initially at least such an appearance would be considered more reminiscent of babies than of juveniles on the verge of sexual maturity; I am presuming that juveniles would have been furry like adults prior to changes that made us fur-less.

    It might take time and the right situation for furlessness to reveal itself to have advantages with respect to shedding excess heat – and be dependent on other adaptations like more and more watery perspiration that would not have happened at the same time. Advantage from reduced parasite load would at least be fairly immediate – my own hypothesis that finer, sparser hair allows greater tactile sensitivity to very small impulses than thick fur would make for better awareness of parasite presence as well as allowing them to be more visible for removal.

  31. I can’t read all those comments, but I think that the reason for fur loss might happened because of the human brains evolving and starting to make clothes when they were cold. And because of the body fat.
    But for bold people.. That just might be a genetic disorder.
    I’m not really an expert, and I’m not old enough to be one, but that’s just an idea.

  32. Hi there

    V.interesting comments, great to see the theories and love of knowledge here…

    I have a question which I don’t think has been covered above, apologies if so… My 6 year old just asked why I have a hairy chest and he doesn’t. I tried with some “don’t worry son you’ll get one too” support but that doesn’t seem to be his interest ;)

    He asked if it’s because mums and kids stay at home where it’s warm whilst dads go out in the cold. Sounds basic but not a bad theory for a young mind ;) Or if it’s just colder when you’re taller… (our previous question was why there is snow on a mountain even though it’s closer to the sun, so I think he’s seeing if any of that can be applied here… (that one was difficult to answer!)

    Any thoughts on this specific difference of why dad has a hairy chest and not the little ‘un?

    Cheers all, and keep questioning :)


      1. Hi Kambiz,

        Thanks for the reply, but this is not quite the question I wanted answering ;)

        For me, testosterone would explain the “how”, but not the “why”…

        Body: Dude, you need hair when you get to 13, so I’m going to give you it using some different levels of this n that
        Me: No worries sounds good, but why?
        Body: Dunno, I just work here innit

        I mean, monkeys have hair when they are babies right?

        Big disclaimer: I failed Biology ;)

        1. Monkeys have both an under-fur layer and outer “guard hair” fur layer, this is the basic ancestral trait for all mammals (fur + milk nursing = mammal).

          Great Apes have lost the inner fur layer due to tree-top nesting in tropical rainforests, where thermal insulation was less significant, but biting insects weren’t (so some apes have thick fur on their more-exposed back but less on their chests (they sleep curled in a ball in the bowl-nest)).

          Humans, on the other hand, split from the apes 5,000,000 years ago, with the chromosome #2 translocation, which in my opinion induced altered behavior, by producing a hominin species which spent more time at waterside foraging & bathing and sleeping in inverted bowl-nests on the ground, aka geodesic dome-like huts, waterproof and insect-proof. Thus no selection for fur coat.


  33. Just a thought, but what about fire? When humans “discovered fire”, I’m sure having hand and arm hair didn’t feel too good when singed.

  34. The most recent view is the naked love theory. Here’s the theory’s abstract:

    All primates except human beings have thick coats of body hair. This suggests the primate ancestors of human beings likewise had such body hair and that, for some evolutionary reason, lost their body hair. Various theories have been put forward but none is fully adequate. This article presents the “naked love theory.” This theory locates the origin of human hairlessness in the ancestral mother—infant relationship. In this view, hairlessness is ultimately the adaptive consequence of bipedalism. Because of bipedalism, ancestral infants lost their prehensile feet and thus lost the ability to grasp the mother’s fur with their feet, as do other primate infants. Early bipedal mothers were thus under pressure to carry the infant. Therefore infants survived only if mothers had a strong desire to hold them. Because of the pleasure of skin-to-skin contact, the desire to hold the infant would have been stronger in mothers possessing a hairless mutation that enabled them to give birth to hairless infants. Survival of these infants would have then been greater than that of hair-covered infants. The hairlessness that began to appear in this context of maternal selection was then reinforced by sexual selection in the male—female sexual relationship. This is because a hairless sexual partner would have enabled the hairless individual to recreate the pleasure of skin-to-skin contact in the mother—infant relationship. This theory then helps to explain the evolutionary origins of romantic love.

  35. I wrote quite a bit about how ancestral daily semi-aquatic foraging may have produced the mostly hairless condition in humans. There is one additional factor involved, more significant in general hair loss than aquatic foraging. Guess it!

  36. The aquatic theory…. you see that aquatic mammals have more fat and, having humans more underskin fat than other mammals, you think we had an aquatic time in our evolution.
    I think we swap cause and effect: water itself doesn’t cause fat growth. The heat transmission in water, the heat you lose, cause you to grow underskin fat.
    The lowering of body temperature causes, through selection, a favour for underskin fat.
    Now we have hominins without fur; hominins that suffer the cold temperature during the night. They use fire but who camped knows that fire is not always so effective.
    So…what is the second choice of a mammal to protect is body against cold temperature after he has lost is fur? underskin fat, also in air environment. It is not water, it is temperature loss that causes underskin fat, don’t you think so?
    Do human groups living in artic regions since thousands of years have a higher average level of underkin fat in comparison with tropical humans? This could be a good indication.

  37. But there is one issue that none of the theories in the above article addresses, namely the wide range of body hair volume that exists among humans today, even among males with similar androgen levels.
    Unlike the hair on a human head or even the face, body hair behaves exactly like fur. It grows to a certain length and stops, and follicles shed hair and are replaced at regular intervals. I would surmise that people who today who still have this body “fur”, carry an active form of the genes from our ancestors prior when human body hair was lost (very roughly around 1.2 million years ago according to “Before the Dawn” by Nicholas Wade. I am sure regional heritage is a factor. I am of Italian decent and have “fur” on nearly every inch of my body. I would say this trait is mostly found among Mediterranean men, but I also have a Russian friend almost as hairy except his fur is light in color.

  38. It seems that human activity has a direct impact on body modifications ; thus high altitude living would produce a population with larger lungs and larger chests , a trait which is passed on through the generations . A relatively hairless population may have evolved from living next to thermal spa areas with high levels of caustic minerals present .

  39. I know this thread hasn’t been very active lately, but I had to put in my two cents about the evolution of hair, because I think I’ve finally got it figured out. Hair is ultimately an extension of our nervous system, and each hair has one or more nerves attached to it. There is a huge allocation of nervous system resources dedicated to hair.

