Is Lucy a chimp ancestor?

A reader asks whether Australopithecines were actually the ancestors of another ape lineage, rather than our own.


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Today is Wednesday, which means I answer a question from you lovely readers. If you have a question about human evolution, you can get in touch through email, twitter or facebook. You could even just leave a comment on this post. I’m so easy to contact you have no excuse!

Self-plugging over, let’s get on with it. Today we’re dealing with one from Art, who wonders whether or not Australopithecus (a fossil hominin from 2 – 4 million years ago) is actually an ancestor of gorillas or chimps, rather than humans. He writes

One or two popular writers (Diamond, Dawkins) have suggested the possibility that bipedal Australopithecines may be ancestors of the Chimpanzee and Gorilla. Do you know of any evidence that would rule this out?  Do you know of any solid evidence that supports it?

Australopithecine and chimp skulls, showing just some of the similarities between the two

Australopithecine and chimp skulls, showing some of the similarities between the two

It is certainly true that the Australopiths possessed many ape-like characteristics more similar to chimps and gorillas than humans. These include small brains, prognathic faces, brow ridges, arms and hands adapted for climbing and many more. And yet most palaeoanthropologists still argue that they are more closely related to humans rather than to these other apes they resemble.

This is because evolutionary biology doesn’t identify relationship by comparing the raw number of similarities between a species. Rather, they look for synapomorphies. These are traits which are unique to one particular lineage, having evolved since they diverged from others, so can be used to define it. Thus if you find them in a fossil there’s a very good chance your looking at an ancient member of that lineage.

Many of the similarities between Australopithecus and the non-human apes aren’t synapomorphies. For example, both gorillas and chimps have a small brain, so this can’t be used to define either. As such, the fact Australopithecus has a small brain isn’t evidence it was an ancestor of gorillas or chimps.

Conversely, many of the similarities Australopithecus shares with modern humans are unique to our lineage, indicating that Australopithecus is part of it. Things like habitual bipedalism, use of stone tools and many boring things relating to the shape and size of their various bones are all traits which define the human lineage and are present in Australopiths. These synapomorphies mean that we can say with confidence that Australopithecus is a member of the human family.

Some of the human synapomorphies peresent in Australopithecus

Some of the human synapomorphies peresent in Australopithecus

Of course, the fact that share so many similarities with the other apes is still interesting. It shows that Australopithecus is an archaic member of the human family, perhaps an ancestor of later species. It sheds light on how the modern human form evolved from a more ape-like one and tells us what our ancestors were like millions of years ago.

But it doesn’t mean they aren’t part of our family.

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32 thoughts on “Is Lucy a chimp ancestor?”

  1. ThQ says:

    Something that particularly struck me lately is that there are species much older than any Australopithecines that are clearly less prognate than they are. The most prominent examples I can think of are Kenyanthropus Platiops and Sahelanthropus Tchadensis. Since furthermore Sahelanthropus is very close to the human chimpanzee divergence and since chimps are prognate, I wondered if this implied: either 1) that Australopithecines developed prognatism over time (perhaps under the same evolutionary pressure as the ancestors of chimps) and then their descendents lost it (after all we are not prognates); or 2) that Australopithecines are not part of the human lineage but part of that of chimps, although not necessarily an ancestor of chimps. Food for thought: we haven’t find ancestors of chimps and gorillas. Is it because we are not looking for them where they are or because we put in the human lineage some fossils that do not belong there ?

    1. Adam Benton says:

      For the reasons stated in this post, I don’t think the discovery of these flat faced fossils is enough to suggest Australopithecus is not part of the human family. At best it would mean Australopiths represent an archaic offshoot.

      But I think even saying that is going a bit far since we’ve only found one skull from each of these non-prognathic species. We know many other hominins have considerable prognathic variation (including Australopiths). We can only make evolutionary inferences from Sahel et al. if the specimens we found represent the norm, and we can’t know that from one fossil.

      There’s also the fact that both specimens are both fragmented and misshapen. Whilst we can try to compensate for that (and I think we do a fairly good job) I think enough doubt remains for us to require a less deformed specimen before making such a major change to our family tree.

