Do we really need to consider turning everything upside down by considering the existence of a human ancestor for the apes? This suggestion definitely has the quality of blasphemy against religious doctrine. It just feels wrong and goes against our deeply held beliefs and understanding of the world.
However, this is exactly where the evidence leads.
Overall, I don’t expect that the entire anthropology community will suddenly abandon everything that has been taught for decades. However, my point is the following:
- We see the spine anatomy of a hindlimb supported upright ape in Morotopithecus, Pierolapithecus, Oreopithecus. The data is compelling and extensive – and I have detailed it in technical raw data form in my book: Axial Character Seriation in Mammals, which republishes my Harvard PhD Thesis. The underlying patterns are extracted and synthesized in my recent PLoS ONE paper “Homeotic Evolution of the Mammals, Diversification of Therian Axial Seriation and a Morphogenetic Basis for Human Origins” and in my Neurosurgical Focus article. The context in evolutionary theory is explained in my recent book “The Upright Ape: A New Origin of the Species” which has a foreword by David Pilbeam – currently Dean of Harvard College and certainly one the most knowledgeable and experienced paleoanthropologists in the world.
- We have evidence of an upright hindlimb supported Orrorin based on the femur and Sahelanthropus based on the skull.
- There is no convincing fossil evidence at all of a non-bipdeal hominoid outside of the proconsulid group.
- We have an early outgroup whose infants have innate bipedal walking (see the video Hominiform Progression). The Siamang video is interesting because of the innate bipedalism. As I point out in the video, John Fleagle has seen young siamangs of this age walk bipedally high in the canopy in Malaysia.
It is typical to say that all of this is irrelevant and misleading and should be ignored. There was a quadrupedal common ancestor for chimps and humans and the human lineage suddenly and majestically stood up about 5-6 million years ago. However, I feel that there is no a priori reason why we must ignore all of the evidence for early bipedalism.
None of the skeletal evidence can ultimately distinguish between “short bursts” and long distance bipedalism as Kambiz points out in his post. My focus is on the character state and whether the crucial anatomical basis is a shared derived feature of a hominiform clade.
It can certainly be said that the siamangs only engage in bipedalism for short bursts, but that is also true of their brachiation. Similarly, the chimps and gorillas knuckle walk and the orangutans fist walk only in short bursts. However, the important point is that chimps, gorillas and orangutans seem to locomote in diagonal posture more than 90% of the time and only occasionally deploy a short burst of bipedal walking. I would argue that they have very bad spinal architecture for bipedal walking. On the other hand, hylobatids use bipedalism 100% of the time when they locomote on the ground no matter how long the burst of activity. If a hylobatid has to travel a long distance on the ground – it does not lapse into a quadurpedal gait – it just keeps walking bipedally. There is an important difference in the role of bipedalism as deployed by hylobatids and hominines as opposed to what we see in chimps, gorillas and orangutans.
This would be a morphogenetic origin for upright bipedal walking rather than an adaptive origin. Essentially, the origin of upright posture was not driven by any ecological scenario, but rather occurred suddenly as a result of a morphogenetic mutation in the Pax genes. Various descendant forms will have lived in various environments with variously optimized versions of primary upright bipedalism on large horizontal arboreal supports and on the ground.
It is certainly easier to assert that Morotopithecus was upright and hindlimb supported – based on spinal anatomy – than to prove it was primarily bipedal or a long distance walker. 
However, this is where the video showing the baby siamang learning to walk bipedally is relevant. Yes, you could argue that innate bipedalism evolved independently in parallel in hylobatids and hominines, but is also reasonable to consider that since this is so unusual, that it reflects descent from a common ancestor that had this feature. Essentially – an eight month old Morotopithecus baby would do the same thing that we see in the two descendant groups (hominines and hylobatids) – the baby would innately begin to walk bipedally as it’s primary locomotor pattern.
So – if the chimp-human split did take place 6 million years ago (as the molecular data suggests), then what do we do with Sahelanthropus which many believe was a full time upright biped but which lived 7 million years ago?
If you want a slow gradual evolution of bipedalism, you need to push the chimp human split back to say 8 million years. However, there is an alternative explanation. Upright bipedalism was already the primary means of locomotion in the common ancestor of chimps and humans – Sahelanthropus is ancestral to both lines.
What defines a “human?” I have taken the position that it is a body plan (bauplan). Most of us have accepted that early Australopithecines whose brains and skulls were chimp-like, should be considered human and not ape. When you find a fossil such as Sahelanthropus that has a “chimp-like” skull from the point of view of its face and brain, but has the skull base of a human (and presumably upright bipedal post-cranial anatomy) – how can you tell from the fossil if it’s an ape or a human?
The Hennigian cladistic approach lets us say that the isolation point between the chimp and human lineages – where hybridization became impossible – is the origin point of humans. However this means that the definition is arbitrary since ape and human would pretty much look identical at that time.
Another alternative is to stick with our current definition – a hominoid whose anatomy reveals that it is primarily an upright biped is a human. I have proposed the term “hominiform” to refer to a clade of hominoids that share the Morotopithecus spinal transformation (septo-neural transposition – in which the dorso-ventral plane of the body flips from ventral to the spinal canal to a new position dorsal to the spinal canal) and the styloid process is converted into a neomorphic hominiform lumbar transverse process. The 
synapomorphies would include innate bipedal walking in the infants.
Among hominiforms we have primitive “eubipedal” types (most Miocene and Pliocene fossil hominiforms, the hylobatids and the hominines) and derived “metabipedal” types (lineages of chimps, gorillas and orangutans) that have abandoned bipedalism as their primary locomotor pattern on the ground.
Sahelanthropus appears to be a human species that is representative of species in the line of ancestry to both the chimpanzees and hominines.
Aaron Filler, MD, PhD
58 Comments
December 15, 2007 at 1:53 pm
[...] talks about human evolution, and how it was possible that modern apes may have had a human ancestor! […]So – if the chimp-human split did take place 6 million years ago (as the molecular data [...]
December 16, 2007 at 12:21 am
For what it’s worth I had this posted a couple of weeks ago:
http://remotecentral.blogspot.com/2007/12/in-defence-of-human-evolution-first.html
A couple of comments I made there may interest you:
“The species has been classified as Sahelanthropus tchadensis and it appears to be ancestral to the Australopithecus genus (and so to us). The big question is; is it also ancestral to chimpanzees and gorillas?”