    Hair is therefore intimately connected with the nervous system and to the brain. Understand that while hair is an appendage of the skin, its ultimate purpose is as an agent of the nervous system whose function is to gather sensory information. It is a way of extending our awareness beyond the confines of our body. The same is true for animals. Hair is what tells their brains what is going on around them. It also helps keep them warm, makes them pretty, and a bunch of other stuff. But that is just icing on the cake. The primary purpose of hair is as a sensory organ.

    So why did evolution favor humans losing their body hair? As humans were evolving and getting bigger brains, the increased resources that were needed to develop more brain neurons had to come from somewhere. The resources came from hair. It was the only part of the body that had extensive resources to draw from.

    Every step of evolutionary advancement that our brain made has been accompanied by a loss of body hair. The more we dedicate our neurological resources to the brain, the less we have to dedicate to body hair. The smarter we get, the less body hair we have.

    Some types of body hair have not gone away, and it is because they provide some sort of survival advantage. Pubic hair, for example, was not only retained throughout evolution, it actually increased. While the nervous system was taking energy away from body hair and feeding it to the brain, it was adding new resources to pubic hair. You think monkeys have hairy genitals like we do? Nope.

    The reason? Once we started walking upright our potential mates couldn’t just come walking up to us and sniff our crotch, like a monkey can do. We had to find a way to trap our pheromone odor in a way that would make it available to those around us while we stood upright. Since pheromones are so important in sexual selection, evolution favored the retention of hair in our smelly zones. Consequently, humans have developed a hair pattern that is quite the opposite of the other mammals — we have relatively hairless bodies and hairy genitals.

    Hair has many purposes, but its role as an agent of the nervous system has been largely overlooked. And its inverse relationship to intelligence is something that is quite thought provoking. Among other mammals, there are just a few that don’t have body hair. We assume that whales and dolphins don’t have hair because they are aquatic. But what if they don’t have hair because they are so smart? Maybe their nervous system has been directing energy away from hair and towards the brain just like ours?

    Among land mammals, there are just a few that are considered to be nearly hairless. Elephants, hippos, and pigs are examples. Guess what? They are also all considered to be very intelligent.

    And have you ever heard a description of an extraterrestrial visitor, who surely must be very smart to find his way to Earth, having hair? Nope. ETs are always hairless. That’s because having lots of hair and having lots of brains are kind of incompatible. From an evolutionary perspective, it makes a lot more sense to dedicate neurological energy to expanding the brain instead of using it for hair.

    1. Completely rubbish – the hypothesis of hair reduction reducing sensory nerve load and therefore supplying extra impetus to the growth of the brain. Absolute garbage!

      1. I heartily disagree, Chris, and the intensity of your denial leads me to believe that I may be on the right track. I suppose my feeble attempts at humor by including the ET reference made you think I wasn’t serious, but I am. I work with hair every day and these observations are based on actual experience with hair, something very few researchers have. I am a former scientific researcher who jumped ship and now does body waxing — the removal of hair. I have seen how the nervous system responds to hair, and it is clear to me that hair is an agent of the nervous system. The connection between hair growth and brain growth is well documented. There is something to explore here, and vociferous denials such as yours frequently herald the first shift of new thought. In fact, I thank you for phrasing it in such a concise way for me. Hair reduction reduces sensory nerve load and therefore supplies extra impetus to the growth of the brain.

        1. Judy,

          Humans have as many hair follicles as chimpanzees – by some accounts, even more – but we appear denuded only because our hair is shorter and much finer. We therefore have as many sensory neurons devoted to hair as we ever did, and your hypothesis that there has been a reduction in sensory nerve load that made its associated neurons availabe for brain expansion duirng human evolution, is plainly wrong.

        2. Chris, the assumption you make is that because we have as many follicles as chimps we therefore dedicate as many sensory neurons to hair as they do. This is an incorrect assumption. The neural “load” that hair requires is not a function of the number of follicles but rather a function of the sensory nature of the hair itself. Hair is, first and foremost, a sensory organ. The thicker and darker the hair is, the greater the sensory load it carries.

          Part of this is due to the “antennae” shape of hair and another part is due to melanin within the hair. Melanin is a paramagnetic substance and this means that hair (and skin) displays a mild magnetic attraction to external electromagnetic fields. Operators of MRI are well aware of this paramagnetic quality. This magnetic attraction is how our brain uses hair to gather information about the electromagnetic fields around us. All mammals have this ability to use hair to collect information and then respond to it.

          When hair is thick and dark, such as on a chimp, there is strong conductivity between the external environment and the brain through the hair. The longer length and more abundant melanin within the chimp’s hair creates a better antenna to collect data. Their brain is therefore presented with a higher neural load of sensory data. Shorter, thinner and paler hair such as found on humans will transmit less sensory information and therefore place a lighter neural load on the brain.

          The data collected by hair delivers (albeit subconsciously) important information about the external environment. As a mammal, humans were at one time more hairy like the chimps, and we used our hair in the same manner. But something was different about humans. We started paying less attention to the world around us and more attention to ourselves. As we focused on ourselves we got more intelligent, but we had less resources to focus on the world around us. Hairless humans became somewhat out of touch with the environment, and some would say we started wrecking it.

          This loss of connection with the environment around us would have been an evolutionary failure if it were not for the fact that applying our nervous system resources to our brain (ie., self-centeredness) allowed us to figure out ways to overcome all the disadvantages of losing hair. When we got cold we figured out how to make shelters and clothing. All sorts of intelligent solutions have been developed by brains that were not spending so much of their neural resources on data collected by hair. We may have lost touch with the environment, but we got smarter and figured out new ways around it. And in the process we kept losing our hair.

          So, even though we humans have the same number of follicles as a chimp, the structure of the hair growing from those follicles transmits very different signal loads. This idea that hair is intimately tied to brain function is quite novel, I will agree, but I think it stands up well to scrutiny. The implications of it are quite far-reaching and explains many unanswered questions.

          Don’t forget that evolution is not over! We are still in the midst of it. .

        3. Hi Judy,

          It is well known that brain cells are devoted to collecting sensory data – indeed that’s why every cell in an organism has a dedicated nerve cell in the brain. That is also why it’s not the size of the brain that is important for intelligence, but rather, the ration of brain to body mass. That is a well known scientific fact. Nothing new here.

