Mutation Rate in Humans Has Slowed Down

I am not quite sure what this means, yet. Researchers at the Aarhus University, Denmark, and the Copenhagen Zoo have discovered that, when compared to our nearest taxonomic relatives, our mutation rates have slowed down. Science Daily has the scoop:

"Over the past six years, several large studies have done this for humans, so we have extensive knowledge about the number of new mutations that occur in humans every year. Until now, however, there have not been any good estimates of mutation rates in our closest primate relatives," says Søren Besenbacher from Aarhus University.

The study has looked at ten families with father, mother and offspring: seven chimpanzee-families, two gorilla families and one orangutan family. In all the families, researchers found more mutations than would be expected on the basis of the number of mutations that would typically arise in human families with parents of similar age. This means that the annual mutation rate is now about one-third lower in humans than in apes.

Why is this important for the study of human origins?

The higher rates in apes have an impact on the length of time estimated to have passed since the common ancestor of humans and chimpanzees lived. This is because a higher mutation rate means that the number of genetic differences between humans and chimpanzees will accumulate over a shorter period.

If the new mutation rates for apes are applied, the researchers estimate that the species formation (speciation) that separated humans from chimpanzees took place around 6.6 million years ago. If the mutation rate for humans is applied, speciation should have been around 10 million years ago.

The six-to-eight million year point for the LCA never made a whole lot of sense to me. If the fossil material from Orrorin, at 6 mya really does reflect bipedality, then the split has to have been much earlier.  The material from Ardipithecus kadabba is very sketchy with regard to bipedalism (one toe bone found ten miles away), but the fragmentary post-cranial bones can be confidently identified as being hominin, in nature.  Furthermore, the fossil material is dated to between 5.6 and 5.8 mya.  That would leave a very short period of time.  It cannot be pre-split because the fossil material exhibits derivations in the hominin direction, rather than the modern ape direction. 

If this study holds up, it will change how we view the search for the LCA. 

Did the LCA Have Teeth More Like a Gorilla?

Artificial intelligence is playing a role in understanding human evolution.  From the Australian site News.com comes a story about new work in trying to understand what the last common ancestor to apes and humans might have looked like:

IT’S an image imprinted on our brains: the steady march of evolution from chimp to human. But it’s not quite right.

Monkeys don’t belong on the tree. They have tails.

Chimps, which don’t, are with Bonobos our closest living relatives. And, as such, both should be standing alongside us in the march of life.

Stretching out behind should be a gradually converging branch of earlier variations.

Ultimately, between six and eight million years ago, the branches almost certainly converge on one common ancestor.

We know almost nothing about what that was.

We have reasonably secure evidence of bipedality at around 6 million years in the form of Orrorin tugenensis from Kenya, as well as a crushed skull from Chad called Sahelanthropus that may or may not be 7 million years old, and recently, fossil footprints, purporting to show bipedal walking, from Crete have been uncovered that have been dated to around 5.7 million years ago.  Beyond that, nothing.  That is where the new AI study comes in.

The researchers used machine learning to teach an artificial intelligence to identify and classify fossilised hominid teeth dating from 25 million years ago. It then sifted through these to find patterns of development.

The study published in the science journal PaleoBios found one tantalising tip.

Our common ancestor almost certainly had gorilla-like teeth.

Now, it’s not a lot. And it certainly doesn’t say our ancestor was a gorilla.

But what it does do is add some shape and substance to this nebulous period of our human origins.

The information that is contained in the article is not nearly as cut and dried as is indicated by the news story. From the conclusion:

Given that the divergence of humans and chimpanzees occurred in the late Miocene, and that Miocene apes are much more similar to Gorilla in dental proportions, we assert that gorillas are the more appropriate extant model for the African ape LCA in terms of the relative sizes of the postcanine teeth. This similarity in dental proportions likely has implications for the interpretation of dietary adaptation and possibly phylogenetic relationships in Miocene apes, including the chimpanzee-human last common ancestor.