And “We can presume the common ancestor of humans and African apes was a bit like an Australopithecus or Ardipithecus and even more like Sahelanthropus. Chimpanzees may indeed be the least changed from the ancestral population and so possibly the common ancestor was like a chimpanzee. But we can’t say that humans evolved from chimpanzees. For all we know chimpanzees may believe they have evolved from us. Some people believe the unusual way the African apes move on the ground (knuckle-walking) indicates the apes may in fact have evolved from more upright-walking ancestors.”
December 16, 2007 at 12:06 pm
“This suggestion definitely has the quality of blasphemy against religious doctrine”
That’s how cranks start their marvelous and “revolutionary” claims against the Establishment. Pity for Anthoropology.net. This kind of fringe science is ruining the site :-(
December 17, 2007 at 7:13 am
It’s not fringe science. You can take the results of research at the Harvard Peabody Museum, accepted as a PhD Thesis, and a peer-reviewed publication accepted by one of the leading scientific journals – PLoS ONE and call it “revolutionary” “a pity” and ruinous – but that just shows fear of change. Can’t we all just keep the findings of science the same way they all were when I first learned it? If the new data doesn’t fit the old theories – I know you’re one of the advocates for ignoring an burying the data. But you are certainly not alone in that. Fortunately there is no ultimate comfort for scientists who fear change.
December 17, 2007 at 8:11 am
I’m Catholic. I can’t imagine why conclusive proof that apes evolved from hominoids would contradict Catholic teaching or doctrine. If you maintained that apes evolved from homo sapiens, that would be interesting.
December 17, 2007 at 1:43 pm
“Fortunately there is no ultimate comfort for scientists who fear change”. Perhaps not, but history shows that the comfort can last for an unbelievably long time.
December 18, 2007 at 1:38 am
“You fear change”: another guaranteed crank sentence. I hope we don’t have to read the typical auto-comparisons with Galileo.
“I know you’re one of the advocates for ignoring an burying the data”
Yes, I am an anti-scientific super villain. You are the galilean hero.
December 18, 2007 at 3:27 am
El PaleoFreak – not to worry. Fortunately, a wide array of paleoanthropologists and evolutionary biologists have actually read the PLoS ONE paper and other publications and it has all been well received in the academic community if not universally accepted. I have a podium presentation at the next Amer. Assoc. of Phys. Anthro meeting. I’m certainly not having trouble getting published. One of my books is from Oxford University Press -so no I won’t be making any auto comparisons with Galileo. I was more surprised by your outburst about this being crank fringe science – presumably without actually bothering to first read any of the primary data. I apologize if you actually have read the material, but I understand you may not have time to go beyond the opening paragraphs of the blog.
December 18, 2007 at 4:40 am
Three days ago your work is like “blasphemy against religious doctrine”, going “against our deeply held beliefs and understanding of the world”. Today it is “well received in the academic community if not universally accepted”.
Wow! That’s probably the fastest scientific revolution in History. Congratulations!
A 21 million years old macro-mutant individual was the first human. Chimps and gorillas evolved from humanity. Universally accepted… OK.
December 18, 2007 at 6:38 am
If this evidence holds up, I think it can be a corrective to the typical human need to consider ourselves the “peak” of evolution. It might better convince at least some people that we are part of life, not the end result of it, and all that that implies. Such thinking is as blinkered as that of those who thump for intelligent design, and conceals a secret prejudice in favor of that dangerous, gratifying notion, “progress,” still unpleasantly prevalent in our society. I will follow this with great interest.
December 18, 2007 at 7:33 am
El Paleo – I am very clear in making the introductory point that when you first hear this it has the feel of e a deeply held belief being challenged. I go on to point out that the data is leading this way. Because most scientists go through the data before attacking, it has been well received. If you attack before you read the data then you are … well.. El PaleoFreak
December 18, 2007 at 9:15 am
Data, data, data. You keep talking about data. This is not about data, it’s about certain claims, and the pompose way they are made. It’s about particular interpretations and conclusions on certain set of data. The data don’t say we have to redefine “biped” or “human” concepts. The data don’t say anything about a macromutant ancient “human”. You are saying it.
December 18, 2007 at 3:26 pm
Brian. I agree totally with everything you wrote.
December 18, 2007 at 4:25 pm
Little doubt prof.Filler is correct in saying that the early apes c.20 Ma had an upright spine, but that doesn’t mean they were “bipeds”. Miocene apes are typically found in coastal/swamp/flooded forests (eg, Heliopith=Afropith, Austriacopith=Griphopith, Dryopith, Oreopithecus…), so they spent some time in the branches, some time in the swamp (as proboscis monkeys do & Ndoki gorillas, only more frequently), where the upright spine was obviously advantageous for wading on 2 legs & for grasping branches or fruits above the swamp & for hanging on the branches. This also explains many differences between monkeys & apes: tail loss, less lumbar vertebrae, larger size, broad thorax & breast bone, arms lateral of body, etc. For discussions of this “aquarboreal theory” (aqua=water, arbor=tree), see http://groups.yahoo.com/group/AAT
December 19, 2007 at 3:45 pm
I’m just a layman enthusiast, but I’ve always prefered this hypothesis of evolutionary “inertia” for human bipedalism.
Human wide shoulders and thorax also seem to make more sense (to me, a layman) as something that comes “directly” from arboreal ancestors which used to be hanging on and between branches, rather than something that would evolve following an upright posture. I can’t see why the broader shoulders would be an important/likely adaptation for upright posture or succeeding it; I think that we could do very well even with a upper body that was originally adapted to knuckle walking (but, in the other hand, it could have evolved as a by product of overall neoteny, I sloppily guess).
I think I got this thing of upper body more similar to “branch-hangers”‘ from Pilbeam’s “ascent of man”, which I think dates from when it was thought that the human lineage had split prior to orangutans, gorillas and chimpanzees. And, there’s also JH Schwartz, which probably points to similar things on anatomy, even though I prefer to ignore everything else he may say.
This “fake” quadrupedalism of chimps and gorillas also seems more likely (to me) to evolve convergently by natural selection, as quadrupedalism is more efficient in many aspects. Even chimps, however, perhaps bring some clues of a past bipedal gait. I’ve read something recent saying that some of them actually have more efficient bipedal than quadrupedal gaits, regarding energy comsumption. It’s something that varies individually with learining/practice, if I recall.