          When you make statements such as those below, you need to be aware that these are hypotheses that need to be proved:

          The neural “load” that hair requires is not a function of the number of follicles but rather a function of the sensory nature of the hair itself.The thicker and darker the hair is, the greater the sensory load it carries.

          Hypothesis only become creidible and interesting when there’s supporting data.

        4. Just to belabor the point (because I think it is important to discuss this), I am not alone in making this connection between the brain’s evolution and our body hair. A review of a paper written by Nina Jablonski entitled “The Naked Truth: Why Humans Have No Fur,” describes part of her thesis as follows:

          “In the final section, Jablonski blatantly states that “The loss of most of our body hair and the gain of the ability to dissipate excess body heat through eccrine sweating helped to make possible the dramatic enlargement of our most temperature-sensitive organ, the brain.” After this, she then goes into detail and conveys to the reader that between the years of the australopithecines and H. ergaster, the human brain doubled in size. Also, the brain doubled in size again from the H. ergaster to the modern human brain. With this knowledge, it is clear that the loss of fur in humans are what shaped our brain to what it is today. While some may say that being furless causes social repercussions, which make having no fur an inferior attribute in humans compared to other species, Jablonski argues that humans’ loss of fur is what has made us socially advanced due to the fact that we are so much more intelligent, and the only way this phenomena was able to occur was by our simple loss of fur. In conclusion, it is clear that Jablonski was correct in her statement: “naked skin did not just cool us down- it made us human.” The loss of human fur was not merely a big step in our evolution, it is what paved the road for us to become the advanced species we are now.”


          The entire article is quite interesting because it discusses a variety of reasons why humans have lost their hair. I don’t think she’s got it 100% right, but she seems to be on better track than most in understanding what is going on.

        5. To my opinion, there is a problem you want to find one single straight connection. There is no linear link between the size of the brain and the amount of receptors and development of PNS. Similarly, there is no linear link between the amount of melanin and high or low function of the receptor itself. Bigger brain doesn’t mean more neurons or less or more PNS receptors (i.e. hairs in that case), also, people with black hair or darker skin are not people gifted by stronger senses or predisposed to magnetic sensibility, thicker and darker hair does not mean more sensoric data, it is not so sipmle. Also, there is no one type of hair follicle. The only straightforward link here is the better the ear, the better the sense of touch, which was observed in many experiments and which seems to be logical. Otherwise, your point is very well targeted, to my opinion. I think it is possible that the mutation of KRTHAP1 could proceed as a part of the process of changes in sensoric system, which were repressed by the brain evolution. More interesting, it can be also vice versa, or both as a side effect or adaptation. But to what? In autistic individuals, sensoric perception is more profound, at the extent of some neuronal connection in specific parts of the brain. Interestingly enough, these missing connections causes the impairment of the specific type of social coexistence in a troop, which we find today as typical (it doesn’t need to be too old). It does not mean either they are less intelligent, neither they have bigger brains (even the temporary macrocephaly is not unknown case among autistic children in some years of development). In fact, among autistic individuals, copious hairs (thought on head), fair skin and light eyes are absolutely not the exception, often on the contrary, it is common. They suffer from the sensory overload. Children who are not autistic in their homelands in the developing countries become autistic after moving in the north countries (known especially for Somali communities, which call autism “swedish” or “american” disease, according to their new country, and others). It is not known why. Vitamin D/cholesterol etc. way was examined, but with no substantial result. It speaks against your desirable direction, but it also seems to me you hit the bull’s eye in some way. The interesting fact about KRTHAP1 is that its mutation should, according to the theory, proceed at about 250 000 years ago. In this time humans were spread out all around Eurasia.

        6. You’re making a lot of claims that have little scientific backing. This “neural load” you’re talking about just seems to be excess sensory information from hair follicles? And as our brains got larger we focused inwardly instead of on the environment and lost these sensory inputs? There’s no evidence (at least that I know of) suggesting anything like that, or even any connection between PNS activity and brain size.

          Ancient humans lived in Northeast Africa, where, at the time, there were dramatic climate changes happening every one or two hundred years. There would be periods of monsoons and wet, tropical conditions, and then not even two or three generations later, huge drought periods; and this cycle repeated for a long time. These constantly changing pressures selected for the best problem solvers (highest intelligence) in our already upright ancestors. This is why we have large brains.

          Body hair loss is connected to our bipedalism; we began walking upright as we left the forests. Our upright posture is four times more energy efficient walking on land than chimpanzees’. Humans are also amazing distance runners; we have the capacity to run hundreds of miles at a time, and it’s the reason our race spread all over the planet. Along with our dietary switch to meat, this suggests ancient humans performed persistence hunting, which is hunting by stalking a prey until it tires out or overheats. Overheats being important here. Losing our hair, developing sweat glands, and the ability to breath through our mouths while running (which both improves air flow and removes extra heat) combated this excess heat, gained by our environment, and running such enormous distances. Yes, sexual selection might have had an impact, but the main reason is what you’d expect in something with less “fur” – to maintain less body heat.

  40. I suspect that the relative lack of hair will be found innately linked with some other genetic factor with true adaptive value. Especially since we can offer so many contradictory reasons why lack of hair or fur might have been adaptive for humans as above. That suggests it is not relevant to evolutionary success.That different groups of humans vary in the amount of hair that is typical and even between young/old and male/female supports this idea.

    1. Just a thought: Since we now know that there were Flores Hobbbit, Red Deer Cave people, Denesovian, and whatever else that has not been found yet walking the earth alongside us in the last 30K years how about a contributing factor being simple differentiation? If we are visually different and select for the same it is easier to know friend from foe.

      1. JDN, yes, and I have already suggested that same in my comment above.
        All the animals do that, they are very strict and careful with their outlook, and the different ones are easily let outside.

        That’s called sexual choice and still works and shapes our evolution.

        1. It’s an old phenomenon known by the biologists for decades and called sexual choice. It’s so primitive that it may rather be called pre-social behavior . Birds do it much, too – when females choose the “man” in the “best suit” – ie. the most distinctive species-specific outlook.
          That’s why birds have so colourful feathers.