      Finally, we also have to take into account that so few early flat faced fossils have been found. Given all the effort invested in digging up our ancestors and the hundreds of fossils uncovered, I think we should’ve found more than 2 skulls, millions of years apart, if there was a lineage of non-prognathic hominins.

      1. ThQ says:

        Personally, I agree with you that Australopithecines are not ancestors (not necessarily direct) of chimps but I still find it strange that we find these flat faced fossils that are so much older than Australopithecines. About the fact that we have not found many such fossils, this should really not be an argument. The discovery of Sahelanthropus and Barelghazali show that we have not been looking for old fossil in all places where they show up. As far as I can tell, the civil war in Tchad was responsible (in part) for this, together with the now dead east-side story hypothesis. Also how come we find fossils in northern central africa and south-africa with nothing in central africa ? Clearly this has much more to do with fossil conservation, on the ground politics and current mindset than anything else. There may be much much more flat faced species waiting out there in Tchad or Central African Republic….

        1. Adam Benton says:

          The flat faced specimens certainly are fascinating, and I look forward to any future discoveries. Apparently they found some postcranials of Sahelanthropus, although it hasn’t been published for some reason.

          Obviously the location of Sahelanthropus suggests there are many more fossils yet to be found, but I still think we should’ve found more than 2 by now. Perhaps not many more, but still more than that.

        2. ThQ says:

          It seems to me that supporting the view that some Australopithecines are our *direct* ancestors imply that neither Sahelanthropus nor K. Platyops nor any other old flat faced species that could be discovered in the future could be our *direct* ancestor. Unless of course one is willing to say that pronounced prognatism appeared and disappeared several times in our lineage. On the contrary it seems to me that since chimps are prognats and since Sahelanthropus (being close to the divergence) is not, then prognatism could be a derived character which appeared in both the lineage of chimps (after the divergence) and some lineages of the human familly. I mean pronounced prognatism would be an homoplasy. Then it would seem that more prognat Australopithecines are not our *direct* ancestors.

          This may seem widely hypothetical but see what happened with regard to bipedalism: originally it was thought to be a derived character. But Brunet argues that Sahelanthropus was biped and Ardipithecus certainly was too, so as far as I know, bipedalism is now more thought of as an ancestral character than a derived one. As such, the chimps’ and gorillas’ knuckle walking is derived, another example of homoplasy. Looking back at this, it could give some credence to the hypothesis that “flat-facedness” is ancestral.

        3. Adam Benton says:

          But there are already many who doubt whether Sahelanthropus is even a hominin, let alone a direct ancestor. Whilst their arguments don’t convince me that Sahelanthropus is not part of our family, the make enough good points that I am willing to accept that it may well not be a direct ancestor.

          Then there are those who think that Kenyanthropus is a deformed Australopithecine (as in, taphonomically deformed). I haven’t read their arguments as much so can’t say if they’ve got a point, but again there is some doubt there.

          Given all of this, the idea that the early flat faced species are part of a human branch that ultimately went extinct doesn’t seem especially far fetched. But, like I said, it would be nice to have more specimens before making any sweeping statements about our evolution

        4. ThQ says:

          And Orrorin too was bipedal. Quoting wikipedia on this : “Its discovery was an argument against the hypothesis that australopithecines are human ancestors, as much as it still remains the most prevalent hypothesis of human evolution as of 2012” there is a nice reading in reference for this: look here : http://books.google.com/books?id=PrJ1lmjMakoC&pg=PA116

        5. ThQ says:

          Note, I do not think Sahelanthropus was our direct ancestor (nor Orrorin or Ardipithecus etc.), only I make the assumption that, being close to the divergence, Sahelanthropus might be physically similar to our direct ancestor who lived at the same time. I realize this is a big assumption. In any case, without making sweeping statements, I believe we can still reasonably suspect that there might have existed a line of Australopithecines (or closely related), living in central africa from 7 Ma to around 3 Ma, with relatively flat faces and which are closer to us than the currently known, more prognates, Australopithecines.