There was also a theory (unfortunately I don’t recall the theorist, but I think I’ve read about it in either Edey and Johanson’s “Lucy” or Foley’s “humans before humanity”) that chimps or maybe chimps and gorillas were initially more human-like (not specifying how more human-like, as far as I recall), and what happened was some sort of character displacement by natural selection. Wherever I’ve read that, it said that it’s no longer believed, but does not seem very bad to me.
I think that, despite of being somewhat less parcimonious the independent evolution of knuckle walking in chimps and gorillas versus evolution of upright posture in humans, when seen in a larger context it’s more parcimonious.
Evolution by natural selection – an onerous concept, as G. Williams put – is more evenly distributed by the lineages, and humans cease to be such a “deviation”, which differentiated exceptionally. A recent research actually suggests that chimps have evolved somewhat more than humans by NS anyway, which I think that also may favor this point of view.
And, furthermore, about the human-chimp split, how’s that deal with the 10 million years old gorilla, that was thought to possibly imply in a early split between humans and chimps? (due to molecular clock’s adjustments).
I don’t know if it was finally regarded as a necessary adjustment, but however, as far as I know, this anticipation of the split may be more in accordance with the fossil evidence we have (or once had, perhaps it changed by now), which used to point to an earlier split (~8Mya) than molecular data suggested (~5Mya).
So, seems that quite a few “outdated” ideas are becoming somewhat “fashionable” again.
December 21, 2007 at 11:57 pm
Hi, Im from Melbourne Australia.
Please find a completely different understanding of human origins—namely trees—seriously.
http://www.fearnomorezoo.org/trees/main.php
http://www.dabase.org/unique.htm
And yes human are essentially talking hairy primate shit machines.
December 22, 2007 at 3:13 pm
I am a zoologist and I developed, 20 years ago, a theory called “initial bipedalism” about the descent of apes (and other quadrupedal mammals) from bipedal human-like forms, that developed from originally erected aquatic forms. So I totally agree with Dr Filler’s assertion that chimps and gorillas have descended from early bipedal “hominiforms”!
December 22, 2007 at 6:11 pm
Wow!
Now the aquatic ape cr… er, people!
:o)
December 28, 2007 at 4:45 am
Actually the “data” (there’s that pesky word again!) has been demanding a new conceptual interpretation for a long time. A very long time. I’m only an “armchair” paleo freak myself, but I have browning notes of my own from 20 years ago where I wrote in the margins “if bipedalism didn’t evolve twice, then quadrupedalism had to.” We could of course just give up on explaining the fossil record, but what fun is that?
The finds of Ardepithecus, Orrorin and Sahelanthropus have made it clear for some time that the last common ancestor between chimps and humans was almost certainly a biped. How likely is it that the LCA stood up on two legs for the first time, just in time to immediately diverge into two lines, one of which immediately “reverted” to quadrupedalism? Either we’re looking at the fastest “do-over” in evolution, or bipedalism extends back further into antiquity.
Any sharp line we try to draw between humans and the other apes will always be entirely subjective. Bipedalism sufficed for many people for many years, but that’s out the window. The dust will be a long time settling.
December 29, 2007 at 6:29 am
Human uprightness implies much more than mere bipedalism. It is a unique feature characterized by the fact, that in the normal upright position all the centers of gravity of separate body parts (head, torso, upper arm, forearm, hand, thigh, lower, leg) are located in the same frontal plane, producing a unique pattern of overall mechanical equilibrium. This fact was already discovered at the end of the 19th century, by Braune & Fischer. Even H. Erectus or H.Neanderthalensis are lacking this pattern (as far as the head is concerned). See my book:
http://www.adonispress.org/developmental.html
December 31, 2007 at 1:57 pm
[...] Mangan says that smoking is good for your IQ (cheers from Udolpho, jeers from Ilkka Kokkarinen). It may be the case that apes are descended from what we might call human (it walked upright, and the apes [...]
December 31, 2007 at 4:18 pm
Title should be “A bipedal ancestor for the apes?” Present (sensationalist) title also implies that modern humans could interbreed with the common ancestor of humans and chimps, but modern chimps could not. And so on. These are sweeping claims I presume Dr. Filler is uninterested in pursuing.
December 31, 2007 at 5:35 pm
To omnivore – This is a question of definitions and I have addressed it more specifically in my blog on the Oxford University Press site – Redefining the Word Human: (http://blog.oup.com/2007/12/human/).
I am not saying “Homo sapiens” which is a species. We are talking about what to call an “animal” such as Sahelanthropus – is it an ape or is it an adjectivized human (e.g. “proto-human”) which is still “some kind of human.” We can also distinguish between “sapient human species” and perhaps “pre-sapient” or “pre-symbolic” human species. The problem comes down to the fact that Australopithecus afarensis probably should not be called an “ape.” These are obviously colloquial and non-cladistic terms, but I argue that they refer to our perception of body plan. We have dodged the issue by using definitions that require complex speech etc. but these clearly exclude the “early, ancestral, or proto-” human species.
Aaron Filler
December 31, 2007 at 6:18 pm
[...] Read it. Michael Moore is an immediate suspect. [...]
December 31, 2007 at 11:03 pm
Dr. Filler:
I have no problem with – but am agnostic about – the model of both hominid bipedalism and great ape knuckle-walking evolving from the “bipedalism” (specifically, arboreal brachiation and terrestrial bipedalism) of arboreal Miocene apes like Morotopithecus and Oreopithecus. I also accept the importance of discontinuous major developmental change in macroevolution.
The “bipedalism before knuckle walking” model (which is more to the point than “20 million year old human” or” apes evolved from humans”) may well be correct. And if you are right about that, you deserve plenty of accolades. Even if your model is wrong (and hominids evolved from knuckle-walking ancestors who evolved from “bipedal” Miocene apes), your developmental approach emphasizing spinal evolution is a significant accomplishment in the field of paleoanthropology.
However, I have a big problem with your use of the term “human” (or “humanian”) to describe these bipedal Miocene apes.
Your argument that spinal characters ought to be determinative of human status is unconvincing. You say is that “human” status should be based on body plan, yet your definition does not mention a remarkable feature of the human body plan – our greatly expanded brain relative to apes.