      2. It is really strange idea. Animals do not select their appearance with regard to other species, they select it for their own purpose, within boundaries of the own species, in all cases, even sexual, it doesn’t cross the border of the species, unless it has some predators’s value (mimicry etc.), and then it applies to the species which is far (not relative) from their own. There is no visible similarity to deduce such a conclusion. If they do, they do not shift their appearance negatively (because it is not apt to look like something), but only positively (to be apt). Which is actually the direction in evolution works, not vice versa (it would be huge loss of energy if it would be on the other way round). Name a single case when some animal make up the colour of its skin, amount and distribution of fur, size of the head or I don’t know the colour of the sclerotic because of the other animals just for some social reasons, that’s nonsense, They are real more useful and needed reason to be followed for them. If it would be like you sketched out, it would be a rare exception, which is not contra evidence – in fact, there are many exception in human species, so why not this :) But it is not possible to derive such an idea by the state common in other species – it doesn’t exist there.

        1. Veronica, sorry but that’s the worst non-sense U wrote above… Actually, what are U trying to express – besides that U seem to claim that animals can’t choose the best, the most fittest and beautiful partner (if availble) for them ?

          Also, U ask me to

          >>>>>>>> Name a single case when some animal make up the colour of its skin, amount and distribution of fur, size of the head or I don’t know the colour of the sclerotic because of the other animals just for some social reasons, that’s nonsense, They are real more useful and needed reason >>>>>>>>>>

          Well, I give U the very recent one – dog. According to mtDNA, the wolf / dog lineage broke ab. 100 000. The oldest dog fossils found are ab. 32 000 old. They show somehow dogs evolved neoteny – with longer down-jaw, flobby ears, bigger eyes, etc. That may have happened rather in an isolated, united population than due the individual choices – but in the early human history, the thing might been the same when our ape ancestors landed on savannas, leaving the other apes in the forests.

          Birds are the classical example to utilize the sexual choice – or in English I now see it’s rather called “sexual selection” (by C. Darwin) . The most classist is the peacock – why it has the wonderful tail ? It’s because the females compete to get the male, who has the most stereotypical features.

          That IS the main bases of the human evolution too. U just won’t find any evidence to deny it – unless U are a creatonist (sigh) .

          This is a good link to glance some points in the sexual choice / selection (skip the maths) :

          Click to access pnas00657-0459.pdf

        2. Bridget, it is nonsense to argue here more, your comment is totally out of place, you don’t answer to what I wrote at all, you are really locked somewhere in your own thoughts. I do not claim “animals can’t choose the best, the most fittest and beautiful partner” at all, I’ve claimed it never on any of my previous comments. I emphasized the difference between the choice within the species and outside it. I suggest to end this debate to prevent the forum before nonsensical replays. As for the dog, I think I’ve already stressed sufficiently already, why that creature is not the good example to depicture and enquire after the standard evolutionary mechanisms. I think I’ve said enough. Have a nice day.

        3. Veronica, U say

          >>>>>>>>Animals do not select their appearance with regard to other species, they select it for their own purpose, within boundaries of the own species >>>>>>>>>

          But that serves the “own purpose” idea (as U call it) – the more U specify into the features of your own type, the more distinctive you become. Sooner or later, a new sub-species is born . Of course, it demands, in the very beginning, (geographical or other) isolation from the main population . But when the lineage is broken, like U say, you can’t go back anymore if the sexual signals (mainly outlook) the two related specie perform have evolved too far from each other.

      3. I have another possible clue to follow: NEOTENY. It is true our brain (and even some other parts of the body) are juvenile, we mature much longer than other species. I think it is not necessary to specify here on anthropology forum all related featured. It would be possible the loss of the hair is simple one of the sign of human neoteny :)

        1. But, in fact I am not convinced about such a view, because to my opinion, there is quite evident difference in dispersal and thickness of hair among apes and monkeys which could not be explained by this approach and which can be related to the human loss of hair. It is just another fragment, playing a big role in other parts evolution of human, but not necessarily here, in evolution of loss of hair. Even it could be useful for some next thoughts somehow.

        2. Veronica, it’s a bit hard to follow Ur thoughts… First U say it’s the females who choose hairless men ( = sexual choice), then in next comment U deny it totally. Then U say it’s the neoteny, and again, as next step U say U are not convinced after all. So Veronica, tell me U are a troll and make my day ?

          Anyway, good U picked up neoteny, since this blog has been telling us all non-sense about the main issue especially in the comment’s side.
          Neoteny was presented by the biologist Louis Bolk in 1936. After him Julian Huxley had animal breeding programs on the same theme. He found that neoteny affects in other animals too (besides the humans).

          The genetic base of neoteny lies in the mutated genes controlling fast evolution.

          But what was the reason these mutated genes became general in our species ? I see there’s no other explonation than the sexual choice. And why’s that ? Because, our species is not so virginal at all as many seem to think, lol .

        3. I’v never said females choose hairless men, I don’t agree with that theory at all. On the contrary, I expressed my disagreement here already before twice, you can check it above. You have to confuse me with someone else.

        4. Regarding neoteny, dogs are selectively hybridized by other species (human), they have been domesticated for over ten thousands year. It is not a wild “animal”. Of course, they have signs of neoteny, domesticated species usually have, that’s the whole point of neoteny. Few other, non domesticated living organisms have netoeny too, but they are really very, very rare, it is not “typical” at all. Humans show all classical signs of such a “domestication”, that’ s an old song. In humans, and here I have to say more precisely in homo sapiens or homo sapiens sapiens, it was fixed not by a single genetic mutation, but by a longer period of various complementary genetic assessments as a response for some conditions. Some portion of our neotenic modification is due to changes we have undergone only in several thousands years ago, with the overlap no more than 20 thousands years ago after we became farmers, which many of today completely hairless hunters-gatherers haven’t passed at all. That’s why it doesn’t correlate quite well to me with loosing of hair. But they could be more stages of our “domestication” (adaptation to the new possibilities, weather, environment, amount of CO2 and really many many others) in the past, which is very likely and on of them could be related with hairlessness, so that’s why we can not dismiss this theory at all. The good source for some (speculative) points about human neoteny from the older scholars is Stephen J. Gould. Of course, your proclaimed sexual choice, which you present be the main reason of the change of the appearance, is the evolutionary trigger as well, I do not think someone doubt it. But it is always the CONSEQUENCE of other, primary changes as environment, temperature, food, lack of some common sources (it was one of the biggest movers in our past), which all requires different lifestyles. It is wrong to use our today’s environment as the specimen for surmises about the past in all its particulars, as it seems at least to me you do (not only with dogs), but if you already look at it to compare, its outlines are visible here as well – every sexual choice is the result of lifestyle which is the response for changed conditions. I do not see nothing intricate on it, I am sorry.

