Anthropology.net

For many years, the use of fire has been central to the discussion of human evolution. When was fire first controlled, and when was it first actually made by man? These are questions that rise again and again, but with scant early proof. Recently in the online journal Fire Ecology, an environmental scientist discusses what could be the earliest regular source of fire for our earliest ancestors (or potential ancestors).

Maybe an unconventional source for speculation on human origins, Michael Medler is an associate professor of environmental science at Western Washington University.  His paper can be broken into two sections, one based on reasonable observations in his specialty, and the other of speculation outside of his field (which in all fairness, the author sort of points out himself).

For millions of years in the African Rift Valley, volcanic activity went through periods of relative stability. Early groups of hominins going back millions of years would have been had access to lava flows, and in turn the benefits of heat and fire. Could it have been here that the earliest hominins started to add fuel to keep a fire going, keeping close to it for protection or warmth?

Homo erectus, a species that likely moved out of Africa aided by fire.

Maybe– but as Medler points out it is impossible to tell archaeologically. It is difficult enough for experts to determine fire usage in later instances, let alone millions of years ago in Africa.  If the earliest fire-users were in close proximity to lava flows, it is possible that the evidence would never be found. If charred bones turn up, who is to say that they were not burned by a natural fire? For now, this type of theory will remain almost strictly without archaeological evidence based simply on the principle of poor preservation.

However, the author states that there can be strong circumstantial evidence in support of his claims. If times of volcanic activity coincide with the presence of hominin species, this could perhaps be considered suggestive. As one example, Medler notes a period consistent with the emergence of Homo erectus.  Before 1.8 million years ago, there was a time of volcanic activity that was stable for about 200,000 years. This period overlaps with both the appearance of Homo erectus and their dispersal out of Africa—where knowledge of fire would have been an important factor.

There were many parts of Medler’s paper that had me questioning its integrity, namely the section on the use of tools.  While the sections that had me shaking my head were under the subheading “speculations and just so stories” I do not think this excuses him from their inclusion. He writes– without citation—-about how hand axes would have been more useful in cutting fuel than meat.  Where he got this information, I’m not really positive.

While this article does not seem to have been done in a circle of paleoanthropologists, the core ideas should get you thinking. Looking at volcanoes as a potential source of fire is intriguing, mainly because of the consistency with which they are present historically. Perhaps the next paper will have an anthropologist as a co-author.

By Matthew Magnani

Medler, M.J. 2011. Speculations about the effects of fire and lava flows on human evolution. Fire Ecology 7(1): 13-23. doi: 10.4996/fireecology.0701013

Carol Ward1, William Kimbel, and Donald Johanson have published a paper in Science on the arch seen in a newly discovered fourth metatarsal of Australopithecus afarensis (AL 333-160). A lot of the popular press are publishing misleading headlines that this proves bipedalism in australopithecines. No, we’ve known they were bipedal — we just didn’t have a true idea as to what extent they were bipedal. So a find like this helps investigate the degree of bipedalism.

AL 333-160 left fourth metatarsal in dorsal, lateral, medial, plantar, and proximal views.

How does this tell us how bipedal A. afarensis were?

) Box plots of angular relations of the proximal and distal metatarsal ends to the diaphysis in chimpanzees, gorillas, humans, and AL 333-160.

If you’ve ever had the pleasure of visiting a podiatrist, you’d know flat feet are not conducive to bipedalism. The two-way arch helps support upright walking and distribute recoil force. Other great apes like, chimps and gorillas have flatter feet than us. The authors of this paper confirmed this by comparing the fourth metatarsal of chimps, gorillas, and humans to AL 333-160.

On all their comparisons, AL 333-160 fell within range of humans. There were some occasions where there’s a lot of gray area which I’ll address later. Nonetheless, to the right you can see the best comparison, in my opinion, which the comparison of the arch of the diaphysis of the bone between the two species. You can have a look at the rest of the figures here.

The problem I am seeing here is that this metatarsal is not Lucy’s (AL 288-1). AL 333 is designated to fossils from the site where the “First Family” came from and not the same  locality as AL 288. Nonetheless, they are not the same individual. Kimbel is quoted in the BBC News, saying,

“Lucy’s spine has the double curve that our own spine does,” Professor Kimbel said.