What this likely means is that, during the Miocene, which was the golden age of the apes, even after the divergence of Gorillas from the main line, there were extant forms that continued to have varying degrees of traits that could be associated with gorillas, presenting a classic case of collateral ancestry.  It is possible that one of the lines eventually led to chimpanzees, while another led to us.  We won't know more until we actually have some fossil remains from that missing time period. 
.

Five Peculiar Fossils

Colin Barras of The New Scientist has a very short, very peculiar article on five hominin fossils that have been used to define new species and addresses the validity of each in very cursory fashion.  The strength of the article is in the links that it provides.  About Sahelanthropos, he writes this:

Features at the skull’s rear suggest it sat atop a vertical spine like that of a human, hinting that S. tchadensis walked upright. To make sure, other fossils will be needed – particularly from the legs. Unconfirmed reports suggest that a thigh bone was found with the skull, but this has not yet been discussed in a scientific paper. With so little evidence to go on, some are sceptical that S. tchadensis can really yet be defined as a hominin rather than some other form of ape – yet.

These are the least of its problems, as it is likely a surface find. Aside from this, when Wolpoff and colleagues examined the cranial base, here is what they found:

The prominence of the nuchal muscles, so important in head balance and loading, and shoulder movements, is enhanced by the significant development of the tuberculum linearum. The point is not that the TM 266 cranial rear and posterior portion of the cranial base was unlike hominids because the region looks like apes, but that TM 266 had a posture that is not upright because the region reflects nuchal functions similar to those of apes.

The foramen magnum - orbit plane angle does not directly address posture or locomotion in these hominoid primates (contra Zollikofer et al., 2005). Without a key postcranial element such as a pelvis or femur, none of these data provide compelling evidence for upright posture or obligate bipedal locomotion, and the various details of the nuchal plane argue against it. This functional implication has a phylogenetic consequence—by itself it is sufficient to disprove the phylogenetic hypothesis that TM 266 was a hominid.

This isn't skepticism. This is the door slamming shut.  It can be a surface find and still be a Miocene ape. In my recent piece for BioLogos, it did not occur to me to include this fossil since there are so many problems with it.  At this point, in Africa, the earliest reasonable evidence we have for hominins is Orrorin tugenensis. 

Read the whole (short) thing.

5.7 Million Year-Old Human Footprints Found on Greek Island of Crete

Great Googlymoogly!  This one is lighting up all over the Internet.  Fossil footprints have been found in the southern Greek Island of Crete, near the village of Trachilos, that appear to have the distinctive heel-toe-off gait of bipedal humans.  The catch? The prints are 5.7 million years old!  From PhysOrg:

Human feet have a very distinctive shape, different from all other land animals. The combination of a long sole, five short forward-pointing toes without claws, and a hallux ("big toe") that is larger than the other toes, is unique. The feet of our closest relatives, the great apes, look more like a human hand with a thumb-like hallux that sticks out to the side. The Laetoli footprints, thought to have been made by Australopithecus, are quite similar to those of modern humans except that the heel is narrower and the sole lacks a proper arch. By contrast, the 4.4 million year old Ardipithecus ramidus from Ethiopia, the oldest hominin known from reasonably complete fossils, has an ape-like foot. The researchers who described Ardipithecus argued that it is a direct ancestor of later hominins, implying that a human-like foot had not yet evolved at that time.

The new footprints, from Trachilos in western Crete, have an unmistakably human-like form. This is especially true of the toes. The big toe is similar to our own in shape, size and position; it is also associated with a distinct 'ball' on the sole, which is never present in apes. The sole of the foot is proportionately shorter than in the Laetoli prints, but it has the same general form. In short, the shape of the Trachilos prints indicates unambiguously that they belong to an early hominin, somewhat more primitive than the Laetoli trackmaker. They were made on a sandy seashore, possibly a small river delta, whereas the Laetoli tracks were made in volcanic ash.

And now, the other shoe.  How do we know how old the fossil footprints are?  