        5. The neoteny in early dogs (less than 32 000 yrs old) can be actually tell only by the lenght by their muzzle (and floppy ears, possibly) – the other features I presented, are of course newer.

          Since I try to write economically, that might have given U the idea I mean the Pekingese is 30 000 old breed.
          So, that is why U had to say :

          >>>>>>>>It is wrong to use our today’s environment as the specimen for surmises about the past in all its particulars, as it seems at least to me you do (not only with dogs) >>>>>>>>>>>

          I really never wouldn’t do that stupidity. I’m an studied, amateur biologist, especially into the Canis – species for years now.

          U must be familiar with the Belyaev – fur farm fox (Vulpes vulpes) breeding program ?
          It showed that domestication was “fixed” in four generations and that it also produced those neotenial features like floppy ears, but also “un-natural” colour outfits like spots.

          It seems to finally proof that domestication and neoteny are linkes genetically together, also with us, as U note too.

          Simply said, the human hairlessness is the result of that – you don’t need the water ape theory or the enviroment change .

  41. And that all serves the fact that when the two belong to the same species, ie. share the same behaviour, living style, communication, energy – could we even call it here “culture” – the progeny has the best chances to be plenty, healthy and so perhaps survive well .

  42. Monkeys have both an under-fur layer and outer “guard hair” fur layer, this is the basic ancestral trait for all mammals (fur + milk nursing = mammal).

    Great Apes have lost the inner fur layer due to tree-top bowl-nesting in tropical rainforests, where thermal insulation was less significant, but biting insects weren’t (so some apes have thick fur on their more-exposed back but less on their chests (they sleep curled in a ball in the bowl-nest)).

    Humans, on the other hand, split from the apes 5,000,000 years ago, with the chromosome #2 translocation, which in my opinion induced altered behavior, by producing a hominin species which spent more time at waterside dive-foraging & bathing (thus slightly selecting for hydrodynamic skin surface but retaining hair at the limb joints (reduced turbulence) and on the scalp (infant gripping hair as all other primates infants do) and more importantly sleeping in inverted bowl-nests (dome huts) on the ground, which were waterproof and insect-proof, thus no more selection for fur coat at night (sleeping in enclosure) nor during daytime (mild temperature at waterside). All apes weave basket-like nests, only humans weave portable carry-baskets and ground-enclosing dome huts.


    1. Dear DDeden, the theory U are pointing at is the one of Alister Hardy, a British marine biologist who presented it in the 60s.
      Tho’ great critics have been targeted in the “water ape hypotecy”, it has not been totally knocked down.

      U seem to repeat all Hardy’s famous proofs for the theory. But, another more recent proof is too rarely mentioned. If and when our oldest ancestors lived by the sea, they had the most wonderful source to feed themselves – the seafood. Now we know how very important it is for our brain development and mental capacity to get omega-3 oils. The fish and shellfish are its best sources .

      When those hominids were not delphins after all (-lol-), so I think it would more precise to rename the theory “beach ape hypotecy”, what d’U think?

      1. To Bridget: obviously you did not read my whole comment, you focused only on the small part which mentioned waterside foraging (which was actually just a subset of ground foraging), as opposed to the typical forest canopy fruit foraging common in ancestral apes. Early human ancestors were forest ground dwellers, but they were generalized foragers (underground roots, underwater shellfish, shrub fruits, floating water lilies, small group predation, etc.).

        Human ancestors 5.2ma due to the Chromosome 2 mutation switched from the canopy to the ground, inverting their woven bowl nests into woven dome huts, and by 3ma were making sharp stone axes to cut down small fruit trees, fruit & water-filled liana vines, papyrus & water lily rhyzomes and large herbs like banana plants, making sharp spears, etc. Hardy did not mention any of this, because he thought they left the forest for the seaside, just as others thought they’d left the forest for the savanna, both are now known to be incorrect, rather, early human ancestors left the forest canopy for the forest ground.

        Fur loss was primarily due to hut dwelling at night (no flying biting bugs inside), while hair tuft placement was affected by both ground living (scent distribution more important among ground dwellers (eg. dogs) than among water or canopy dwellers) and waterside foraging as noted in my above comment.

        Forest ground hut dwelling due to Chr.2 mutation was the critical element in natural selection producing the unique hominoid that became human IMO.


        1. In Your 15 lines long comment included 5 lines about the so-called water ape theory, so ab. 1/3 part . The rest was about the change in the nesting culture of the hominids. You seem be concentrated on it much (where’s Your source) – I have not red any article about that. It’s hard to proof how they lived, since there’s no material evidence left. The first possible fire places found are 400 000 old, but that’s too late of course.

          Australopithecus fossils found in South Africa, aged 2,5 – 1,8 million yrs, seem to have lost there hair to great part, since they lived in caves and used tools suitable for skin cutting. Many scientists agree from that the Homo erectus evolved and so Autralopithecus should be seen as our true ancestors – clearly different from apes, but still resembling also them to many aspects.

          What happened BEFORE Australopithecus, is more uncertain, but do U feel too that the CH2 – integration / mutation happened before that ?

          Scientist agree the chromosome 2 is the “brain chromo” or “intelligence chromo”. I feel that moving to the sea shores was the outer chemical facilitator that made the fusion of the two separate telomeres of the CH 2 – chromosome possible – or at least to spread in the population. The omega 3 (marine animal olils) is so important to the brains that if a mother doesn’t get it enough, her brains would shrink during the pregnancy.

  43. The Chr 2 mutation “producing a hominin species which spent more time at waterside dive-foraging & bathing… and more importantly sleeping in inverted bowl-nests (dome huts) on the ground”. That was my message. The Chr2 mutation had no connection to aquatic lifestyle, but through time humans on the ground did spend more time immersed, in the same way that deer and pigs spend more time immersed than canopy birds/monkeys/apes. Were there some ‘aquatic effects’ in human evolution? Yes, but those did not genetically distinguish humans from apes, who’d already permanently split 5.2ma, while living in tropical forests, as humans, chimps and gorillas still do today. Flax grows far from sea shores, was used in early weaving, and contains much omega 3 oils.