“Her hips functioned much as human hips do in providing balance to the body with each step, which in a biped of course means that you’re actually standing on only one leg at a time during striding.

“The knees likewise in Lucy’s species are drawn underneath the body such that the thighbone, or femur, angles inwards to the knees from the hip-joints – as in humans.

“And now we can say that the foot, too, joins these other anatomical regions in pointing towards a fundamentally human-like form of locomotion in this ancient human ancestor.”

This is a flawed association to make; a form of what I would call confounding bias. We don’t have Lucy’s 4th metatarsal to see what it looks like and unfortunately we don’t have the rest of the this specimens skeleton to say it looked like Lucy’s. In fact, we have very little australopithecine appendicular and skeletons other than AL 288-1 (most notable are AL 129-1 and STS 14). So how can Kimbel say that the foot joins other anatomical regions when we don’t know what the other regions really looked like?

See, the n of this sample is 1. Looking at the intervals in the figures, especially Fig 3 & 4, there a a significant amount of variation in humans and chimpanzees that overlap. Chimps aren’t bipedal but we are. So imagine you are a paleoanthropologist way in the future looking at one metatarsal of a now-current then-ancient chimpanzee way and comparing it to a humans — surely you could make the same conclusion as these three have. And herein lies the big issue with sensationalism… as is the problem often in paleoanthropology, we just don’t have many comparative samples but people want definitive conclusions.

Ward, C., Kimbel, W., & Johanson, D. (2011). Complete Fourth Metatarsal and Arches in the Foot of Australopithecus afarensis Science, 331 (6018), 750-753 DOI: 10.1126/science.1201463

Very rarely is an entire family group of hominins buried and fossilized at the same time. It is even rarer for paleoanthropologists to discover such an assemblage. Fortunately for science but unfortunately for the hominins, caves occasionally collapsed on entire social groups.

Map of El Sidrón

At a site known as El Sidrón in Spain, excavations have been ongoing since 2000. To date, 12 Neandertals have been discovered in a context that points to a single geological event, circa 49,000 years ago. A group of 12 Neandertals is consistent with previous estimates of around 10 individuals per group.  At least six adults, three adolescents and four younger individuals were buried at once, most likely during a storm. The cold conditions of the cave system and immediate burial of the remains not only preserved the bones well, but were also ideal for DNA.

The remains were sexed based on both morphology and DNA analysis. After sex was determined, anthropologists identified the different Neandertal lineages based on mitochondrial DNA. Several of the adults were found to be male, and the other three female. It was discovered that all three males belong to the same matrilineal group, while each respective female has a different haplotype. When compared to modern Europeans, the authors noted that there is significantly less genetic diversity within the mitochondrial genome.

These results strongly imply that Neandertals exhibited patrilocal mating behavior. Females were the ones who would have changed family groups, not males. This type of insight into an extinct species is unique, thanks to the quality of DNA preservation available at El Sidrón.

Another interesting point of discussion in the study relates to Neandertal interbirth interval. One of the females was linked by DNA to two of the younger individuals, approximately several years apart in age. If the anthropologists are correct about the relationship, this puts the interbirth interval for Homo neanderthalensis at a value similar to hunter-gatherer groups today. This data, if replicated with other Neandertal individuals, could eventually dispel differential reproduction as a potential cause for Neandertal disappearance.

Knowing about Neandertal group dynamics could provide crucial clues as to why they went extinct. Future analysis of the remains recovered at El Sidrón will no doubt give more insights into our closest extinct relatives, and perhaps even why Homo sapiens flourished and Neandertals declined.

By Matthew Magnani

Lalueza-Fox, C., et al. (2011). “Genetic evidence for patrilocal mating behavior among Neandertal groups.” PNAS . January 4, vol. 108 no. 1 250-253.

Hans-Peter Uerpmann of the University of Tubingen has lead a team excavating the Jebel Faya site in the United Arab Emirates, right near the Straits of Hormuz. They’ve found 125,000 year old stone tools that look like early modern human tools from East Africa around the same time. They’ve published their findings in today’s Science, under the title, “The Southern Route “Out of Africa”: Evidence for an Early Expansion of Modern Humans into Arabia.”