The coastal rocks at Trachilos, west of Kissamos Harbour in western Crete (Fig. 1a–c), lie within the Platanos Basin, and present a succession of shallow marine late Miocene carbonates and siliciclastics of the Roka Formation, a local development of the Vrysses Group (Freudenthal, 1969 ; van Hinsbergen and Meulenkamp, 2006; Figs. 1d, e and 3a, b). At the top, this marine succession terminates abruptly in the coarse-grained terrigenous sedimentary rocks of the Hellenikon Group (Figs. 1d and 3e, f), which formed by the desiccation of the Mediterranean Basin during the Messinian Salinity Crisis (van Hinsbergen and Meulenkamp, 2006), an event dated to approximately 5.6 Ma (Govers, 2009). The succession (Fig. 1d) contains an emergent horizon with well-preserved terrestrial trace fossils and microbially induced sedimentary structures (Fig. 3d) immediately overlying shallow water ripplemark structures (Fig. 3c).¹

So, the authors are a tad more circumspect than the writers of the PhysOrg story.  The authors posit two hypotheses for their results: 1. the tracks represent the gait of a basal hominin, which explains the non-divergence and shape of the big toe as well as the shape of the ends of the other toes, which resemble those of a human foot and not a non-human foot.  This fits approximately with the dates of the north African remains of Orrorin and, perhaps, that of Sahelanthropus (although that is pretty much a surface find).

The Messinian Crisis was a period of time during the Miocene epoch during which the Mediterranean Sea almost completely dried up.  This crisis began around 6 million years ago and ended around 5.3 million years ago with what is known as the Zanclean flood.  It is estimated that once the barrier at the Strait of Gibraltar was broken, the Mediterranean Sea refilled within two years, which means that the sea level rose at an estimated 30 feet per day.

Okay...now, lets go back here, to the story that came out about four months ago, establishing the possibility that the last common ancestor to apes and humans was in Europe.  In that study, a jaw with human root patterns and an isolated premolar that have both been attributed to Graecopithecus, were re-examined and found by the researchers to have hominin affinities, a surprising conclusion, given their age of 7.15 million years.  At the time that story appeared, I remarked that it was a bit of a stretch to hang one's hat on one premolar and partial ape-like mandible, but in the context of the new finds, maybe not so much.  This strengthens the (admittedly far-fetched) notion that our ancestors did, in fact, originate somewhere in southeast Mediterranean Europe and, over the course of the next two and half million years ago, migrated south to north Africa.

As Per Ahlberg was quoted as saying:

"This discovery challenges the established narrative of early human evolution head-on and is likely to generate a lot of debate. Whether the human origins research community will accept fossil footprints as conclusive evidence of the presence of hominins in the Miocene of Crete remains to be seen."

This is huge news.  Even if we can't place the LCA in southern Europe, we now have bipedalism extending back into the late Miocene. 


¹Gerard D. Gierliński et al, Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete?, Proceedings of the Geologists' Association (2017). DOI: 10.1016/j.pgeola.2017.07.006

New Dates For Little Foot Push It Back to Au. afarensis Time-Period

On the heels of the Ledi jaw dates for early Homo at 2.8 million years ago, and the corresponding tentative conclusion that only Au. afarensis could emerge as a possible ancestor for early Homo, to the exclusion of any of the other australopithecines, comes a redating of the Australopithecus specimen from the cave of Sterkfontein to 3.67 million years ago.  From the story in Science Daily:

Ronald Clarke, a professor in the Evolutionary Studies Institute at the University of the Witwatersrand who discovered the Little Foot skeleton, said the fossil represents Australopithecus prometheus, a species very different from its contemporary, Australopithecus afarensis, and with more similarities to the Paranthropus lineage.

“It demonstrates that the later hominids, for example, Australopithecus africanus and Paranthropus did not all have to have derived from Australopithecus afarensis,” he said. “We have only a small number of sites and we tend to base our evolutionary scenarios on the few fossils we have from those sites. This new date is a reminder that there could well have been many species of Australopithecus extending over a much wider area of Africa.”