  44. Hey Bridgit naturally grazing animals have fats with the same Omega 3 fatty acid concentrations as white fleshed fish. If you are American you probably don’t know that cattle, pigs actually prefer pastures to feedlot corn ( which doesn’t deliver Omega 3). Early hominins didn’t need aquatic species to get their dose of Omega 3. Basically they had a go at eating everything they could lay their hands on – and, other than for shellfish or some crustacea, most fish hunting required highly adapted tools and coordination skills that took some time for hominins to develop. So brain development pre-dated salmon in the diet.Nothing wrong with the open grasslands,Serengetti/Olduvai Gorge evidence

    1. I just wish the blogist would blog out all nonsense creationist bs. This is a blog kept by a medical student, and so it’s a scinece blog. At least I believed so. It will be very blurry if that nonsense pours in.

    2. Deborah, I’, European. How about iodine, then which is also very important to the brain development ? It’s plenty is the fish and shells.

      Omega-3 consists three different types – ALA, DHA, EPA. ALA is plenty in wild grass (seeds) the animals eat and they can turn ALA into active omega-3. It’s true the naturally fed cattle has better omega 3 – values in the meat, because they can eat what they feel / like is the best for them. There’s a Swedish study on this (2004) in the net.

      But I’m not alone with the thought that living near shores, eating much sea food speeded up the homo brain / culture devolopment. Seafood is the most economical to get both DHA and EPA.

      You are wrong with the fishing, great amounts of fish land on the shores annually, still, in Labrador Canada for instance. You can very easily just pick up tens of hundreds of kilos of fish on the shore.
      In the ancient times, when the fish were so much plenty than today, this phenomenon must have been richer we can imagine. Also, catching a fish with bare hands from an ancient sea that was so rich with fish wasn’t just a task for our ancestors as you think. Even clumsy brown bears can do that.

      1. Yes, aquatic & esp.marine foods are richest in brain-specific nutrients (S.Cunnane 2005 Survival of the fattest). Nevertheless, archaic Homo were probably too heavy & slow to have caught fish frequently with bare hands.
        – Archaic Homo (erectus, neandertals & relatives) had typical features of littoral animals (pachyostosis, external nose, larger brain, flatter skull, flatter femora, worldwide dispersal, found amid shells, crossing to islands etc.), their skeleton was too heavy & brittle to have run a lot, they dived regularly for sessile foods such as shells & probably seaweeds, but didn’t fish much AFAWCS.
        – Some populations (esp.later, eg, neandertals) apparently ventured inland seasonally along rivers, where they ate cattails & caught ungulates in shallow water or mud, butchered drowned herbivores etc.
        – Frequent fishing seems to have appeared with sapiens (loss of pachyostosis, more gracile skeleton, longer tibiae, loss of platycephaly, narrower pelvis, latero-laterally instead of dorso-ventrally flattened femora etc.), they waded with spears/harpoons & later used nets & boats to catch fish & waterfowl.
        Google “econiche Homo” or “Vaneechoutte Tobias”.

        1. 1/ it is (widely) believed h. erectus was excellent long distance runner. it is well known his bones were similar to homo sapiens (distribution of strength, with the exception of legs). it is proved he lived beyond coasts and his diet consisted of portion of marine sea animals (fish, crocodiles, turtles etc.) it is quite likely he was (perhaps even the first) hairless hominid. also, at least to my knowledge, the majority of promoters of aquatic ape theory think about its time as about the time of homo erectus (or even before). we should mention here he lived mostly in Asia (Arabia, India, SouthEast Asia, it is even quite likely he inhabited Australia, actually he lived in Java, which doesn’t seem to be something else than an island ;) ) he and homo heidelbergensis were the origin homo for the huge part of modern humans across Europe and Asia, who were represented by various human species here, including perhaps homo sapiens too (which of course doesn’ say they ALL are related). and it seems homo sapiens experienced the tiniest changes of many habits, in comparison to his erectus ancestor (if he really was his ancestor and they had not evolved separately).

          2/ there is no “loss” of pachyostosis, “loss” of platycephaly etc. towards homo sapiens, we can not speak about any “loss” when h. neandertalensis was not his ancestor. they evolved separately.

          I am not dogged fan of aquatic ape theory just because I find personally other stages of the evolution more interesting, even I don’t want to refuse its blatancy, but no one have had ever introduced any serious contradiction proof, whereas there is riche evidence speaking for it.

        2. A few other comments to Veronica, who said: “there is no “loss” of pachyostosis, “loss” of platycephaly etc. towards homo sapiens, we can not speak about any “loss” when h. neandertalensis was not his ancestor.”
          Veronica, this is irrelevant: all archaic Homo fossils had platycephaly & pachyostosis, of course, although to different degrees (He>Hn>Hs). The losses of pachyostosis & of platycephaly in sapiens (+ longer tibiae, narrower ilia, more vertical thoracic processus spinosi, more basi-cranial flexion, loss of platymeria, loss of supra-orbital torus etc.) reflect IMO the transition from littoral animal diving parttime for sessile aquatic foods, to a riverine animal parttime wading for aquatic & waterside foods, presumably using spears/harpoons & later boats & nets to fish. Whereas the principal foods of erectus-like people initially were predom.hard-shelled invertebrates & aquatic plants (supplemented by drowned carcasses, turtle, bird eggs etc.), later Homo (eg, neandertals) ventured inland along rivers seasonally (salmon??) but kept collecting littoral foods (eg, at Gibraltar, see Stringer cs PNAS), and finally sapiens didn’t dive any more but waded & walked bipedally for waterside foods.
          Endurance-running (the nowadays popular fantasy) is even more recent, and is only seen in a few people (only adult men) in a few remote inland populations in E.Africa & Australia, but the majority of humans still live at coasts & rivers.
          Google: econiche Homo. Best –marc