        6. Adam Benton says:

          What you say about Sahelanthropus is pretty much true for every species we’ve found (and phrased much better than I’ve been able to in the past). Identifying if these species are direct ancestors is next to impossible, we can only use them to try and infer what our ancestors looked like. I think that’s a perfectly valid approach, and more productive than spending hours agonising over whether Australopithecuis afarensis or Australopitehcus africanus was actually our ancestor.

          I expect we’ll find more fossils in Central Africa. Their relation to us and their flat faces are more up in the air. After all, Kenyanthropus is from East Africa, a region riddled with prognathic species but is flat faced. Finding one flat faced species in Central Africa doesn’t really tell us what the norm is.

      2. dr jay says:

        As quoted from your text above:
        “Things like habitual bipedalism, use of stone tools and many boring things relating to the shape and size of their various bones are all traits which define the human lineage and are present in Australopiths.”

        THERE IS NO EVIDENCE ‘Australopiths’ use stone tool.
        ALL THE EVIDENCE INDICATES ‘Australopiths’ ARE NOT habitual bipeds! READ THE RELEVANT LITERATURE! THERE ARE NO CHARACTERS THAT DEFINE THE HUMAN LINEAGE(autapomorphies) that are present in “AUSTRALOPITHS’!
        PLEASE LIST THE BORING THINGS RELATED TO SHAPE AND SIZE. AS IT IS ALL YOU HAVE WRITTEN IS PARROTING WHAT YOU HAVE READ. IN FACT THE GROUP you refer to ‘Austrlopiths’ probably also contain the ancestors of African apes.

        Don’t Bullshit the masses with facts you never checked up on, To do so makes science to be like religion. Science is not based on faith and taking the written word as testament, but on each of us being able to verify these observations for ourselves.

        1. Adam Benton says:

          The evidence for Australopiths using tools is not definitive for the moment; but that’s part of what it makes it so interesting. Almost any outcome to this research would be interesting. Are there members of Homo living earlier than we thought? Is stone tool technology not as advanced as we thought? etc.

          As for Australopith bipedalism, there is volumes of evidence for it. From the angle of the foramen magnum, increasing robust metatarsals with an adducted hallux, the presence of a gene valgum, lumbar lodosis in some species and sharpes fibres in others. These are some of the synapomorphies I’m most familiar with, but there’s also changes to tooth size and enamel thickness making them more similar to modern humans, decreasing sexual dimorphism, changes to prognathism and the shape of dental arches and much more. Some of which are in the picture in my post, so please read what I say before complaining.

          A good summary of all this can be found in “‘‘Lucy’’ Redux: A Review of Research on Australopithecus afarensis”; which can be found freely availible at some places.

    2. dr jay says:

      As quoted from Adam Benton text above:
      “Things like habitual bipedalism, use of stone tools and many boring things relating to the shape and size of their various bones are all traits which define the human lineage and are present in Australopiths.”

      THERE IS NO EVIDENCE ‘Australopiths’ use stone tool.
      ALL THE EVIDENCE INDICATES ‘Australopiths’ ARE NOT habitual bipeds! READ THE RELEVANT LITERATURE! THERE ARE NO CHARACTERS THAT DEFINE THE HUMAN LINEAGE(autapomorphies) that are present in “AUSTRALOPITHS’!
      PLEASE LIST THE BORING THINGS RELATED TO SHAPE AND SIZE. AS IT IS ALL YOU HAVE WRITTEN IS PARROTING WHAT YOU HAVE READ. IN FACT THE GROUP you refer to ‘Austrlopiths’ probably also contain the ancestors of African apes.

      Don’t Bullshit the masses with facts you never checked up on, To do so makes science to be like religion. Science is not based on faith and taking the written word as testament, but on each of us being able to verify these observations for ourselves.

  2. Ashley Haworth-roberts says:

    Off-topic but Liverpool are doing well in University Challenge so far – under-grads wiping the floor with post-grads from Keele.

  3. andre salzmann says:

    Does Sediba not suggest a “link” between Australopithecus and “early humans” ? Do we know or think that there were three lines of Australopithecus ? Years ago they were named Robustus ( big molars) Boisia ( more modern0 and I think Paranthopus ? One does not seem to come across these names anymore.
    If Sediba does Suggest a “link” would one then not be able to draw the line back via one of the Australopithecus ?

