Todd Wood's Take on Danuvius

Todd Wood is always interesting to read, even if I don't share his chronological leanings.  He has thoughts on the new Miocene ape from Bavaria, Danuvius:

Based on the fragmentary remains, we make some really interesting observations about the anatomy of Danuvius. These apes had strongly opposed big toes, which would allow them to effectively grip things with their feet. Their tibiae (shinbones) have the kinds of joints that would allow them to walk upright, and their femora (thighbones) support that conclusion. These apes might have been in some way bipedal. The arm bones they found have traits that are associated with suspensory locomotion, like hanging from tree branches. The body size was fairly small, about the mass of a bonobo.

As I mentioned in my post, I think the evidence for bipedalism is vastly over-stated and, even if it can be shown that this “Extended Limb Clambering” is shared by other fossil ape finds from the region, there is no particular reason to think that these critters were ancestral to later hominins. It is entirely likely that they exhibited a separate adaptation to this particular style of locomotion.  Todd raises some other questions, though, that are not answered in the paper:

So why not address similarities of Danuvius to later fossil hominins? The authors are trying to establish a new means of locomotion that they call Extended Limb Clambering (ELC). So they compare Danuvius to living primates (where the authors know how they get around), and they're interested in comparing it to contemporary Miocene apes of Europe. But they're not all that excited about other comparisons to later fossil forms like Ardipithecus, Australopithecus, or Orrorin. They also don't relate their findings to later fossil apes in Europe like Graecopithecus or the Trachilos tracks, both of which have been linked to hominins or bipedality. Perhaps they don't think those things are worth talking about (maybe because they're skeptical of Graecopithecus like I am), but I guess I just don't agree.

I think that part of the reason that these questions are not raised is because there is so much of a gap between these finds, chronologically and geographically. There is simply with which to relate them. As Todd points out, the hominin status of Graecopithecus is dubious, at best, and, even if the Trachilos tracks are hominin, they are still quite a distance from Bavaria and six million years later in time.

For now, this fossil ape stands on its own.  If we find other evidence of incipient bipedality in other forms in the area and can relate them to later forms, then the picture might change.  For now, though, Danuvius is a very interesting, odd Miocene ape. 

More Evidence For Bipedality at 4.5 MYA

Out of Case Western Reserve comes a study of some new fossil material that sheds like on early human bipedal adaptation.  From ScienceDaily:

Scott W. Simpson, PhD, led an analysis of a 4.5 million-year-old fragmentary female skeleton of the human ancestor Ardipithecus ramidus that was discovered in the Gona Project study area in the Afar Regional State of Ethiopia.

The newly analyzed fossils document a greater, but far from perfect, adaptation to bipedalism in the Ar. ramidus ankle and hallux (big toe) than previously recognized. "Our research shows that while Ardipithecus was a lousy biped, she was somewhat better than we thought before," said Simpson.

While the weight of evidence has always a bit more than slightly favored the facultative bipedality of Ardipithecus ramidus, this research provides greater support for this hypothesis.  In my class, I stress the difference between facultative bipedality (practiced by Ardipithecus) and obligate bipedality (practiced by every other hominin).  Additionally, from the article¹:

The more complete adoption of bipedality in the australopiths resulted in the loss of functionally critical adaptations to arboreality present in Ardipithecus such as a grasping, opposable hallux, an antero-posteriorly broad pelvis with reorganization of the origin (and most likely function) of the hamstring muscles, and a more derived humero-femoral ratio. The changes in the size and structure of the dentition in the subsequent australopiths (larger molar and premolar crowns, increased enamel thickness, more robust mandibles) indicates a major behavioral and dietary shift for most hominins (perhaps excluding the species indicated by the Burtele foot) that occurred about 4.2 Ma with the earliest appearance of Australopithecus (Leakey et al., 1995, White et al., 2006).

Many of these changes, then, appear to have occurred somewhat rapidly, once the early hominins moved away from the forest and into the fringe.  Once we thought that bipedality originated in the forest/fringe.  The Ardipithecus data have killed this hypothesis. 


¹Scott W. Simpson, Naomi E. Levin, Jay Quade, Michael J. Rogers, Sileshi Semaw. Ardipithecus ramidus postcrania from the Gona Project area, Afar Regional State, Ethiopia. Journal of Human Evolution, 2019; 129: 1 DOI: 10.1016/j.jhevol.2018.12.005

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. 