  45. Hi all. There seem to be some misunderstandings here about the so-called aquatic ape theory. I read: “The first hypothesis, named the ‘aquatic-ape hypothesis’ considers that way back in the day, like 8 million year ago an apelike ancestor of modern humans had…” This is completely wrong (based on outdated info?), of course. The littoral theory of Pleistocene Homo (a better term than “aquatic ape”) is about Pleistocene Homo populations trekking to different continents & even islands (Flores >18 km oversea >800 ka, long before any evidence of boats) along coasts & from there inland along rivers. This littoral theory has nothing to do with Australopithecus, Ardipithecus, Orrorin, Sahelanthropus or other “apes”, but it’s about Homo much later during the Ice Ages, adapting to a littoral lifestyle: wading, beach-combing & diving for shellfish & possibly sea-weeds (& probably also collecting waterside foods, eg, drowned ungulates, stranded whales, coconuts, turtles, birds & eggs etc.). Homo fossils or tools 1.8 Ma are found from Mojokerto in Java to Dmanisi in Georgia to Aïn-Hanech in Algeria to East Turkana in the Rift (1.8 Ma, stingrays also appeared in Lake Turkana). Homo didn’t get there running over open plains as some paleo-anthroplogists still seem to think (google econiche Homo), but simply along the coasts & rivers. The sleketons of H.erectus & other archaic Homo were much too heavy & brittle to run (google pachyosteosclerosis). All tetrapods with pachyosteosclerotic skeletons are slow & shallow divers for sessile foods. No reason why erectus (or at least their immediate ancestors) must have been an exception. This would also explain the appearance of an external nose, of their flattened skull, their flattened femora, their large thorax & very wide pelvis (flaring ilia) etc., as well as our huge brain (thanks to the brain-specific nutrients in aquatic foods: iodine, DHA etc.), our body build with head-spine-legs in 1 line (hydrodynamics), our thick subcutaneous fat tissues & our fur loss. If some relatives of ours ever lived in savannahs, it must have been along the rivers & lakes there. For recent info on the littoral theory, google Vaneechoutte Tobias, or contact me.

  46. Veronica said:
    – “It is (widely) believed h. erectus was excellent long distance runner.”
    Yes: “believed” is the correct word: erectus’ bones were too heavy & brittle, they were everything but distance runners: google “econiche Homo”.
    – “it is well known his bones were similar to homo sapiens (distribution of strength, with the exception of legs).”
    This is nonsense, eg, erectus’ parietal bones were almost 3 times thicker than those of gorillas, and the skeleton was much denser. These features (google “pachyosteosclerosis”) are typically & exclusively seen in littoral animals. No wonder we find erectus from Flores to the Cape to Pakefield in England.
    Veronica’s rest is even more fantasy. Please, Veronica, inform a bit.

    1. You claim a schoolboy mistake speaking about the “loss” in different branches only because it is (and actually in the concrete case it is even not unreservedly) in consequent time. It doesn’t seem too credible regarding your knowledge, I am sorry. I would recommend a bit of self-reflection before starting to give advice to other people.

      It is true the distribution and strength of homo erectus skeleton have the biggest similarity with the skeleton of homo sapiens (and homo heidelbergensis where some related features differ), in comparison with neanderthals who got the different evolutionary line (especially on the west), based on archeological finds. But it is necessary to keep in mind there are notable differences in erectus remnants all around the world (of course!;, i.e. turkana vs. others, etc.). Dmanisi is the likely origin place of h. e., neanderthals and other northern hominids (including northern erectus) evolved under different climate conditions, whereas sapiens evolved on the previous southern erectus regions where even erectus has specific marks and where the climate changes had not affected so dramatically his lifestyle as far norther. Perhaps also from erectus, perhaps they evolved here separately side by side, no proof yet. Erectus height is the closest to sapiens. Mind they were not so separated species as we often see them today, almost without continuity. It all doesn’t deal, of course, with the information about the difference in thickness of bones and robustness of skeleton, which is higher in erectus. But it was even much more robust in neanderthal skeletons. So the difference is lesser in h.e vs. h. s.. Propositional logic. Is it clear already?

      It is actually hard to find what’s your aim, claiming pachyostosis is a contradictory proof against aquatic ape hypothesis – it is an absolute nonsense, on the contrary, it is used as its support (it is a solid part of one of existing aquatic ape theories which are six or seven placing its time to different era and other variations). I don’t think in 2012, many people interested in the topic would cherish the picture of fully underwater homo animal never mind in which era of the evolution which it seems you try to oppose. You replied to Bridget who haven’t suggested anything like this. Actually she was probably right about fishing, h. erectus did hunting turtles, crocodiles (Kenya, Java etc.), at least it is highly unlikely he left fishes of shores untouched on ground, and the next step seems obvious. Humans, apes etc. always ate what was available in their regions. Surprisingly. It is only good to add again homo erectus differed at that time all around the world, even we speak about him as about the species with one single chracteristics. But the time of his evolution presents one of the likely phase of human evolution connected with the water.

      1. Veronica, sorry for answering Bridget – I’m not used to comment here at anthropology.net – but it was meant for you.
        What you’re writing above is largely irrelevant. I’ll try again:
        H.erectus-ergaster-modjokertensis-georgicus-etc.-like fossils turned up “suddenly” 1.8 Ma from Java to Georgia to Algeria to Turkana – all in connection to the sea & next to edible shellfish (IOW, Dmanisi was apparently not the origin). This sudden appearance might have to do with sea-level changes at the time – they might have been littoral since longer – we don’t know.
        Later erectus-like people went even further: England, Angola, the Cape, Flores… – always along the coasts & next to shells – and from there inland along rivers.
        All these had pachyosteosclerotic skulls, which are exclusively seen in slow & shallow full- or part-time divers. If humans are animals like all others, there’s no reason why erectus-like people should be exceptions.
        IOW, it’s ridiculous to think erectus-like ran over the plains (cf endurance running nonsense), they simply dived frequently for sessile littoral foods, but of course also collected waterside foods, eg, turtles, drowned ungulates, stranded whales, cattails…
        Regular fishing was probably later: sapiens & presumably neandertals.
        Okidoki? Is it clear already?

        1. Really don’t understand your problem, Marc. Your first notion about, as it seems, your favorite topic, or better said the fixed idea of interest, was an answer to Bridget, who was answering Deborah, trying convincing her that till some extent of aquatic stage in human history is obvious (my opinion is there were more stages like this, if you like to know it). I was not participating in their debate at all, so it could not be mention to me! Deborah argued against aquatic stage or seashore life of humans, so she is probably the only one who would like your long explanations. Otherwise I really don’t understand why you bother to explain something not unknown so largely here. It is a topic about loss of human hair, have you realized? It is very good to mention this important thing, but no one argues with you, have you realized? I was replying to you only to correct your statements, which were in particular things wrong. But there is no one here to disagree with pachyostosis including me, which is, as I already mentioned, usually used as the SUPPORT of the aquatic phase theory, not as the opposite. So if you like to put arguments for this hypothesis, I just think you chose the wrong place.