Putative biped Miocene apes are human? I don’t think so. In addition, I consider australopithecines to be bipedal apes. Hominids, yet apes. Only members of the genus Homo deserve to be called human based on brain, behavior, and ecology. The real transitional species between human and ape is H. habilis, not Morotopithecus.
Is Morotopithecus today’s Ramapithecus? (That is, the “earliest human” who wasn’t?) We’ll see.
December 31, 2007 at 11:36 pm
As a practicing scientist, I’d strongly recommend that you ditch the whole “let’s redefine the word ‘human’” angle and focus on your actual claim, which is a bipedal ancestor for the apes. That’s clear, and it’s clearly science. This bit about what “human” should mean makes you look like a loony, and it has nothing to do with your scientific contribution. Get famous by shaking up the science using the old guard’s terminology. Then argue for a terminology change.
January 1, 2008 at 1:16 am
In addition, I am not convinced that Morotopithecus and the rest ought to be called “bipeds” any more than so-called “eubipedal” hylobatids do. Sure, they are bipedal when on the ground – but they are primarily arboreal. (Sifaka are bipedal on the ground – should they also be described as bipeds?) With perhaps equal justification Homo sapiens could be called “quadrupedal” since we use all four limbs when swimming or climbing trees. Rather than throwing around terms like “biped” (much less “human”) we should acknowledge that brachiating hominoids have erect (or at least diagonal) posture. (That is part of what makes knuckle-walking so distinct from cercopithecoid quadrupedalism.) I think “brachioforms” is a more appropriate name for this group than “bipedal apes,” “hominiforms” or “humans.”
Lay people don’t know what you mean when they see headlines about apes evolving from humans. They see those kinds of headlines and think chimps and gorillas literally evolved from us or something like us.
January 1, 2008 at 3:01 am
A circle-the-wagons mentality has led to a rigid opposition to saltational or punctuated models of morphologic change since the 1850’s. Darwin was afraid the public would see acts of God as in Sir Richard Owen’s “serial acts of creation.” He insisted on only gradual change so the public would not get the wrong idea. Insisting on a given position to avoid the evidence but also avoid alarming the public or aiding the predatory creationists is never right if it forces scientists into models that aren’t optimal.
In “The Upright Ape” I cover in detail how we arrived at our current usage of “human” in paleoanthropology.
We do like to hide behind latin to avoid alarming the public. See Wolpoff et al in their comment in Nature (2002 – v419:581) “Sahelanthropus or Sahelpithecus?” But when Ann Gibbons – a paleoanthropologist who writes many of the news columns on paleoantrhopology for Science – wrote about the discovery of Sahelanthropus – she entitled the book “The First Human.” She’s talking about the species that may be ancestral to the chimpanzee lineage. She is following in the tradition of Don Johanson and Tim White who promoted “Lucy” in this fashion. Russell Tuttle has also covered the issue in his 2006 article “Are human beings apes?” in the Ishida et al volume on human origins.
I am specifically departing from Sir Arthur Kieth’s “Hylobatian” model because it implies an ecological scenario for our upright origins – that it derives from a lineage exploiting a niche available to a brachiating hominoid. Instead I am expressing the consequences of a morphogenetic basis for human origins. Our upright form derives from a homological discontinuity – the hominiform lumbar transverse process (LTP) is based on an arch structure – the anapophyis or styloid – and therefore carries the longissimus attachment. This is distinct from the typical catarrhine condition of a rib based LTP that does not have muscle attachments.
The box-like cross section of the human LTP and the LTP in Morotopithecus is structured (as the human trabecular pattern shows) for hindlimb supported upright posture. This is not about brachiation, it’s about a morphogenetic origin of a bipedal lineage or clade I term hominiforms. We do not know that they were arboreal and it doesn’t matter if some were. We can’t ignore morphological evidence just because we haven’t thought of a convincing ecological just-so-story to justify it.
The term “proto-human” reflects what I call an “Aristotelian logical error.” Obviously, our ancestral species are not just like us so they can’t fit into our category. This is further aggravated by insisting that australopithecines are bipedal apes and that the expanded brain of Homo habilis is the first feature usable as the determinant of “humanity.”
Terry Deacon (The Symbolic Species) is focused on the onset of symbolic thought as the basis for linguistic communication as the determinant of humanity. This probably excludes Homo habilis. One of the comments above also suggests that Homo erectus needs to be viewed as an ape as well.
The founding hominiform lineage may have been a terrestrial upright biped that was not an arm swinging brachiator. If you want the whole symbolic linguistic package to define humanity vs animality, you may end up including only Homo sapiens sapiens – with language, art etc. If we accept Sherwood Washburn’s premise – that has been the basis of most scientific antrhopological models since the 1950’s – then it is primary bipedalism that distinguishes the human animal from the ape.
January 1, 2008 at 9:27 am
Evolution doesn’t say we are the pinacle result of evolution, or that they are an end to evolution.
January 1, 2008 at 10:24 am
I am sure that you have heard the oft quoted wife of a London aristocrat, upon hearing Darwin’s claim that man descended from apes, reponded, “My dear, let us hope that it is not true, but if it is, let us pray that it may not become widely known.” I appreciate the fact that you have noted above that this same “circle-the-wagons” mentality is prevalent in the scientitific community as well. I would contend that another clear short-coming of the scientific community is the unadmitted drive of today’s scientists to be as provocative as possible.
The question is not about suppressing the facts or avoiding alarming the public but rather how to pump up the shock-factor of whatever theory or premise is being exposd. Certainly, to state that “Evidence exists for a bepidal ancestor to apes” does not quite have the same shock factor as a stating “Apes evolved from Humans”. The insinuation that you are only being scientifically honest by not allowing your theory to be influenced by whether or not it “alarms” anyone seems to me to be disingenuous. Search your motives. IS your reason for using “human” really based on current accepted usage of the term in the scientific community or is it your attempt to back into an answer that makes for the best book title?
January 1, 2008 at 10:39 am
Paleoanthropology has been poorly served by a drive to lay claim to the earliest “human.” Henry Fairfield Osborn’s “pithecophobia” that led to his endorsement of Eoanthropus. Louis Leakey’s dubious inclusion of habilis in Homo. Pilbeam’s Ramapithecus. Johanson’s characterization of Lucy and claims for her implications (scientists had already long known that australopithecines were cranially apelike and fully bipedal. In addition, Zihlman was right about Lucy.) Somehow, paleoanthropologists keep identifying direct human ancestors – while banishing discoveries made by colleagues to side branches. In addition, these formulations have biased artistic reconstructions, resulting in pre-erectus hominds that are implausibly human-looking. (This tendency has been curbed since the seventies.)