So, what is Au. prometheus, exactly and how does it differ from the other australopithecines in the area?  From the paper by Granger, et al.¹:

This species was named on the basis of a parietooccipital fossil from Makapansgat23. It has been suggested22 that several other Sterkfontein and some Makapansgat specimens also belong in this species making Australopithecus africanus and A. prometheus contemporaries in the assemblages of Makapansgat Member 3 and Sterkfontein Member 4. A. prometheus differs from A. africanus in features including Paranthropus-like larger, bulbous-cusped cheek teeth, a longer, flatter face, incipient supraglabellar hollowing and a more vertical rounded occiput22. (Note that we use the term hominid in the traditional sense to include humans and their ancestral relatives but exclude the great apes.)

One of the raging debates in human palaeontological studies concerns whether or not the robust australopithecines, Au. robustus and Au. boisei, represent their own clade, Paranthropus. This perspective is based on traits that are shared to the exclusion of other australopithecine species.  Opponents of this view argue that quite a few of the traits that make up this clade are functional in nature, involving mostly the chewing complex, and that as such, Au. robustus and Au. boisei are  outgrowths of Au. africanus.

The story continues, quoting Ron Clarke:

“It demonstrates that the later hominids, for example, Australopithecus africanus and Paranthropus did not all have to have derived from Australopithecus afarensis," he said. “We have only a small number of sites and we tend to base our evolutionary scenarios on the few fossils we have from those sites. This new date is a reminder that there could well have been many species of Australopithecus extending over a much wider area of Africa.”

Hope so, because right now, here is how it looks:

• P. robustus (or Au. robustus) only in South Africa
• P. boisei (or Au. boisei) only in East Africa
• Early Homo only in East and Northeast Africa
• Au. africanus only in South Africa
• Ar. ramidus only in North East Africa
• Au. afarensis only in North East Africa

As Slim Pickens would say: “What in the Wide, Wide World of Sports is a-goin' on here?”

All of this sort of leads to the question of who the last common ancestor of humans and modern apes was.  All we have to go on is a badly crushed skull from the Sahel River area in Chad that is purported to be somewhere around 7 mya, but is, in reality, a surface find, and some hominin-looking post-cranial remains from the Tugen Hills, in Kenya that are dated to between 5.6 and 6.1 mya.  By the time we get to Ar. ramidus, at least facultative bipedalism is in place, although there are still quite a few ape-like traits.  What is not clear from the report by Granger et al, is how the morphology compares to earlier hominins.  For example, can the traits observed in Au. prometheus be derived from Ar. ramidus?  If so, then it still represents a possible precursor and something like Ar. ramidus gave rise to both the australopithecines and the paranthropines.  The fact that the discoverers are calling it Australopithecus suggests that it shares enough derived traits with the australopithecines as a whole to be called that.  If the traits cannot be derived from Ar. ramidus, then it raises the possibility that the paranthropines and Ar. ramidus share a common ancestor.  At this point, until some systematic analyses can be done, we simply don't know. 

Of course, all of this is contingent on the dates holding up.  The article gives a pretty good run-down on how isochron dating works and indicates that the dates are consistent with what would be expected given the deposition.   I am sure that more will come out about this very shortly.  Until then...

¹Darryl E. Granger, Ryan J. Gibbon, Kathleen Kuman, Ronald J. Clarke, Laurent Bruxelles, Marc W. Caffee. New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan. Nature, 2015

BioLogos, Ken Ham and David Menton—A Response, Part VI: The Conclusion

This concludes my response to David Menton's post on human origins, which has been a chore to read and respond to. Menton's conclusion is so short, I will post it in its entirety:

Why then are there continued efforts to make apes out of man and man out of apes? In one of the most remarkably frank and candid assessments of the whole subject and the methodology of paleoanthropology, Dr. David Pilbeam (a distinguished professor of anthropology) suggested the following:

Perhaps generations of students of human evolution, including myself, have been flailing about in the dark; that our data base is too sparse, too slippery, for it to be able to mold our theories. Rather the theories are more statements about us and ideology than about the past. Paleoanthropology reveals more about how humans view themselves than it does about how humans came about. But that is heresy.

Oh, that these heretical words were printed as a warning on every textbook, magazine, newspaper article, and statue that presumes to deal with the bestial origin of man!
No, we are not descended from apes. Rather, God created man as the crown of His creation on Day 6. We are a special creation of God, made in His image, to bring Him glory. What a revolution this truth would make if our evolutionized culture truly understood it!