    1. ThQ says:

      Is it not A. Garhi that is closest to us ? Also about Paranthropus, there is no agreement about whether they are Australopithecines (robust Australopithecines that is) or outside of the Australopithecines.

      1. Adam Benton says:

        We have a Garhi jaw. It’s an interesting jaw, but without more of the skeleton it’s difficult to make too many evolutionary inferences.

        Also I think that there’s a growing consensus that Paranthropus as a distinct genus is a thing.

    2. Adam Benton says:

      Sediba has a unique gait that suggests it isn’t as closely related to humans as first thought. Of course, that gait is present in modern humans as a pathology; so it may be we’ve found some disabled sediba and the species norm was much closer to the human norm. If that’s the case then sediba would again be a great “link” between the two genera, but until we find more specimens we can’t say if that’s the case.

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  6. Skeptiko says:

    “But it doesn’t mean they aren’t part of our family.”

    But being part of our family doesn’t mean they couldn’t also be ancestors of chimps and gorillas, does it?

    1. Adam Benton says:

      The hominins is our “family”. It is the branch of apes that split from the others 7 million years ago. No other branch has since split from us. Thus any member of the hominins cannot be the ancestor of another extant ape.

  7. Skeptiko says:

    It’s from 1990, but maybe still debatable:

    “African ape ancestry
    M. J. B. Verhaegen

    Abstract
    It is commonly believed that the australopithecines are more closely related to humans than to African apes. This view is hardly compatible with the biomolecular data which place theHomo/Pan split at the beginning of the australopithecine period. Nothing in the fossil hominid morphology precludes the possibility that some australopithecines were ancestral to gorillas or chimpanzees and others to humans.”

    http://link.springer.com/article/10.1007%2FBF02437246

    Some other biomolecular data seem to allow for an earlier split though, as old as 10mya I guess.

    1. Adam Benton says:

      That paper seems to be mostly based on old dates for the various splits in the ape family. We diverged from the chimps some point between 5 – 7 mya (although some re-estimates may push this up to ~10 mya) whilst the gorillas split from the chimp/human common ancestor ~12 mya. As such Australopiths (who lived between 4 – 2 mya) comfortably fall within the hominins, after we split from all other apes.

      In other words, a fossil living after ~5-7 mya will only be part of one branch, either human, chimp or gorilla.

  8. Eoanthropus sapiens says:

    Back in 2006 or so, there was an article suggesting that humans and chimps could have had a “complex” split, having interbred at least episodically, or at least for a last time, as recently as 1 mya. I wonder how certain can we be about the traditional/classic “splitting-branch only” phylogenetic scheme. Could hybrid taxons be inferred or “detected” naturally by cladistics or some other method? Or is it generally something out of consideration, and no method would naturally point to such instances, if there are any? The closest thing that come to my mind are these genetic studies on recent human evolution, suggesting that at least at this “lower level” (or a single ceno-species or more closely related species) there seems to be some level of hybridization going on, even though it’s not a “perfect”, 50:50 blending of two lineages.

    I wonder what will come out of similar studies with the genomes of other apes. Would they have their own episodes of “archaic-chimp/gorilla/orangutan admixture” as well? And at which point such episodes could extent? Certainly episodic archaic hybridization wouldn’t be an exclusivity of “modern” species, the archaics would have had some history of hybridation to “their own” archaics… I find unlikely that such notion could easily be ruled out, and I wonder what type of “noise” could be seen from that, perhaps what looks like “more recent” archaic admixture could even be baggage from even earlier episodes of admixture.