The current understanding is what we know as anatomically modern humans (AMH) originated in Africa about 250,000 years ago. The oldest Home sapiens, known as H. sapiens idaltu, was found to be 160,000 years old, found at the Middle Awash site in Ethiopia. Then between 80k-100k years ago, modern humans began appearing in the middle east, as remains from sites like the Qafzeh cave in Israel have yielded. Most agree that AMH stayed in Africa and about 140,000 years ago they began migrating out. There was an exception, a colonization remained or failed in Israel about 100,000 years ago.

One of the hand axes from Jebel Faya, UAE (Photograph courtesy Science/AAAS)

These hand axes, pictured above, show a pattern of flaking distinct from that made by Neandertals and also dissimilar to those by ~100,000 year old Israeli tools. They are two sided and very similar to stone tools seen only in early Africa.

What this means is early humans left Africa 20,000 years earlier than thought. Just how did they do it? 130,000 years ago, there was a window of climate change. They figured this out by using luminescence dating to determine the age of sand grains buried with the stone tools. Luminescence dating is a technique that measures naturally occurring radiation stored in the sand. The data showed that 130,000 years ago, the Arabian Peninsula was relatively more warm which caused more rainfall, turning it into a series of lush habitable land. During this period the southern Red Sea’s levels dropped and was only 2.5 miles or 4 km wide. This offered a brief window of time for humans to easily cross the sea and cross the Peninsula to opposing sites like Jebel Faya.

Does this study tell us that modern humans left Africa, into Arabia and out from there? It is most certainly a possibility. However, these axes could be of an abandoned migration like the site in Israel I’ve mentioned. I say that because no genetic clade, be it from mitochondrial, Y-chromosome, or somatic genome, shows an earlier divergence of modern humans from Africa earlier than 60,000 years ago. At the very minimum a find like this tells us humans left Africa a bit sooner than we thought, but does not really tell us that these were the humans that helped seed the Eurasia.

Armitage, S., Jasim, S., Marks, A., Parker, A., Usik, V., & Uerpmann, H. (2011). The Southern Route “Out of Africa”: Evidence for an Early Expansion of Modern Humans into Arabia Science, 331 (6016), 453-456 DOI: 10.1126/science.1199113

Neandertals have long been touted as a species with “hyperarctic” adaptations. Their stout proportions and shortened distal limb segments are often explained to conserve heat. Similarly, the Neandertal cranium is traditionally said to be cold adapted. An article released on December 22^nd in the Journal of Human Evolution challenges these traditional notions, specifically those about Neandertal nasal adaptations.

The Neandertal nasal apparatus has conventionally been cited as cold adapted mainly because of the enlarged sinuses. The authors of this article, among them Chris Stringer, cite evidence that larger sinuses are not in fact typical of cold weather mammalian species.

Through observation of human populations and studies on other mammals, cold weather is more highly correlated with smaller sinuses. That is, animals from more northerly locations typically have smaller sinus cavities. As an example taken from lab studies, rats raised in colder conditions also show smaller sinus cavities.

But are Neandertal sinuses even large, as is typically maintained? The authors of this paper argue that there is nothing large about them. Through examination of Neandertal remains, the sizes of the frontal and maxillary sinuses actually fell within the range of Homo sapiens from temperate climates.

The Forbes’ Quarry Neandertal (left) and H. sapiens skulls. Frontal sinus in purple, maxillary sinus in red. Photo from Rae et al., 2010.

This study is very suggestive that Neandertal nasal anatomy is not due to cold weather adaptation. To be cold weather adapted, the sinuses would be smaller and not larger, as many anthropologists have maintained since the first remains were discovered. Not only are the sinuses not small, they are not large- which speaks to a larger problem. How many other basic assumptions do we take as fact just because they have been around for so long?

If not cold weather, what could have caused the differences in facial anatomy between H. neanderthalensis and H. sapiens? The authors of this paper do not offer many answers, but offer a couple of possibilities. Differences in masticatory stress (utilizing teeth as a tool, for example), or genetic drift are two potential reasons discussed.