My Favorite Fossil Post Up on BioLogos

Unbeknownst to me, my “My Favorite Fossil” post on BioLogos is up.  You can view it here.  Comments welcome in both places. 

New Laetoli Footprints Demonstrate Full Bipedality

A story running in Newsweek and the Washington Post (and other outlets, presumably), details research into the newly discovered fossil footprints at Laetoli dated to 3.6 mya that clearly show a modern human gait.

Two sites in Laetoli, Tanzania, feature footprints of human ancestors who lived about 3.6 million years ago. They were members of the genus Australopithecus. That's the genus of “Lucy,” the 3.2 million-year-old human ancestor whose fossilized bones were discovered in Ethiopia in 1974.

David Raichlen, an evolutionary anthropologist at the University of Arizona, has studied the Laetoli footprints and compared them to footprints made by human volunteers in laboratory settings. He examined footprints of individuals walking normally and also those walking with bent knees and bent hips. (Scientists who study locomotion use the acronym BKBH). The Laetoli footprints more closely match modern human footprints.

“Upright, humanlike bipedal walking goes back 4 to 5 million years,” Raichlen told The Washington Post in advance of a symposium on the evolution of human locomotion, which took place Sunday at the Experimental Biology 2018 conference in San Diego.

This dovetails with the recent findings that Ardipithecus, a hominin dated to around 4.4 mya, likely could travel equally well on the ground or in the trees.  Oddly, the WaPo article doesn't mention this.  

Ardipithecus May Not Have Been Entirely a Facultative Biped After All

In a new article in the Proceedings of the National Academy of Sciences, several researchers have concluded, using 3D morphometric analysis have discovered that Ardipithecus ramidus, while still having facultative (didn't have to but could) bipedalism, when it did walk, its bipedal gait was nearly human.  From the abstract:

We show that hamstring-powered hip extension during habitual walking and climbing in living apes and humans is strongly predicted, and likely constrained, by the relative length and orientation of the ischium. Ape pelves permit greater extensor moments at the hip, enhancing climbing capability, but limit their range of hip extension, resulting in a crouched gait. Human pelves reduce hip extensor moments but permit a greater degree of hip extension, which greatly improves walking economy (i.e., distance traveled/energy consumed). Applying these results to fossil pelves suggests that early hominins differed from both humans and extant apes in having an economical walking gait without sacrificing climbing capability. Ardipithecus was capable of nearly human-like hip extension during bipedal walking, but retained the capacity for powerful, ape-like hip extension during vertical climbing. Hip extension capability was essentially human-like in Australopithecus afarensis and Australopithecus africanus, suggesting an economical walking gait but reduced mechanical advantage for powered hip extension during climbing.

This positions Ardipithecus as the classic intermediate in terms of bipedal locomotion.Although there are many traits in Australopithecus afarensis that are still transitional in terms of the rib cage, dentition and aspects of the hip, it is clear that the major adaptations for bipedalism were in place nearly a million years earlier.  This also suggests that it is not out of the realm of possibility that the fossil footprints in Crete really do reflect a bipedal hominin.  At the risk of positing heresy, the fact remains that we really don't know exactly where hominins first appeared.  This study also reinforced the distinct separation between apes and humans in terms of iliac shape, and that this split must have taken place even further back in time that we have supposed.

The Independent has a news story on this here.  One of the authors, Herman Pontzer remarks:

“It kicks us out of this old paradigm of thinking about human evolution,”...“In that old picture that is everywhere where you have the evolution of man going from crouching thing to upright thing to a human – as much as we have known that is not right, I still think people have it in their heads.”

Humans and Fire

It had been conventional wisdom that the origin of bipedality occurred in a forest/fringe environment and that a move to the savannah during the dry-out at the end of the Pliocene accelerated the evolution of humans.  That was thrown into turmoil when it was discovered that Ardipithecus ramidus possessed facultative bipedal characteristics at 4.4 million years but lived in an entirely forested environment.

Now, it seems, the savannah is seen as playing a different role in human evolution.  Charles Q. Choi, of Scientific American writes:

A longtime theory holds that early humans discovered how to use fire accidentally—perhaps while making stone tools they found that striking rocks against each other could generate sparks, and then gradually learned fire had many uses.

The problem with such serendipity-based explanations is that they "raise more questions than they answer," says evolutionary anthropologist Christopher Parker at the University of Utah in Salt Lake City. For example, these theories do not address when or where the discovery might have occurred, why it did not happen earlier or why other animals that use stone tools—chimpanzees, capuchin monkeys, crab-eating macaques and sea otters are known to do so—did not also develop fire use, Parker notes.