First, David Pilbeam wrote that almost forty years ago, and yet Menton appears to hold it up as current scholarship.  You wouldn't do that in any legitimate scientific discipline.  It may be a good example of “look what we thought back then,” in a historical sense and as compare and contrast but not current thought.  This is a typical young earth creationist tactic: find a useful quote and keep using it, long after it is no longer true or has been debunked.  As such, it is no different than using (or abusing) Solly Zuckerman's quote from the early 1970s.  I saw Duane Gish at the University of Tennessee a few years back he used Zuckerman's quote as well.  Once a quote is found, it makes the rounds.

Pilbeam's quote comes from a review of Richard Leakey's book Origins and is found in the American Scientist (Vol. 66, No. 3, May-June 1978).  Let's see what Pilbeam thinks about palaeoanthropology as of 1995:

The discovery of an australopithecine mandible together with a middle Pliocene fauna 2,500 km west of the Rift Valley considerably extends the known range of these early hominids and raises several interesting issues. The Chad specimen is most similar to its East African contemporary A. afarensis. Nevertheless, in certain features-mandibular morphology, premolar roots and enamel thickness- it differs from the described hypodigm of A. afarensis . Given the genetic and morphological differences now recognized between allopatric populations within, for example, Pan troglodytes, Gorilla gorilla, Pongo pygmaeus and Papio hamadryas as well as other African mammals, it is not surprising that contemporaneous hominid populations as geographically distant as Chad and Ethiopia, Kenya and Tanzania would differ in morphology, regardless of whether they are classified as species or subspecies. Here we do not choose to name a new species, recognizing that more detailed comparisons are necessary before the taxonomy of this Bahr el Ghazal hominid can be resolved.¹

Here, he and the other authors of the paper clearly feel that the state of the discipline is sound enough to make educated pronouncements about the fossil record.  In all of Pilbeam's papers, it is clear that he is committed “evolutionist.” As with all palaeoanthropologists, he accepts that there may be aspects of the study that are not known or poorly understood but, of the central tenet: that humans have evolved, there is clearly no doubt.  Thirty six years is a long time in the history of a scientific discipline.

How good is our understanding of the human fossil record now?  Here is what another distinguished professor of anthropology, Richard Klein, has to say:

In the absence of fossils, Darwin could not have predicted the fundamental pattern of human evolution, but his evolutionary theory readily accommodates the pattern we now recognize. Probably the most fundamental finding is that the australopithecines, who existed from at least 4.5 million to 2 million years ago, were distinguished from apes primarily by anatomical specializations for habitual bipedalism, and it was only after 2 million years ago that people began to acquire the other traits, including our unusually large brains, that readily distinguish us from the living apes. The greatly expanded fossil record shows that the australopithecines comprised multiple species, and it suggests that our own genus, Homo, descended from one of these about 2.5 million years ago.²

Note the phrase “the greatly expanded fossil record.” Recall the two compendia on this fossil record I mentioned in the first part of this response. Menton clearly is unfamiliar with this record and his attempts to discredit it are shallow, as a result.

To recap:

• He claims that “evolutionists” just accept similarities between fossil bones of living men and fossilized apes as evidence of ancestry. Such a statement betrays a lack of understanding of homology, functional morphology and the modern study of evolutionary systematics. It glosses over important skeletal structures that arose during our ancestry and which separate our direct ancestors from all apes, fossil or otherwise.
• He massively under-emphasizes the size of the human fossil record and the complexity of it, simply dismissing it with no examination or explanation.
• He suggests that research projects cannot be undertaken based on pictures and measurements of fossil hominins.  This is absurd.  There is no scientific discipline that does not rely on published reports.  Moreover, this is a peculiar statement coming from a professor of anatomy, who must have, during his tenure as a professor, read countless articles on aspects of anatomy in which there were published measurements and pictures.  What was he to make of those?  Did they not constitute real research on which he based his own?
• He mistakenly calls a spider monkey an ape, bringing into question his understanding of basic primate taxonomy.  Further, while his anatomical specialty seems to have been at the cellular level, he betrays a peculiar lack of understanding of human morphological functional interrelatedness by suggesting that the carrying angle of hominins can be dissociated from hip, limb and cranial morphology.  While it may be true that some apes have a similar carrying angle to humans, not a one of them has a foramen magnum at the base of the skull, angled femoral condyles, or a flat, wide pelvis.  Further, these derived traits show up in the fossil record around 3.7 million years ago.  How did he miss these things?  When I took gross anatomy and physiology, I was required to learn not just developmental biology, but functional and comparative morphology.  Has he forgotten his?
• He writes that Ardipithecus, Orrorin, Sahelanthropus, and Kenyanthropus all have “obviously ape skulls, ape pelvises, and ape hands and feet” despite the fact that only one of these finds preserves the skeletal parts he references. This suggests that he never even bothered to look at the reports detailing these finds.  To make such errant, blanket statements about them is incompetent and sloppy. 
• He cherry-picks quotes that support his position and ignores ones that do not.  While he calls A. afarensis “long-armed knuckle-walkers” and suggests that palaeoanthropologists Stern and Susman³ argue that it is an ape, he carefully ignores other paragraphs from their article, in which they clearly argue that it is transitional between apes and humans, even using the phrase “missing link.”  He then (again, oddly for an anatomist) ignores other critical morphology of A. afarensis that clearly indicates its transitional status.
• He writes that Neandertals were considered human but have recently been denigrated to non-human status, when in fact, that is precisely backwards.  From their initial discoveries, Neandertals were considered subhuman^4,5 and it has only been within the last thirty years that their relationship to modern humans has been reassessed, inviting claims by some that they represent simply an earlier version of us and incorporating new genetic knowledge of interbreeding between Neandertals and modern humans⁶.  

This is a badly written post that shows little in the way of actual research.  He seems to misunderstand basic anatomy, gets fossil descriptions wrong, quote-mines to show only what appears to support his position and seems to show no understanding of basic evolutionary biology.  His demeanor is pompous and contemptuous and his treatment of the subject matter invites scorn.

I have absolutely no doubt that Dr. Menton is a bible-believing Christian and that, as such, he is an asset to the kingdom.  I also believe that, like so many other young-earth creationists I am familiar with, he treats the fossil material and the discipline of evolutionary biology with dishonesty and lack of integrity.  This saddens me since it, as with all of creation, reflects the goodness, glory and, importantly, the awesomeness of God.  Further, it is a bad witness and pushes people away from God. 

¹Brunet, M, Beauvilain, A, Coppens, Y, Heintz, E, Moutaye, A, Pilbeam, D. (2014) The first australopithecine 2,500 kilometres west of the Rift Valley (Chad). Nature 378, November 16, 1995
²Klein, R. G. (2009). Darwin and the recent African origin of modern humans. Proceedings of the National Academy of Sciences, 106(38), 16007-16009.
³Stern Jr, J. T., & Susman, R. L. (1983). The locomotor anatomy of Australopithecus afarensis. American Journal of Physical Anthropology, 60(3), 279-317.
⁴Boule, M. (1913). L'homme fossile de La Chapelle-aux-Saints: Masson.
⁵Virchow, Rudolf. Untersuchung der Neanderthal Schädels. 1872.
⁶For example: Sankararaman S, Patterson N, Li H, Pääbo S, Reich D (2012) The Date of Interbreeding between Neandertals and Modern Humans. PLoS Genet 8(10): e1002947. doi:10.1371/journal.pgen.1002947
⁷Krings, M., Stone, A., Schmitz, R. W., Krainitzki, H., Stoneking, M., & Pääbo, S. (1997). Neandertal DNA sequences and the origin of modern humans. Cell, 90(1), 19-30.

BioLogos, Ken Ham and David Menton—A Response, Part IV

This is the fourth part of my response to David Menton's post on human origins.  Links to the first three appear below this post.  Menton continues his ham-fisted, ignorant attack on the human fossil record.