True, there is a tradition of somewhat whimsically calling humans “naked ape” or “third chimpanzee,” and deeming every putative direct human ancestor that likely walked on its hind legs “man” or “human.
What you have demonstrated is that Sherwood Washburn’s premise was wrong, and bipedalism alone is not what distinguishes the uniquely human lineage – the lineage that includes only us and no other living species – from apes. The spinal innovation criterion of “humanity” is as arbitrary as any other discontinuous change that occurred in humanity’s entire evolutionary lineage prior to our split with Pan. And if we had evolved from knuckle-walking ancestors, would that make us pongids? Or hylobatids, if Keith were correct?
At the very least, only forms that postdate the Pan-Homo split should be included in even a colloquial “human kindred,” bipedal or not. (I know, early hybrization complicates the picture a bit.) If Morotopithecus had somehow survived to the present and we had always known the species, it would be kept in zoos and used in entertainment, not regarded as “human” – not even by biological anthropologists – just because it walked on its hind legs. Even TV and movie apes do that.
So we have one solid criterion of even an overly inclusive “human kindred”: our side of the Pan-Homo split. What about “human”? Do we need to identify the origin of language, or even less justifiably, define humanity based on the Upper Paleolithic revolution? Not at all. It can be done on behavioral ecological grounds, a suite of features that distinguishes our unique clade. Regularizing tool-making, long range travel, cooking, hunting of large prey, morphological-life history indicators of humanlike sociality (e.g. reduced dimorphism). That disqualifies the apelike habilis, who should have been banished from Homo long ago. And soon, the developmental-genetic basis of changes in the brain will be better understood, including discontinuous events, and these genetic changes will be correlated with behavioral ecological features. (Also, I have also long suspected – and accumulating evidence vindicates – that the cognitive differences between Homo sapiens sapiens and Neandertals and other archaics has been wildly overestimated.)
January 1, 2008 at 7:30 pm
Sherwood Washburn’s premise about the definition of humanity in bipedalism has been a core tenet of paleoanthropology for more than 50 years. When I first realized the implications of the Moroto vertebra in the 1980’s I was able to correspond with Washburn and he accepted that he may have underplayed the importance of bipedalism before the chimp-human split.
As I point out in “The Upright Ape,” Washburn’s formulation was a defensive response to Irven DeVore’s PhD thesis. DeVore and Tuttle – both of whom were Washburn’s students and both of whom were my advisors – understood the origin of this definition of humanity and looked to direct me to focus on the spine to try to test the validity of Washburn’s hypothesis. This is also why David Pilbeam put the Moroto vertebra in my hand and asked me to analyze it in the first place.
The definition of humanity is not a shock factor claim – it is one of the the core subjects of paleoanthropology. Because the outcome of this three decade project has the result of overturning Washburn’s hypothesis, it is appropriate to address the issue head on.
It is not the case – as Colugo suggests – that the spine characters are equivalent to any other we may choose. This is because the impact of homeotic genetics shows that early changes in the principal segmental morphogenes in the Hox and Pax families are key to much of body plan evolution in the mammals. Also, Colugo may not be aware that the SNT change described in the original post and in the PLoS One article is part of a suite of changes that appear to be linked to the Uncx4.1 gene. In the undulated mouse mutant – a single gene change pushes the horizontal septum dorsad in the spine, but also results in an antero-posteriorly flattened chest and repositioning of the scapulae posteriorly. Pax and Hox gene changes are often massively pleiotropic – they affect many aspects of morphology at once. In this case, a number of features of hominiforms which we have attributed to gradual independent ecological pressures may have all change at once on a morphogenetic basis.
This is what I mean by a morphogenetic basis of human origins.
This ties in with the issues raised in the comments about limiting the term “human” to those species following the chimp-human split which meet certain intellectual criteria. The Hennigian paradigm is that when a small founder population splits off to found a new species then the parent species is considered immediately extinct and there are now two new daughter species. This is point when a post-split human lineage could be considered to have started.
I cover this issue of species concept in The Upright Ape in some detail. Ernst Mayr thought this was an unbiological abomination. The parent species would look the same and have effectively the same gene pool when a new founder species split off. He objected to calling the main lineage a new species an the parent species extinct since the parent species and at least one of the daughter species were exactly the same.
This is my point about having a human ancestor for the chimpanzees and possibly other modern ape lineages. If the pre-split main species and the post-split main species are identical genetically in every way, it greatly offends Mayr’s view to consider the post-split creatures humans and the pre-split creatures apes. This really makes apes and humans the same.
I have suggested that most of the major body plan innovations we see at 7 million years ago had appeared in Morotopithecus by 21 million years ago as a result of a major morphogenetic event that generated the primitive hominiform body plan – an upright bipedal species with five or six lumbar vertebrae.
I then propose a string of descendant species in which there was typically a relatively primitive generalized hominiform body type – that is the human body type. The first equally profound change to strike this chain of species was the brain size increase we first see clearly in Homo habilis.
To insist that there can only be one kind of human species and it has to be pretty much just the kind of human we are – simply is a way of trying to restrict the term “human” to just our current species of Homo sapiens. This position – that australopithecines are not proto-humans because of their small brain size – could have been proposed by Washburn. It is a long time since Dart’s original discoveries that showed australopithecines had chimp-like brains. There is nothing we know now that makes it any more appealing to make Homo habilis an ape.
However, the new evidence inexorably shows that the common ancestor of the chimp and human lineages appeared to have a body plan more similar to our human body plan than to a chimp’s body plan.
This is why I have identified the body plan as identifying the human animal and reccomended adjectives to define and distinguish the various subtypes. I have also provided a collection of synapomorphies – shared derived features that provide a usable morphologic definition of a human. A paleontologist who has found a totally complete skeleton of an eight million year old hominiform or a three million year old hominiform has to be able to tell whether the species was ape or human and only a morphological definition can accomplish that.