    If chimpanzees were actually hybrids of an hominin lineage (or more specifically Australopiths and their ancestors or perhaps very early Homo, those who are even sometimes classified as Australopithecus by some authors, like abilis), with a “gorilla lineage” (whatever that was), what would we expect to find out, genetically and morphologically? And could even be a series of inter-taxon hybrid steps, perhaps, like with Paranthropus in between, if we don’t call those Australopithecus… or those perhaps could be a different hybrid line, with a higher share of gorilla than Homo, compared with the Pan line…

    Interestingly enough, google gives 0 results for both “anatomically modern chimpanzees” and “anatomically modern gorillas”. It’s them, not us, who have the “missing links” in their evolution, perhaps because they’re simply unknown, but maybe it’s also something that wouldn’t even be expected to be ever found from hybrid lines, with “intermediates” existing only in a much more “punctuated” fashion?

    1. Adam Benton says:

      There are next to know fossils of gorilla or chimp ancestors, primarily because they live in a jungle environment; arguably one of the least conducive to mineralisation. As such, you don’t need to start discussing hybrids to explain the paucity of the great ape fossil record. That said, I don’t think you’re completely wrong. Biology is a messy thing and there was likely some continued back and forth between the chimp and human lineages for a fair bit of time. The sudden dramatic split often portrayed in phylogenetic trees is an abstraction at best.

      That said, when genetic research has been done into the issue – to the best of my knowledge at least, genetics is not my strong suite – the conclusion has been that such intermingling was over and done with by around 5 million years ago. No recent chimp hybrids, sorry.

  9. Eoanthropus sapiens says:

    Possibly related:

    Gorilla-like anatomy on Australopithecus afarensis mandibles suggests Au. afarensis link to robust australopiths
    Yoel Rak * , † , Avishag Ginzburg *, and Eli Geffen ‡
    *Department of Anatomy and Anthropology, Sackler Faculty of Medicine, and
    ‡Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
    Edited by David Pilbeam, Harvard University, Cambridge, MA, and approved February 26, 2007 (received for review July 28, 2006)

    Abstract
    Mandibular ramus morphology on a recently discovered specimen of Australopithecus afarensis closely matches that of gorillas. This finding was unexpected given that chimpanzees are the closest living relatives of humans. Because modern humans, chimpanzees, orangutans, and many other primates share a ramal morphology that differs from that of gorillas, the gorilla anatomy must represent a unique condition, and its appearance in fossil hominins must represent an independently derived morphology. This particular morphology appears also in Australopithecus robustus. The presence of the morphology in both the latter and Au. afarensis and its absence in modern humans cast doubt on the role of Au. afarensis as a modern human ancestor. The ramal anatomy of the earlier Ardipithecus ramidus is virtually that of a chimpanzee, corroborating the proposed phylogenetic scenario.

    Natural hybridization in primates: One evolutionary mechanism
    Michael L. Arnolda, , , Axel Meyerb

    Abstract
    The role and importance of natural hybridization in the evolutionary histories of animal taxa is still debated. This results largely from a history of zoological investigations that assumed, rather than documented, a limited evolutionary role for this process. However, it is now becoming apparent that, just as for plants, the creative effects of reticulate evolution are widespread in animal taxa as well. This conclusion is supported by the documentation of numerous instances of the formation of new taxa and the genetic enrichment through introgressive hybridization. In the present review, we use primates as a paradigm for how natural hybridization can affect the evolution of species complexes and remains a footprint on genomes. Findings for a number of groups, including basal (e.g. lemurs) and derived (e.g. Old World apes) lineages, demonstrate that introgression and hybrid speciation have caused a reticulate pattern that is still detectable in the, often mosaic, genomes of primates. For example, results from genetic analyses of our own species demonstrate the process of past introgressive hybridization with the progenitors of our sister taxa (i.e. chimpanzees and gorillas) and most likely also our extinct, close relatives in the hominid lineage.

    1. Adam Benton says:

      Rak et al’s research is very interesting but – and I say this in the nicest possible way – riddled with fairly hefty flaws. For starters the presence of these features in gorillas suggest they are a poor autopomorphy for defining lineages. They reckon they can reliably identify lineages with around 80% accuracy using this approach, which is impressive (and why I say this work is interesting) but still not high enough to overturn almost all the other literature on the subject. Secondly, the jaw tends to be highly variable as a result of functionality rather than ancestry so isn’t a great way of defining lineages (which is the same reason I’m skeptical of similar claims about the jaws of the fossil from Atapuerca; with people arguing their jaws show they aren’t related to Neanderthals despite looking like them in almost every other way). Finally, when the same structure is examined in other species of Australopithecus it is found to be very similar. In other words, it seems the Australopiths developed a “unique” jaw, which they passed on to the Paranthropines, before loosing by the time of Homo.