Parker and his colleagues suggest in a study published in the April Evolutionary Anthropology that humans developed fire use as a natural response to environmental changes. Previous research found that roughly 3.6 million to 1.4 million years ago—as the genus Homo emerged in Africa—the continent regularly experienced bouts of aridity, causing forests to shrink and dry grasslands to spread. Earlier studies suggested these climate shifts may have driven humanity’s ancestors away from a life climbing trees and toward one of walking upright on the ground, Parker says.

Yes, but there have been, as alluded to above, issues with these previous studies. If bipedality originated in the forest, as a response to who-knows-what, then they already possessed it when the drying out began. But this is not the crux of Parker's research:

Parker and his colleagues suggest in the new study that our ancestors not only grew accustomed to fire but learned to exploit it as a naturally occurring resource. This adaptation, called pyrophilia, may have set the stage for more active and deliberate human use of fire.

The research team's models suggest early humans benefited from wildfires in a number of ways: The blazes would have made it easier to find food, much as Martu Aboriginal women in Australia still rely on fire to clear brush for more efficient hunting. The models also indicate that early humans might have combed the charred remains of wildfires to dine on animals, seeds, nuts and tubers cooked in the flames—benefitting from a chemical process that not only makes many foods easier to digest but kills germs and neutralizes some toxins.

This has not been proposed before and it will be interesting to see if more evidence of this is found. Read the whole thing.

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.

Orrorin tugenensis: As Close to the Last Common Ancestor As We Have Gotten?

Based on work by SUNY Stoney Brook, it has been learned that the femur of Orrorin tugenensis, the six-million year-old presumed hominin, also called the "millenium man," has a mix of traits that align it with not just early hominins but late Miocene apes.  Science Daily reports:

According to Dr. Almécija, their study for the first time compared the six-million-year-old Millenium Man femur (called BAR 1002'00) using state-of-the-art morphometric techniques to not only other available hominin fossils but also great apes, hylobatids (ie, gibbons and siamangs), and most importantly to fossil apes that lived in the Miocene. The analysis included more than 400 specimens.

"We discovered that Orrorin's femur is surprisingly 'intermediate' in both age and anatomy between quadrupedal Miocene apes and bipedal early human ancestors," said Dr. Almécija. "Our paper provides quantitative results of the Orrorin femur as a unique mosaic and stresses the need to incorporate fossil apes into future analyses and discussions dealing with the evolution of human bipedalism, an investigation that should stop considering chimpanzees as default living 'starting point' models."

As the authors note, this is not so different from what was concluded about the gait of Ardipithecus ramidus and that the examination of that hominin led to the idea that, perhaps, modern apes are poor models for early hominin morphology and that the modern apes diverged from the last common ancestor (LCA) in entirely different directions. It is exciting to get to a point where there are obviously transitional characters between hominins and non-hominins. 

The other thing that is quite striking is that there is no obvious dividing line between being a quadruped and a biped and that the transition took some time and was gradual.  Don Johanson, in Lucy: The Beginnings of Humankind, word:

You don’t gradually go from being a quadruped to being a biped. What would the intermediate stage be–a triped? I’ve never seen one of these.

It appears that he may have been wrong, at least about the gradual part.

A New Species of Hominin Coeval With Lucy?

Great Googlymoogly! A new discovery has been made in the Afar triangle that indicates that a similar species of Australopithecus that was not A. afarensis lived alongside them. Science Daily writes:

“The Burtele partial foot clearly shows that at 3.4 million years ago, Lucy’s species, which walked upright on two legs, was not the only hominin species living in this region of Ethiopia,” said lead author and project leader Dr. Yohannes Haile-Selassie, curator of physical anthropology at The Cleveland Museum of Natural History. “Her species co-existed with close relatives who were more adept at climbing trees, like ‘Ardi’s’ species, Ardipithecus ramidus, which lived 4.4 million years ago.”

There is nothing to dictate that there were no intermediates between Ar. ramidus and Au. afarensis or that there were not several hominins on the landscape at this point. We know that there were two species of Ardipithecus. It is possible that this represents a descendent of Ar. ramidus or a descendent of a species that lived at the same time as Ardi and gave rise to a hominin that was more arboreal in nature. Until we have more to go on, it will be hard to construct any relationships that are even provisional.