This paper may be taking another step in overturning traditional understanding of Neandertals as a cold weather species. Generations of anthropologists have passed knowing that Neandertals differed in facial anatomy due to cold weather adaptation, unsubstantiated by data.

Rae, T.C., Koppe, T., Stringer, C.B. (2010).  The Neanderthal face is not cold adapted.  The Journal of Human Evolution. Article in Press.

Image via Wikipedia

A Homo floresiensis premolar will be drilled, and DNA extracted, according to a Nature News piece passed on by Razib, John Hawks, and Dienekes. This is not the first attempt at extracting hobbit DNA, the news article explains,

“Five years ago, two teams, one from ACAD and one from the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany, attempted to recover DNA from another H. floresiensis tooth excavated in 2003. Both attempts failed.

Now, a team led by Christina Adler, a geneticist at ACAD, has found that standard sampling procedures could be responsible for the failure to get DNA from the hobbit and some other ancient specimens.”

I’ve been out of the loop for a couple years and have lost track on the advances made in ancient DNA studies. I do remember there was a big hub-bub regarding contamination from excavators and degradation of DNA. Maybe some of the new techniques overcomes these problems.

The lead, Adler, recently published a paper on the advances, titled, “Survival and recovery of DNA from ancient teeth and bones.” Again, I don’t have time to read it and give you a summary because I am studying for my board exams. It seems like the paper advises extracting DNA from the cementum of teeth which has way more DNA than the normal source of aDNA, dentin… But if you’re curious about ancient DNA sequencing, this should be an interesting read.

Nonetheless, it should be very interesting to see what comes from this attempt. I wish the team the best of luck and eagerly await the results.

Well, I feel somewhat vindicated. Remember the post where I criticized hominin cut marks from over 3 million years ago? Others have also had an eye of suspicion and have published their concerns in PNAS this week.

I was wrong in considering the croc marking differential to the cut marks. But I was not wrong in thinking they author of the original paper made the wrong conclusions. The authors of this new paper raise up an even more logical explanation, and carried out a more thorough analysis. Here’s part of their argument from the abstract,

“The Dikika research group focused its analysis on the morphology of the marks in question but failed to demonstrate, through recovery of similarly marked in situ fossils, the exact provenience of the published fossils, and failed to note occurrences of random striae on the cortices of the published fossils (incurred through incidental movement of the defleshed specimens across and/or within their abrasive encasing sediments). The occurrence of such random striae (sometimes called collectively “trampling” damage) on the two fossils provide the configurational context for rejection of the claimed butchery marks. The earliest best evidence for hominin butchery thus remains at 2.6 to 2.5 Ma, presumably associated with more derived species than A. afarensis.”

Trampling vs. Cut Marks (The image in A is courtesy of R. Blasco and J. Rosell. The images in B, D, and F are modified from McPherron et al.)

Looking back at the comment thread, I got a lot of flak. Aside from being wrong about the croc markings, I won’t deny that my post was inflammatory and incited a lot of the response. But many who know just a bit about the fossil and archaeological record, may find it extraordinary to believe australopithecines were using stone tools to extract food from flesh and bone from ‘indirect’ evidence. Of more concern was the lack of exhaustive exploration into other possibilities.

I remember as an anthropology undergrad one of my professors designed a hands-on experiment for us. If memory serves me correctly, this was for a zooarchaeology class. She acquired some beef bones from the local butcher and gave us stone tools. We were instructed to extract the marrow from the bones. We hammered the afternoon away.

Part of our assignment was to use different techniques and tools. We could cut, saw, abrade, chisel, etc. After the mess was done we compared our extractions from prehistoric samples. This comparative approach allowed use to systematically compare how we modified the bone to how possibly prehistoric individuals modified bone.