  10. David Atkins says:

    What a fascinating discussion of a complex subject. On the subject of interbreeding or hybridization between closely related species, my hunch is that it must have happened quite often given the human male’s love of copulating. This is obviously a subjective opinion, not a scientific one but it is also hard to draw firm scientific conclusions on the basis of such scanty and incomplete evidence as fossil remains.
    And can anyone tell me why human evolution began only in Africa as compared to other parts of the southern hemisphere capable of sustaining mammalian life?

    1. Adam Benton says:

      Because that’s where all the apes were.

  11. David Atkins says:

    I am an arts graduate and have little scientific knowledge but I have always been fascinated by human origins. I am glad I found your website which not only disseminates useful information on evolution but allows intelligent discussion and argument by interested lay people rather than just experts in the field

    Why am I so fascinated by this subject? I think it is a mixture of scientific curiosity about where we came from and more philosophical and moral issues such as the role of homo sapiens in……shall I call it .creation’? (But I am not a Creationist; on the contrary I am a rationalist and dislike religion).

  12. marc verhaegen says:

    Thanks for discussing some of my work here.
    AFAIK, prof.Kleindienst was the first to think that australopiths might have been the ancestors of the African apes.
    My Hum.Evol.papers suggest that (most? all?) East-African apiths belong to the genus Gorilla, and (all?) South-African apiths to Pan.
    More specifically about Lucy:

    Gorilla afarensis?

    A.afarensis (DIK-1, Lucy AL-288-1, First Family A-333 etc.) was very Afr.apelike, and more gorilla- than chimp-like, e.g.
    · Johanson & Edey 1981:351: The composite skull reconstructed mostly from A.L.333 specimens “looked very much like a small female gorilla.”
    · Kimbel cs.1984: “Olson’s assertion that the lateral inflation of the A.L.333-45 mastoids is greater than in any extant ape is incorrect if the fossil is compared to P.troglodytes males or some Gorilla males & females. Moreover, the pattern of pneumatization in A.afarensis is also found only in the extant apes among other hominoids… Prior to the identification of A.afarensis the asterionic notch was thought to characterize only the apes among hominoids. Kimbel & Rak relate this asterionic sutural figuration to the pattern of cranial cresting & temporal bone pneumatization shared by A.afarensis & the extant apes.”
    · Bromage & Dean 1985: “Plio-Pleistocene hominids had markedly abbreviated [enamel] growth periods relative to modern man, similar to those of the modern great apes.”
    · Martin 1985: “Enamel thickness has been secondarily reduced in the African apes and also, although at a different rare and extent, in the orang-utan. Thick enamel, previously the most important characteristic in arguments about the earliest hominid [= relative of Homo rather than of Pan –MV], does not therefore identify a hominid.”
    · Ferguson 1987: “A.afarensis is much more similar cranially to the modern African apes than to modern humans.”
    · Franciscus & Trinkaus 1988: “The total morphological pattern with regard to the nasal region of Australopithecus can be characterized by a flat, non-protruding nasal skeleton which does not differ qualitatively from the extant non-human hominoid pattern, one which is in marked contrast to the protruding nasal skeleton of modern H.sapiens.”
    · Schoenemann 1989: A.afarensis type specimen LH-4: “the lower third premolar… is completely apelike.”
    · Ryan & Johanson 1989: “Incisal dental microwear in A.afarensis is most similar to that observed in Gorilla.”
    . Richmond & Strait 2000: A.anamensis ER-20419 & Lucy: “specialized wrist morphology associated with knuckle-walking.”
    . Alemseged cs.2006: DIK-1: “a hyoid that has a typical African ape morphology [i.e. large airsac –MV] … gorillalike scapula and long & curved manual phalanges…”
    . Rak cs.2007: “Mandibular ramus morphology on a recently discovered specimen of A.afarensis closely matches that of gorillas.”
    . Drapeau & Ward 2007: “A.afarensis, represented here by A.L. 288-1, has a slightly shorter humerus for its size than any extant hominoid, although it is extremely close to the gorilla line…”