Point 8.  He writes:  

Many apemen are merely apes that evolutionists have attempted to upscale to fill the gap between apes and men. These include all the australopithecines, as well as a host of other extinct apes such as Ardipithecus, Orrorin, Sahelanthropus, and Kenyanthropus. All have obviously ape skulls, ape pelvises, and ape hands and feet. Nevertheless, australopithecines (especially Australopithecus afarensis) are often portrayed as having hands and feet identical to modern man; a ramrod-straight, upright posture; and a human gait.

The best-known specimen of A. afarensis is the fossil commonly known as “Lucy.” A life-like mannequin of “Lucy” in the Living World exhibit at the St. Louis Zoo shows a hairy, humanlike female body with human hands and feet but with an obviously apelike head. The three-foot-tall Lucy stands erect in a deeply pensive pose with her right forefinger curled under her chin, her eyes gazing off into the distance as if she were contemplating the mind of Newton.

Few visitors are aware that this is a gross misrepresentation of what is known about the fossil ape Australopithecus afarensis. These apes are known to be long-armed knuckle-walkers with locking wrists. Both the hands and feet of this creature are clearly apelike. Paleoanthropologists Jack Stern and Randall Sussman2 have reported that the hands of this species are “surprisingly similar to hands found in the small end of the pygmy chimpanzee–common chimpanzee range.” They report that the feet, like the hands, are “long, curved and heavily muscled” much like those of living tree-dwelling primates. The authors conclude that no living primate has such hands and feet “for any purpose other than to meet the demands of full or part-time arboreal (tree-dwelling) life.” 

Some background involving the Miocene apes. At the beginning of the Miocene epoch, apes had largely generalized skeletal structures, with few of the adaptations that we see in the modern apes, or in humans.  Toward the end of the Miocene, biomechanical adaptations are seen in many of the apes.  For example, Oreopithecus has developed a locomotor pattern seen in modern non-human apes (although it was mis-identified by Casey Luskin as bipedal).

Menton, having taken us through the differences between apes and humans, suggests that Ardipithecus, Orrorin, Sahelanthropus and Kenyanthropus all have “obviously ape skulls, ape pelvises, and ape hands and feet.”

Really?

• Kenyanthropus consists of a single skull find that is so badly crushed that most researchers have pretty much written it off as being unusable in taxonomic reconstruction.
• Sahelanthropus is also a single skull find that was also crushed and may, in fact, be a surface find.
• Orrorin tugenensis is a collection of post-cranial remains, the most important of which is a partial femur, which showed clear adaptations toward bipedality. 
• Ardipithecus ramidus consists of both cranial and post-cranial remains, including both hands and feet.  Here is what Owen Lovejoy and colleagues wrote about it in 2009:

“The gluteal muscles had been repositioned so that Ar. Ramidus could walk without shifting its center of mass from side to side. This is made clear not only by the shape of its ilium, but by the appearance of a special growth site unique to hominids among all primates (the anterior inferior iliac spine). However, its lower pelvis was still almost entirely ape-like, presumably because it still had massive hindlimb muscles for active climbing.”

How does Menton describe the locomotion of modern apes?  He writes:

These animals manage to keep their weight over their feet when walking by swinging their body from side to side in the familiar “ape walk.” 

Yet he calls Ardipithecus “merely” an ape. By his own description, Ardipithecus is clearly not “merely” an ape. Did he just miss this detail, or did he simply choose not to include it?

To recap this point,  he writes that all of the finds he mentions have “obviously ape skulls, ape pelvises, and ape hands and feet,” and yet we find that only one of the finds has those body parts preserved.  He, further, ignores critical morphology on the Ardipithecus remains to make it seem as if it has no hominin adaptations.  How are we to believe what he writes when he so incompetently describes the fossils he is denigrating?

Point 9: In quoting Stern and Susman, here, again, Menton picks and chooses what he wants to use and doesn't tell his audience other critical information that undercuts his position.  Menton writes as if Australopithecus afarensis were only an ape, yet Stern and Susman write, in their conclusion:

In our opinion A. afarensis is very close to what can be called a “missing link.” It possesses a combination of traits entirely appropriate for an animal that had traveled well down the road toward full-time bipedality, but which retained structural features that enabled it to use the trees efficiently for feeding, resting, sleeping, or escape. prior to the discovery of the Hadar remains, one could not have predicted precisely what combination of traits would be found in a transitional form such as A. afarensis.