          Final note about h. erectus from me: as I have tried to sketch out, there are quite serious differences in particular h. erectus skeleton findings, also regarding pachyostosis. It is very likely (oh no, it is definitive, of course, as well as in neanderthals, sapiens, etc.) his lifestyle varied altogether with his specific area of living. There is no single proof he did / did not fishing, so everything said to this is only a speculation. He definitely had all abilities to do it. Bye Marc.

  47. “It is a topic about loss of human hair, have you realized?” Veronika

    I agree. Why and how did the human line mostly lose the typical primate coat of hair, and why do the remaining tufts & long scalp hair (which is genetically prone in many to balding in adulthood) exist in some areas of the body but not others? I think I have answered these questions above, (without losing track of the primary topic).The most parsimonious explanation is that human ancestors turned their ‘bowl nests’ inside out.

    1. I like what Mark said above in one comment. We know the ancestors of humans began walking upright as they left the jungle as Africa dried out more, our gait is four times more energy efficient than a chimpanzee’s (on land). Also, it reduces overall body area exposed to sunlight, with our scalp receiving the most (and maintaining its hair as protection). We also know that humans are some of the best distance runners on the planet. It seems to make sense that along with the dietary shift to include meat, our ancestors performed persistence hunting (stalking a prey until it tires/overheats) and long distance scavenging. So, being in hot environment and running so much, naturally humans built up a lot of heat, and being hairy probably didn’t improve their chances of surviving heat stroke. Along with sweat glands and the ability to breath through our mouths while running (which both improves air flow and removes excess heat), it seems like the loss of hair to keep cool is the most plausible theory.

      Some people have argued that other animals live there with fur, so that can’t be it. But those animals aren’t such natural distance runners as us.

      1. Human ancestors have been orthograde (facultative upright bipeds) since the Morotopithecus mutation ~20ma (see Aaron Filler, The Upright Ape), and gradually improved metabolic efficiency, speed and carrying capacity, while sleeping in canopy owl nests and then in 5.2ma in ground dome huts in the tropical rainforest belt.

        The ‘dynamic activity’ theorists focus on jogging on wide open ground or wading/swimming in open water while ignoring the night-time predators and weather extremes that fur (or dome hut leaf shingles) protects against during the absolutely necessary nightly static sleep.

        If sustained exercise caused body hair loss, surely tiny human infants would be as hairy as ape infants, and only lose this body hair as they begin hunting, but that’s not the case. Actually the opposite, the persistence hunters tend to be the hairiest people of the camp.

  48. i am not studying medicine, but i do know that abundant body hair is a dominant trait.Now, how does that explain that humans shed their hair over time? shouldnt it be the other way round?

  49. correction to my last comment: canopy bowl nest, not owl nest.

    Article on body lice claims 7ma last common ancestor of 3 lice:

    Genome Biol Evol 4(11):1088-1101 doi 10.1093/gbe/evs088 open access
    Evolution of extensively fragmented mitochondrial genomes in the lice of humans
    Shao R, Zhu XQ, Barker SC & Herd K 2012

    Bilateral animals are featured by an extremely compact mitochondrial (mt) genome with 37 genes on a single circular chromosome.
    The human body louse Pediculus humanus, however, has its mt genes on 20 mini-chromosomes.

    We sequenced the mt genomes of 2 other human lice:
    – the head louse Pediculus capitis &
    – the pubic louse Pthirus pubis.
    Comparison among the 3 human lice revealed the presence of fragmented mt genomes in their LCA ~7 Ma. ..

  50. The definition of a mammal is a warm-blooded vertebrate animal that possess Fur or Hair.

    Fur is a soft hair that grows close together to act as an insulator/protective layer.

    Hair is a fine threadlike strand growing from the skin of mammals, It can be quite thick and coarse, to very thin and barely visible.

    Humans are COVERED in hair, Our entire body is literally fuzzy because of the incredibly small and incredibly fine hairs on it called Vellus hair, These are barely visible unless actually looking for them, Because of this hair that covers our bodies, we are one of the hairiest primates there are if not the hairiest, It may not be entirely visible, but it’s still hair. So your entire basis of calling us Hairless is unfounded. Other primates have thicker hair, while visible actually has less dense growth per square centimeter/inch than our own.

    Hairless means HAIRLESS, BALD, NADDA, NONE etc…

    Your entire post here should be on why our hair is so fine and dense and why it only grows in certain regions compared to other primates. Why we also have several different types of hair that grow compared to other mammals or primates.

    I can start you off with a bit of research… In a study that was done, People that have had the fine hair on their body shaved off are almost 90% less likely to feel a bug/parasite crawling over that area of the skin. So it would seem that these hairs have a role to play in our sense of touch. It also plays a minor role in helping perspiration as well as heat retention.

  51. Long heads of hair and beards would be in contrary to the aquatic theory.

    Lack of body hair i think is got to do with hunting in the open savanna, as humans pre-humans could not regulate heat loss by panting like other predators big cats dogs etc, the only way to regulate heat was through the body , and it wouldn’t been a very sufficient system if there was thick coat of hair. sweating cools down the body when it hit the atmosphere, The other adaption for lack of fur/hair was the darkening of the skin to protect against the sun.

  52. Still the same repetitions without any evidence, mostly because Dart found the Taung fossil (who in his opinion was a human ancestor) in what he thought had been a dry environment (later Tim.Partridge showed Taung lived in a humid environment).
    A little bit of common sense please:
    – Long hairs & beards are seen in lions lion tamarins, sealions, bearded macaques etc. They in no way contradict a littoral theory.
    – Sweat = water + salt = scarce in savanna.
    – Abundant sweating is seen in overheated sealions on land.
    – Fur reduction is seen in tropical semi-aquatics. Human ancestors were no exception: Pleistocene Homo dispersed along the coasts as far as Flores, Pakefield & the Cape.
    – Human Evolution conference London 8–10 May 2013 with David Attenborough & Don Johanson.
    – “Was Man more aquatic in the past?” eBook
    – guest post at Greg Laden’s blog

  53. I think the reason for the loss of body hair in humans has a very simple explanation.
    It coincided with the onset of superstition and as we all know, superstition still flourishes and it’s now considered normal to believe that invisible, supernatural entities are living in the sky. Early man’s primitive intellect led him to believe that hairiness was devil-like and that lack of body hair was more god-like so this was selected for when choosing a partner and even possibly infanticide towards hairy babies.

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