    In fact, there’s nothing exclusively Homo-like in afarensis:
    – None of the typically-Homo features (eg, external nose, very long legs, very large brain, absent knuckle-walking) are seen in afarensis.
    – All so-called “humanlike” features are “primitive-hominid” (sensu Gorilla+Homo+Pan): Mio-Pliocene hominids & pongids had typically thick or even superthick (eg, Ouranopith) enamel & rel.short canines. Early hominids were short-legged vertical walking-climbing bipeds (predom.wading-climbing? Verhaegen cs.2002).

    In conclusion, there’s nothing that excludes that afarensis (curved phalanges, small brain, even laryngeal airsacs!) might have been a fossil species belonging to Gorilla.

    This is the null-hypothesis:
    A.afarensis was remarkably gorilla-like, and gorillas live in Africa, so everybody who believes for some reason (other than traditional paleo-anthropological biases) that afarensis did not belong to Gorilla should let us know why he believes that. As long as he can’t, the null-hypothesis is that afarensis is a fossil species belonging to the genus Gorilla.

    The same (even more so) is true for A.aethiopicus & for A.boisei (see e.g. my Human Evolution papers):
    A.aethiopicus-boisei are very gorilla-like:
    – body size & sexual dimorphism,
    – humerus & ulna lengths,
    – skull crests,
    – enamel microwear & prism decussation,
    – orbital morphology,
    – basi-cranial pneumatisation,
    – maxillary sinus morphology etc.
    A.aethiopicus-boisei have nothing uniquely-Homo: thick enamel, short canines, short(low) iliac blades & short-legged partial bipedalism are primitively-hominoid.
    In short, all information we have today suggests that the E.African chronospecies afarensis-aethiopicus-boisei belonged to the genus Gorilla (possibly this includes anamensis, bahrelghazali etc., but I lack enough information here).

    In the same way, the S.Afr.apiths africanus-robustus are clearly more Pan- than Gorilla- or Homo-like (e.g. my Hum.Evol.papers). They have nothing exclusively-Homo (their humanlike features are primitive for all hominids sensu Pan-Homo-Gorilla).
    So it’s most parsimonious to place the S.Afr.chronospecies africanus-sediba-robustus-crassidens into the genus Pan.

    In conclusion, AFAICS we have provisionally:
    – Gorilla (Praeanthropus) afarensis, aethiopicus, boisei,
    – Pan (Australopithecus) africanus, sediba, robustus,
    – Homo erectus, georgicus, ergaster, neanderthalensis, floresiensis, sapiens etc.

    The so-called genera “Australopithecus” & “Paranthropus” are paraphyletic.
    IMO, the S.Afr.apiths evolved partly in parallel to the E.Afr.apiths, presumably in response to the same climatic changes: from gracile (africanus // afarensis) in wetter & more forested milieus to robust (robustus // boisei) in drier & less forested milieus (in fact, AFAIK all apiths lived in wetlands).

    Google e.g. “marc verhaegen human evolution” for more information.

    1. Adam Benton says:

      The knuckle walking traits identified by Richmond and Strait have yet to actually be linked to knuckle walking. In fact, many of them don’t actually exist in the fossils; being an artefact of the broken casts the studied. Additionally, there doesn’t seem to be any evidence that Australopiths were evolving towards knuckle walking. An examination of the adaptations for the behaviour in the vertebral column of African apes places Australopiths (and humans) in a very distinct out-group.

      This absence of such a fundamental part of gorilla anatomy would seem to be a very big point against Australopiths being closely related to them.

      1. marc verhaegen (@m_verhaegen) says:

        The Richmond-Strait paper says Lucy has a few features that are also seen in knuckle-walkers. They believe these features are left-overs from KWing. More likely, these features suggest incipient KWing. There are very diverse indications that humans never had KWing ancestors. Google e.g. “marc verhaegen human evolution” or “australopithecines african ape ancestors”.

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