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Did Competition Put Us On Our Feet?

Simply, yes. That is not earth-shattering. Cambridge News has a story on work done with chimpanzees that seems to confirm that behavioral alterations in higher level primates help with competitiveness. They write:

Anthropologists studying chimpanzees found the great apes, who usually walk on all fours, walk upright and free their hands for carrying when they need to grab more hard-to-find resources in one go, in the face of competition.

The team from the University of Cambridge and Kyoto University in Japan believe the benefit of “first come, first served” and getting a bigger share of scarce food supplies could, over a long period of time, have led some of our earliest “hominin” ancestors to evolve into “bipedal” primates walking on two legs permanently instead of four.

This has always been part of the bipedality model, that early hominins exploited the forest/fringe environment where they could get what they needed from the trees and from the savannas. The fact that Ardipithecus ramidus demonstrated bipedality in a forested environment sort of threw cold water on the more conservative of those models but it is also clear that even the level of bipedality continued to evolve over time and that, by the time later australopithecines had completely human, obligate bipedal locomotion, these hominins were living in the open and competing for those resources. It was at this point that our brains began to expand as well.

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The Role of Savannahs in Human Evolution

It now appears that grassland savannahs stretched further than originally thought during the critical time when human precursors became bipedal. As the Gence France Presse reports:

"There have been open habitats for all of the last six million years in the environments in eastern Africa where some of the most significant early human fossils were found," said Thure Cerling, a professor at the University of Utah and lead researcher of the study.

"Wherever we find human ancestors, we find evidence for open habitats similar to savannahs - much more open and savannah-like than forested," he said in a statement.

It still remains to be explained how Ardipithecus developed a bipedal gait within a forest environment, though.

Bernard Wood and Terry Harrison on Early Human Origins

Bernard Wood and Terry Harrison, two of the preeminent scholars in the study of human origins think that we are assimilating too many fossils into our family tree. In an article in PhysOrg, the author writes:

The paper, "The evolutionary context of the first hominins," reconsiders the evolutionary relationships of fossils named Orrorin, Sahelanthropus and Ardipithecus, dating from four to seven million years ago, which have been claimed to be the earliest human ancestors. Ardipithecus, commonly known as "Ardi," was discovered in Ethiopia and was found to be radically different from what many researchers had expected for an early human ancestor. Nonetheless, the scientists who made the discovery were adamant it is a human ancestor.

Wood and Harrison have a point here. One of the things that we castigate those that are unfamiliar with evolutionary theory about is “unilineal” thinking—that you can have transitional forms in the fossil record that do not reflect direct ancestry but “collateral” ancestry. This is especially true in the transition from the late theropod dinosaurs to birds. Yet, because we are talking about our own lineage, we tend to slip into a unileal way of thinking. Witness the brouhaha about Ida last year. Everyone wanted to roll her into the human fossil line even though there was no concrete evidence of such.

This does not mean that Sahelanthropus, Orrorin and Ardipithecus are not transitional. It just means that there is no direct evidence that they are ancestral to the human line. In the article, Wood and Harrison write:

There is no reason why higher primate evolution in Africa in the past ten million years should not mirror the complexity observed in the evolutionary histories of other mammals during the same time period. Nor is there any reason, especially with the lessons from Ramapithecus and Oreopithecus fresh in the minds of researchers, to assume that hominins should not be prone to the same limitations and uncertainties of phylogenetic analysis as other fossil primates.¹

This does not make them any less worthy of study or of producing excitement in the palaeoanthropological community.

¹Wood B., Harrison T. (2011) The evolutionary context of the first hominins. Nature 470:347-352.
10.1038/nature09709

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More Evidence For A Gradual Shift to Bipedalism

Discovery News has a story on work that is being done on early hominid locomotion. Jennifer Viegas writes:

Early human ancestors stopped swinging in trees and started walking on the ground sometime between 4.2 and 3.5 million years ago, according to a new study.

This key moment, when our ancestors became anatomically and behaviorally less ape-like, coincides with increased cooling, more defined seasonality, and a grassland growth spurt. All transformed former forest habitats into more varied ones, forcing our very early relatives to change their ways.

"With the trees being farther apart, it became energetically advantageous for hominids to cross the gaps bipedally," said Gabriele Macho, lead author of the study that was published in the latest issue of Folia Primatologica.