Aaron Filler
January 1, 2008 at 8:15 pm
1) There are a number of homeotic transformations with pleiotropic effects in our evolutionary lineage, as far back as one wants to go. That change that you discuss is not arbitrary in terms of orthograde hominoids. But it is in terms of identifying human status. It is too inclusive because it is too primitive. A better character – because it more derived and hence more exclusive – would be erectus (or even, arguably, habilis) brain expansion. (By the way, why no mention of Richard Goldschmidt – who is useful, in his proper place.)
2) What is Dr. MacLatchy’s current assessment of the locomotor behavior of Morotopithecus? Has she changed her mind?
My quarrel is really with your use of the word “human.” But as I said, your analysis constitutes a significant contribution whatever the sequence of locomotory evolution turns out to be.
January 2, 2008 at 12:26 am
Don’t you see what you have done? You have dethroned bipedalism in paleoanthropology*. For a long time a major question in human evolution was whether bipedalism or encephalization was the more critical evolutionary change that enabled the evolution of humanity. For decades that question appeared to be settled with the discovery, description, and acceptance of Australopithecines. Since you have argued that our lineage’s bipedalism long predates the chimp-human split, then it can no longer be the premier distinguishing characteristic separating humans from apes. And determining which features make humans different from apes and when and how these evolved was a major project of human evolutionary biology. If bipedalism is a primitive feature, it is like taillessness, Y-5 molars, or any other primitive feature that fails to distinguish us from apes. (It’s just a feature that extant great apes happened to lose.) The australopithecines are more clearly seen as yet another African ape radiation, one that happens to postdate the Pan-Homo split. Citing decades-old tradition (within a much longer history of human evolutionary research) is not sufficient for the retention of bipedalism as the central distinguishing feature.
Bipedalism is dethroned. That leaves encephalization. This is the aspect of the human bauplan which is most critical to our evolutionary story.
*That is, if you are correct.
January 2, 2008 at 4:01 am
‘Bipedalism’ is not precise enough a term. Birds are also ‘bipeds’, as was Tyrannosaurus Rex. Gibbon bipedalism is not the same thing as human bipedalism.
Human ‘bipedalism’ is of a very special type, characterized by the projection of all the gravitation centers of the body parts into a single frontal plane. This special condition I call ‘uprightness’. We should think of bipedalism, not as a single Merkmal, but as an evolutionary process that proceeds with jerks, and reaches completion in humans.
Evolution in primates seems directed towards uprightness. Monkeys already bear more of their weight on their hindlimbs, as compared with a dog or an elephant, for instance. Dr. Filler identified an important intermediate stage in this process. Uprightness with exception of the skull is present in Homo erectus or Homo neanderthalensis. Only Homo sapiens s. has developed full uprightness, including equilibrium of the head.
January 2, 2008 at 5:52 am
[...] suggestions for this issue would be Dr. Filler’s discussion on human ancestry for apes and Remote Central’s post on the European creationist theme [...]
January 2, 2008 at 6:16 am
Colugo, I definitely think your interpretation has merit, though as an archaeologist and not a physical anthropologist, I come from a background more willing to think of Australopithecines as essentially apes.
January 2, 2008 at 7:36 am
A very sensationalist headline, seemingly designed to bait anti-evolution fundamentalists.
But I guess “Bipedal Ape Ancestors Evolved Into Modern-Day Quadrupedal Apes?” doesn’t have quite the same zing…
January 2, 2008 at 7:48 am
[...] Source : Anthropology.net. [...]
January 2, 2008 at 10:30 am
In “The Upright Ape” I do look into the anatomy, embryology, physiology and motor programs that underly a variety of types of bipedal locomotion in animals including dinosaurs, birds, running lizards and even some insects. In defining humans, it is precisely a matter of the role of bipedalism in hominoids and not bipedalism in general.
Also, in the Neurosurgical Focus paper (with a link at the beginning of this blog post) I cover the various anatomical modifications of anatomy that optimizes bipedalism in australopithecines and various species of the genus Homo. The Hominiform Progression video (see link above) shows hylobatid bipedalism and helps provide a feel for some versions alternative to our own.
There are various different ways of aligning centers of gravity, but there really is no option for “off balance” forward stooped bipedalism. I see patients referred to me for help who have had incompetently performed spinal fusions so that they can’t stand in a fully balanced vertical upright position and it is incredibly painful – the spinal muscles are in constant struggle and any perturbation caused by lifting or turning is very difficult to accomodate. This is not just a matter of pathology in modern humans – I don’t think you can have a functioning primary mode of locomotion that is continually off balance and demanding intense muscle activity to maintain uprightness. I therefore consider any upright bipedal hominoid to have had a well balanced bipedalism well suited to its usual locomotion.
One of the images in the post above shows a gibbon walking up a vine – something that 99.999% of humans certainly can’t do. From the gibbon’s point of view, humans are handicapped by our fused-in first toe and are unable to walk bipedally in many natural substrates such as narrow branches and vines.
The hominiform synapomorphies that underly our bipedalism are not found in the extinct proconsulid apes. They had tail loss and the Y-5 molar, but had more monkey-like quadrupedal style spine and limbs (see the cladogram in the post). Therefore this is not just another distant primitive feature of all hominoids.
I agree that my conclusions further decouple the origin of our bipedalism from the origin of our human intellectual capacity. It is now even more clear that these two aspects of human existence are not directly intertwined in evolution, but this could be seen from what we have known for decades from australopithecines.
However, I would not “dethrown” bipedalism. Primary bipedalism is extremely rare in mammals or even in the entire synapsid radiation over more than 300 million years.
We have tended to view the australopithecines as being transitional forms along the direct short path from ape existence to fully human existence – carrying, throwing, and complexly thinking. Instead, I would focus on understanding “pre-sapient” human species on their own terms. What is the impact of the bipedal body form on competition with meta-bipedal apes and quadrupedal monkeys? In “The Upright Ape” I pick up Gould’s theme of hierarchical evolution to emphasize that not all evolution relates to competition between individuals in an interbreeding population. Speciation and body plan innovation produces new versions of an animal – species and even higher order groups (e.g. mammals vs dinosaurs) can compete with each other based on their unique biologies.
What this results in is forcing the scientist to consider that for the vast majority of existence of the human body plan, it has been a very successful body plan. This is without the special intellectual capabilities shown by humans from the genus Homo. For 19 million years there have been successful species of “pre-sapient” human hominiforms (terrestrial primary bipeds) which have spread from continent to continent. Only in the last two million years has brain size expansion resulted in “sapient human species” able to eradicate the “pre-sapient” human species of which none survive.