These writers, who, unlike Menton, examined the remains directly, clearly did not conclude it was merely an ape but, in fact, a transitional form between the apes that came before, and the hominins that came after.

But worse, Menton completely ignores other characteristics of A. afarensis that don't just undercut his position that it is merely an ape, they destroy it. 

• The first premolar in apes (or bicuspid if you prefer) is long and rotated toward the front of the mouth. This is so it can constantly sharpen the maxillary canine as the ape bites down. This is known as a "sectorial premolar". In humans, this tooth is rotated so that the cusp division is parallel to the tooth row and does not stick up beyond it. The maxillary canine is, correspondingly, short. In Australopithecus afarensis, this tooth is rotated HALF-WAY and partially sticks up from the tooth row. The canine is shortened as in modern humans.

• The palate of the mouth in apes is shaped like a hard "U" with the back teeth parallel to each other. In humans, the palate is more "V" shaped. In A. afarensis, it is intermediate between these two shapes.

• In apes, there is a distinct space between the canine and the first premolar, called a diastema. In humans, this space is absent. In A. afarensis, a diastema is present but it is remarkably reduced in size over the ape condition.

In other instances, some characteristics are completely ape-like and some are completely human-like. For example:

• The digits (phalanges) on both the hands and feet are curved, as in apes. In humans, they are straight.

• The pelvis is flared (wide from side to side) and short from top to bottom, as in humans.

• The hole in the skull where the spinal chord exits the brain, the foramen magnum, is located on the bottom of the skull in Australopithecus afarensis, as in humans.  Having a hole at the base reflects a bipedal gait.

• the knee joint, which preserves the bottom (distal) section of the femur and the top (proximal) section of the tibia shows that the femur is angled, as in humans. This is the "carrying angle" of which Menton wrote. The A. afarensis position, once again, reflects bipedalism.

These characteristics are exactly what you would expect to find in a transitional species: some characteristics transitional, some ape-like and some human-like. Most of the above information was taken from Lucy: The Beginnings of Humankind and Johanson et al. (1982) but can be found in most textbooks about this subject.  It is amazing that Menton went to no effort to locate this information before dismissing A. afarensis' transitional status without thought.    It is, further, amazing that Ken Ham would hold Menton's post up as being authoritative when it is so badly researched and written.

On to Part V. 

New Study: Ardipithecus ramidus Derived In Human Direction

According to Bill Kimbel and colleagues, the skull of Ardipithecus ramidus shows tell-tale signs of being derived in the human direction away from great apes.  From Science Daily:

White's field-research team has been recovering fossil remains of Ardipithecus ramidus in the Middle Awash research area, Ethiopia since the 1990s. The most recent study of the Ardi skull, led by Suwa, was published in Science in 2009, whose work (with the Middle Awash team) first revealed humanlike aspects of its base. Kimbel co-leads the team that recovered the earliest known Australopithecus skulls from the Hadar site, home of the "Lucy" skeleton, in Ethiopia.

"Given the very tiny size of the Ardi skull, the similarity of its cranial base to a human's is astonishing," says Kimbel.

The cranial base is a valuable resource for studying phylogenetic, or natural evolutionary relationships, because its anatomical complexity and association with the brain, posture and chewing system have provided numerous opportunities for adaptive evolution over time. The human cranial base, accordingly, differs profoundly from that of apes and other primates.

In humans, the structures marking the articulation of the spine with the skull are more forwardly located than in apes, where the base is shorter from front to back and the openings on each side for passage of blood vessels and nerves are more widely separated.

Given that the post-cranial remains from Ardipithecus suggest facultative bipedalism, this is not so surprising. If you are going to walk upright at all, you need to be able to see where you are going. This information, in conjunction with the new appraisal of the Orrorin tugenensis remains strongly suggests that, while Orrorin was at or near the junction of the last common ancestor, Ardipithecus, at 1.6 million years later, is quite a bit beyond it. It also reinforces what a terrible model the modern apes are for early human morphology.