The authors of the current PNAS paper did something similar. The hypothesized that trampling could have created similar modifications as seen on the 3.39 million year old Dikika bones. And what did they do? Well they got some bone and experimentally setup some trampling experiments. As one would expect, cut marks would have a \/ shaped incision. Incidentally, the bones from Dikika show a \_/ flat bottom morphology. The authors write,

“Ninety-six percent of experimental trampling grooves display a broad-based, open cross-section with the aforementioned shape, versus just 4% of experimental grooves inflicted by simple (i.e., unmodified) stone flakes used to cut meat from bones. In addition, curvy and sinuous groove trajectories characterize nearly 70% of experimental trampling marks,compared with just 10% of experimental cut marks created with simple flakes (11). Together, these experimental results provide a robust actualistic context to evaluate illustrated marks F, G, H2,and I on DK-55–3 as high-probability trampling damage and not stone tool cut or percussion marks…”

I wonder what happened to good science?

What happened to the scientific method?

Did we not learn how to set up experiments and carry out analysis?

How can a paper make all the way into Nature and not exhaust all the possibilities?

These are not rhetorical questions. I am seriously asking it. I honestly feel that there is something rife in paleoanthropological studies lately. I must sound like a broken record to say yet again, too often are papers published in haste and for fortune and glory… All which compromise the validity & ethical responsibility of the science.

Domínguez-Rodrigo M, Pickering TR, & Bunn HT (2010). Configurational approach to identifying the earliest hominin butchers. Proceedings of the National Academy of Sciences of the United States of America PMID: 21078985

Several views of a human jawbone and molars found in a Chinese cave.

National Geographic is running news that Erik Trinkhaus and others have published the findings of the oldest modern human outside of Africa, specifically in China. Not much is given on the locality and specifics of the fossil, but the article does state that the fossil mandible fragment and teeth are 60,000 years older than any other modern human fossil. That leads to some curious questions of interbreeding with other Homo species and curiosities about the presence of modern humans that did not ‘act’ modern… In other words, the archaeological record isn’t quite on the same page.

Hawks hasn’t posted on the paper and find yet, but he is quoted in the National Geographic article saying the mandible dimensions are within range of both Neandertals and modern human. Unsurprisingly, the Out of Africa theory is challenged. I still don’t know what to think of it all, the chin does look very robust.

The PNAS article is not yet published at the time of the National Geographic writing and me blogging this post. Seems like people are still jumping publication embargoes. I shouldn’t have to call out what a cheap shot it is to have sensationalist news getting out before the first hand reports do. I guess things will never change. So until I get my hands on the real paper, I’m just calling it as others are reporting it.

A colleague of mine has developed a new online human fossil record, in the likes of my own database of fossils. The project is Fossilized.org and although it is in beta, it has some remarkable features already. I am particularly impressed with the phylogeny plot view, which offers a chronological color coded map of many important hominin fossils. What’s unique about this view how it helps visualize localities different hominin species lived and spread throughout the world. Here’s a sneak peak….

Fossilized Phylogeny View

Furthermore there is an interesting history of prehistory section the database, which I have never seen be done before, as well as a geochronological timescale. The latter view offers a way to visualized oxygen levels throughout prehistory. Be sure to check out Fossilized.org and poke around. If you are an educator, let your students and colleagues know about this resource.

Personally, I’ve constantly advocated for more online resources like this. To my knowledge, there isn’t one as focused on localities. So, I’m glad to see there’s another database of the human fossil record out there, especially one that offers up some new features and more complete dataset than some currently out there.

Every time big anthropology news has come out in the last year or so, I’m too busy and drowned under the sea of books and notes for my upcoming exams to immerse myself in it. This happened with Ardipithecus last fall, and now with the draft of the Neandertal genome coming out tomorrow, I can’t help but feel a bit left out. The complete mitochondrial Neandertal genome was released a little under 2 years ago… and now because of high throughput sequencing technology, the draft genome is now complete.

Currently, Science has put up a special section of their website dedicated to this. The news agencies are having issues with embargoes and what not, they put up articles and then take them down. But the word is out, Green and Pääbo’s project to sequence the Neandertal genome is out and there are some interesting findings:

• The comparison of 3 Neandertal samples to 5 modern human genomes showed that Neandertal genome is closer to some populations of modern humans than others
• About 10 loci had distinctly non-African hallmarks
• There’s an attributable 1-4% Neandertal ancestry to non-African modern human populations

There’s a lot more behind this all than I really have time for, unfortunately. So be sure to check out Razib, John Hawks, etc. for all the goodies.