There is no definite answer. However, I feel that by focusing excessively on our intelligence, speech and culture, we tend to miss some of the aspects of our upright bipedal body plan that are also essential to our humanity. For this reason, I would not discard the “non-sapient” human species. I would include as many of them as there are from Morotopithecus onwards as humans, and refocus our anthropology – as Lieberman and other have done recently – to look at issues like the energetics of long distance walking and other aspects of hominiform bipedality – to better understand who we are.
Aaron Filler
January 2, 2008 at 1:01 pm
Points well taken, Dr. Filler. I broadly agree with you about hierarchical selection, homeotic change, and the bauplan approach.
Let me suggest a new meme: Replace the term “human” to describe the orthograde hominoids (AKA modern apes, eu- and metabipeds, advanced hominoids) that emerged about 20 million years ago with the term “orthoapes” and reserve “human” for the group with greatly increased brain size (ergaster/erectus, archaics, modern sapiens). Orthoapes. Rolls off the tongue, doesn’t it?
January 2, 2008 at 9:37 pm
I find it hard to believe that someone would actually argue that the term “human” should be applied simply based on the fact that a hominoid mammal walked on two legs, let alone upright. Regardless of whether or not the term is defensible from an anthropological or physiological stand-point or not. If your neighbor broke into your house, killed or incapacitated you with blows, and then dragged your daughter to his own place to forcibly mate with her, most rationale people would consider such a species “inhuman”? And yet this activity is common, natural and expected of the same ape species which Dr. Filler proposes to term “human”. I think the term “human” deserves a bit more dignity than that.
January 3, 2008 at 3:35 am
truthvitamin – with all due respect, are you describing known behavior of some extinct species? There certainly have been modern humans who have committed crimes such as you describe, but that doesn’t allow us to deny the term “human” to our own species. I think what you mean is humane and inhumane behavior. As I’m sure you know many humans have committed many horrible crimes. Sometimes, entire nations engage in publicly supported genocide, etc.
It would be nice to have a way to classify the ethical level of a hominiform species, but your definition would seem to exclude Homo sapiens sapiens as well. There has always been a mindset that compares the noble god fearing, devout caring church going human to the savage animals. This notion has a powerful effect and helps drive the creationists revulsion with the idea that humans could be related to apes. However, apes also display noble and sensitive behavior and modern humans can display vicious behavior. That is we have police forces and a millions of people incarcerated for crimes in this country. It is interesting to reflect on this, but I don’t think it provides a way to determine how the word human can be used in describing species.
If gibbons and siamangs proved to be wonderfully monogamous and totally non-violent towards each other, would you call them human on that basis?
January 3, 2008 at 11:07 am
Dr. Filler – You seem to be arguing from the exception and not the rule. To say that a species may, from time to time ,exhibit a particular behavior does not qualify it as being exemplary of that behavior as a general rule.
While you are trying to justify your own personal anthropological derivation of the term “human” as it relates to a species, you cannot disregard how that term will be viewed and perceived by the reading public. I am only commenting on the generally accepted semantics of the term, be it in science or the general public. My point was simply that the correct use of the term “human” can be best derived from looking at the use of its opposite, in this case, “inhuman”. Whether that behavior is by an ape or a human, it still carries the same meaning. To my knowledge, at least, no one uses the term “inhuman” to describe NOT walking upright on two legs. (N.B. the terms “inhuman” and “inhumane” do have slightly different connotations)
With all due respect, the title of your entry “A Human ancestor to the Ape” seems to me to be at best misleading and at worst insulting. I feel as though use of the term “human” deserves more dignity than that and to be quite frank, your commendable research and noteworthy findings deserve more dignity than that. Based on your further elaboration on this issue, it seems clear that your true intent was not to present a learned display of the facts but rather to simply further fan the flames of “the creationists’ revulsion with the idea that humans could be related to apes”. In the latter, you seem to have succeeded.
January 3, 2008 at 8:34 pm
Truevitamin – you may not have read through the replies above. In biological anthropology, the most widely accepted demarcation of proto-human vs ape derives from Sherwood Washburn’s position that after the chimp-human split, bipedalism developed in the proto-human lineage. He relied on bipedalism to make it possible to assign fossils to the human lineage vs the chimp lineage. If bipedalism predates the chimp-human split, then that definition needs to be reassessed and that is what I’m doing. Particularly as it affects Sahelanthropus – a species already categorized in the proto-human lineage on conventional criteria appears to also be ancestral to chimps. This is why it appears that there may be a human ancestor for at least some of the apes.
I presume that the violent behavior you described refers to chimpanzees. That doesn’t help answer the question of whether to call Australopithecus or even Homo habilis apes or early/proto humans. It’s not about insults its about classification and morphology. I also make the point above that you can’t test hypotheses and make decisions in science based on what effect it may or may not have on creationists. If a creationist believes that all species were created in their current form about 6,000 years ago, none of your concerns about dignity really matter.
If you believe Hobbes – then human life was nasty brutish and short before government established the principal of monopoloy of force. If you believe Rousseau then man was “good” in a state of nature but was corrupted by society. You can look at the Yanomamo to support Hobbes or look at the Kung to support Rousseau. We’ll never know which met your “majority ethical” criteria in which pre-Homo sapiens sapiens species.
At one extreme we have the Osama bin Laden’s Wahabi sect who believe that all others are so ethically inferior that God will rejoice in the brutal slaughter of all non-Wahabis because they are more or less sub-human. They are all about optimum human dignity.
I think these are certainly valid issues, but I can’t accept your argument that only “good” modern members of Homo sapiens sapiens can be proven to have sufficient “dignity” to be considered human.
As books like “The Last Human” and “The First Human” show, it certainly is not my idea to include australopithecines and Homo habilis as (adjectivized) human species. I do believe that there is a human body plan and that it has a lot to do with being human and that this type of creature has a long history – back to Morotopithecus. It is important to understand that we retain many of the longstanding or primitive anatomical features that have been abandoned or evolved away from by various ape lineages. Increased brain size and symbol based language are very important to our species, but it does appear to be plausible to argue that the “human” type of body plan does include a wider range of species than just our own.