This follows on the heels (sorry) of the recent studies on Ardipithecus, where it was found that this hominid had a skeletal pattern that was adapted not just for the trees but for bipedal walking as well. How long was this pattern maintained? Viegas continues:

The scientists observed that the Australopithecus anamensis wrist bones exhibited pressure loads associated with modern arboreal animals. The analyzed Australopithecus afarensis bones conversely showed stress loads comparable to those of more terrestrial species, including modern humans.

The researchers concluded that the important shift in early hominid lifestyle happened around the time when A. afarensis first emerged.

A. anamensis is the form that followed, at least chronologically, Ardipithecus ramidus. Whether or not there is a direct ancestor/descendant relationship there, it is clear that the transitional elements in Ardipithecus were continued in the hominid line and that A. anamensis maintained a similar adaptation to the environment. The true changes in bipedalism and adaptation came with A. afarensis. This is yet another piece of the puzzle at this critical point in our history.

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BioLogos Post

The third BioLogos post, on the origins of bipedality and Ardipithecus, is up. Darrel actually changed the title a bit from “Bipedality—the Hallmark of Humanity” to just “Bipedality” to prevent a potential critical backlash. That is understandable.

As Darrel correctly pointed out, the hallmark of humanity is entrance into the Kingdom of God. It is important when reading the post that you keep this in your mind. That it looks like God took His time with us does not change that in any way. We are creations of God and His chosen creation. Let me know what you think.

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Ardipithecus Meets Modern Technology

The question of whether or how well Ardipithecus could walk has been hot since the discovery and description of the find were announced last year. Now a company that specializes in three-dimensional biomechanical reconstructions has taken an interest. According to the story in Send2Press:

LifeModeler, Inc. has reason to pay close attention. The company's LifeMOD™ biomechanical simulation software helped researchers understand how the 4.4 million-year-old Ardipithecus ramidus female walked and moved.

LifeModeler's founder, Shawn McGuan, worked with anthropologist C. Owen Lovejoy of Kent State University to create 3D models of the bones and muscles of this specimen first discovered in 1992.

Not only were they seeking information as to how her bones and muscles fit together, they also wanted to visualize the range of motion she was capable of, based on her anatomy. A detailed model of Ardi's foot provided particular insight for Lovejoy and the extensive team working on the project which was first disclosed last week in the journal Science.

The LifeMOD software determined that Ardi was the first fossil hominid to have had an opposable big toe, meaning she was able to live in the tree canopy and walk nearly upright on the ground. Research shows that a small bone inside a tendon maintained rigidity in her big toe.

Not exactly a nail in the coffin, but this will go a long way to establishing Ardipithecus as a real hominid. Much of the debate focused on the reconstruction of the pelvis and the foot anatomy was, for the most part, uncontroversial. More to come, I am sure.


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New 3.6 Million Year Old A. afarensis Remains

Science Daily reports that Yohannes Haile-Selassie's team in Ethiopia have found the remains of a 3.6 million year old Australopithecus afarensis individual that preserves enough of the post-cranium (below the head) to determine that bipedalism had completely taken hold of this species by this time. Of the individual, which is taller than Lucy (AL-288), he says this:

"As a result of this discovery, we can now confidently say that Lucy and her relatives were almost as proficient as we are walking on two legs, and that the elongation of our legs came earlier in our evolution than previously thought," he said in a statement. He explained, "

"All of our understanding of Australopithecus afarenis' locomotion was dependent on 'Lucy.' Because she was an exceptionally small female with absolutely short legs, this gave some researchers the impression that she was not fully adapted to upright walking. This new skeleton falsifies that impression because if 'Lucy's' frame had been as large as this specimen, her legs would also have been proportionally longer."

There is, thus, considerable variability in A. afarensis (this may yet revive the multiple species hypothesis that was put forth in the late 1970s about this material) This finding is expected, however, if the tracks at Laetoli are those of A. afarensis. We have good evidence that those are the tracks of a completely bipedal hominid.

If Ardipithecus ramidus ('Ardi') represents an ancestor to Australopithecus afarensis, then a considerable amount of evolution in bipedality occurred within 800 k years. A check of PNAS reveals that the paper is not out yet, but should be in a few days. Within the context of the debate concerning Ardipithecus' place on the fossil bush and the status of the reconstruction, it is important to remember what Owen Lovejoy wrote concerning Ardipithecus:

Ardipithecus ramidus now reveals that the early hominid evolutionary trajectory differed profoundly from those of our ape relatives from our clade’s very beginning. Ar. ramidus was already well-adapted to bipedality, even though it retained arboreal capabilities. Its postcranial anatomy reveals that locomotion in the chimpanzee/human last common ancestor (hereafter the CLCA) must have retained generalized above-branch quadrupedality, never relying sufficiently on suspension, vertical climbing, or knuckle walking to have elicited any musculoskeletal adaptations to these behaviors.