Aaron Filler
January 3, 2008 at 9:15 pm
I read some passages from The Upright Ape. Theoretically the book is cutting edge, like the work of Terrence Deacon. The discussion of cellular selection is excellent.
Questions:
1) Are living gibbon and siamang species human?
2) Would Washburn and his peers have made bipedalism the primary criterion of human status had they not believed that bipedalism evolved (or re-evolved) after the Pan-Homo split, rather than being the primitive condition of modern hominoids?
January 11, 2008 at 9:52 pm
I agree with the opposition with this usage of “human”. I think that the problem of gibbons and orangutans was well pointed. But perhaps some people would agree with a more inclusive usage of “human” that would embrace most of the apes (I think of Goodman and perhaps Singer). But perhaps chimps and gorillas could also be considered as “secondary inhumane”, like some dinosaurs are hypothesised by some to have been a lineage of birds in which evolved secondary flightlessness.
While I don’t really care that much, for myself, I think that worth some concern the mental image the term creates for some part of the lay public, as was pointed by some people. And… specific segments of crackpottery, like creationists who may think that it would support the idea that other apes descend from Homo sapiens from the ark, and this other thing up there with the guy who argues that humans evolved in the water from some sort of buoyant big-brained pikaia and are the common ancestors of all terrestrial vertebrates… I have the gut feeling that a different phrasing like “gorillas and chimps evolved from bipeds” or something like that would be less prone to spark this sort of things. But maybe wouldn’t have much difference.
January 24, 2008 at 1:25 pm
[...] of a contentious statement. It is reminiscent the curve ball Aaron Filler’s threw us in his human ancestor for the apes hypothesis, because the current understanding is based upon fish with fins gave rose to amphibians [...]
February 26, 2008 at 3:40 am
I have believed now for some time (10 years or so) that indeed apes are the descendants of man. I’m not a p.h.d or anything like that but i am a student of the mysteries. Your theory is certainly interesting to me. I read Madam Blavatsky’s anthropogenesis and cosmogenesis about 10 years ago and have since researched many of her ideas (I am not a theosophist but I am a student of ancient religion and philosophy). In fact I must say the concept she put forth , which is the topic under discussion here, is actually an acceptable if not necessary conclusion in light of many ancient mystery traditions including that of the judeo-christian religions. In my research I have come the the conclusion that the bible in specific refers to a race of man that lived on the earth and founded technologically superior civilizations millions if not billions of years ago. This early race of man was responsible for administering the evolutionary process of all life on earth throughout the ages. Of course they most likely were not in the form that mankind appears now in their earliest state of terrestrial being, but gradually perfected there form until at last reaching the state that mankind appears in even to this day. I know these ideas are considered pseudo-science by the common standard of our present era but i think if you were to take the actual scientific data available to us now and correlate it with the various mythological histories of the different cultures around the world you world begin to notice a certain agreement between the two fields of study. Personally I think your on the right track… I hope the fact that I am a mystic and am in agreement with your observations doesn’t lend to the devaluing of your good reputation, but I’m happy to see someone looking a little deeper than the surface to find truth regardless of the popular opinion.
March 7, 2008 at 3:24 pm
“This suggestion definitely has the quality of blasphemy against religious doctrine.”, you said. But evolution does not completely go against one religion and that is Sikhism, world’s 5th largest religion.
April 9, 2008 at 2:02 am
Would like to hear more from Jos Verhulst on the animals center of gravity and how our human C of G has become directly in a vertical line. Which was first – vertical or horizontal? Etc.
May 29, 2008 at 8:58 am
I’ve read the artcle and most of the comments and it’s very interesting.
Filler has demonstrated that the term ‘human’ applied to our bipedal ancestors is not necessarily wrong. I still find it, however, at least confusing, and that cannot help the science divulgation.
I dont agree with Colugo’s ‘orthoape’ cause I speak spanish, and the spanish translation ‘ortosimio’ doesn’t sounds well at all. But more important, I think Filler wouldn’t agree in taking that name cause it refers to the ‘apes’ and if I understood something, that’s just what we don’t want, cause apes descended from those ‘AKA modern (apes), eu- and metabipeds, advanced hominoids’. I think it’s better to refer to humans, just dont use ‘human’. It could be, for example just ‘homids’ (spanish: ‘hómido’, same rooth, different descinence)
July 17, 2008 at 3:32 am
What I really enjoy about Filler’s recent work is not that I’m necessarily won over by his arguments but rather the challenging nature of the ideas. Morotopithecus may or may not have been our ancestor (though I’m certainly swayed to notion that it was a habitual biped) but what I find puzzling is the resistance to the notion that we may have evolved from a line of apes which had been upright for 20 million years.
As the post-cranial fossil evidence from beyond 4 million years is sketchy at best there is no reason yet to fight off Filler’s scenarios. So what if they were upright all along? Are we trying to discover our true ancestry or just attempting to make sure what we find adheres to long standing ideas about our ancestors?
When, and if, the definitive fossils from the divergence of chimps and apes are found they’ll speak for themselves. No need to get up in arms and take sides over an issue which simply is not clear at this point.
August 3, 2008 at 10:50 pm
where does human intelligent comes from. why is it so miraculous.
How did a bunch of cells (brain) capable to understand evolution (million years of learning process at molecular level) in a shorter time?.
Or is it not to ‘understanding’, is it more to ‘memorising’?
October 13, 2008 at 12:15 am
Read the book and the papers posted on the site. It is definately a positive step in understanding our ancestry. Dr. Filler, excellent work. Now if eveyone can overcome their Pithecophobia they will recognize that it is the most likely sequence of events possible. But I do agree that Human in the title is misleading. How about Humanoid?
June 2, 2009 at 11:04 am
[...] in doing so… But given that one of Anthropology.net’s most popular posts discussed an origin of humans for apes and that I’ve researched a bit about Eurasia hominoids last year, I think you should be [...]
June 4, 2009 at 12:17 pm
“But I do agree that Human in the title is misleading. How about Humanoid?”
Perfect!
In fact, all the apes are already humanoids. Hominoidea (the clade containing apes and humans) means “humanoid”.
August 13, 2009 at 5:39 am
[...] Thorpe of Birmingham (see Thorpe et al. 2007) and Aaron Filler of Harvard (see, for example, his post on Anthropology.net, A Human Ancestor for the Apes?, or his book, The Upright Ape: A New Origin of the Species [...]