It is clear that, by 3.6 million years ago, those arboreal tendencies were gone. While it is still being debated whether or not Ardipithecus developed bipedality in the forest or in the forest fringe, the dessication of the landscape continued during the late Pliocene, and the remains of Kadanuumuu strongly suggest that early A. afarensis had completely adapted to this landscape.

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Casey Luskin on Ardipithecus

Casey Luskin thinks that Ardipithecus is "washed up." He writes:

In some ways, the career of a missing link mirrors the career of the celebutante. They break onto the scene with much fanfare and hype. Everyone is wowed—or at least, everyone pretends to be wowed so nobody can be accused of ruining the party. Besides, she’s useful for advancing lots of agendas. After a little while, people realize that the star doesn’t have all the talent everyone hoped for.

It is a little discouraging for a writer to use the phrase "missing link" when the idea has been so discredited for decades in the world of science. Palaeontologists have known for years that there is no such thing as a missing link. Recent phylogenetic systematic studies have further solidified this idea. Casey Luskin knows better. Onward. He continues:

Last fall “Ardi” came onto the missing link scene with a bang. The journal Science called her the “breakthrough of the year.” So did Time Magazine. We covered a few lone dissenters to the Ardi hype here on ENV.

But now Time Magazine is starting to go over apex of the hype curve. In an article titled, “ Ardi: The Human Ancestor Who Wasn't?,” Time notes, “Two new articles being published by Science question some of the major conclusions of Ardi's researchers, including whether this small, strange-looking creature is even a human ancestor at all.” Likewise, Nature reports, “Ardi may be more ape than human.”

White defends his analysis of Ardipithecus thus:

In an e-mail exchange with TIME, he says, "Dr. Sarmiento's views appear to be uniquely his own. Most notable in Dr. Sarmiento's comment is his refusal to recognize as significant the multiple and independently derived features of the Ardipithecus cranium, dentition, and postcranial skeleton. These features uniformly align this primate with all later hominids to the exclusion of any other ape — living or fossil. Has Dr. Sarmiento shown how the Ardipithecus evidence better fits his interpretation than the one we published? Not here."

White is not quite correct here. John Hawks also has similar misgivings, at least about the pelvis. He writes, in his blog:

During the seven months since I first detailed what I see as weak points in the pelvic description, I've become less and less persuaded that the pelvic features reflect any hominin-like locomotor adaptations in Ardipithecus. There are many unresolved functional issues, which obscure the phylogenetic relations between living and fossil apes. Ardi makes every tree less parsimonious, no matter which branch we put her on. Shoe-horning her into the hominins doesn't solve many problems, and creates some intractable ones.

I find myself calling her an ape.

Luskin, therefore, is not overstating his case. He concludes:

Discover Magazine is now saying "The bones of our ancestors do not speak across time with ultimate clarity." That's an understatement--but given how everyone previously fawned over Ardi's "missing link" status, could it be that there is more than mere science driving the promotion of these missing links?

This statement is neatly countered, however, by the last paragraph of the Time article:

While Sarmiento regards the hype around Ardi to have been overblown, Cerling says he still feels the discovery and re-creation of the ancient specimen to be a monumental breakthrough. But, he says, the science was in the evidence collected by White and colleagues, and not in their conclusions. "Many students will thoroughly examine the data and will come to their own independent evaluations," he says. In other words, science works a bit like evolution, and asking whether Ardi will survive as a major advancement is rather like going into the distant past and asking what the fate of her species would be: Only time will tell.

There is obviously considerable uncertainty in determining exactly what kind of ancestor Ardipithecus was to later hominids, if she was at all. As with every hominid species that has been discovered, only through painstaking analysis of the fossils will we be able to tell where she fits. I am reminded by the argument by Marcelin Boule that the Neandertal remains of La Chapelle-aux-Saints represented those of a pathological specimen of modern human. Given the wealth of Neandertal discoveries since then, we now know that Boule was wrong. It is still too early to tell if White and colleagues are right or wrong about Ardipithecus.

However, despite the fact that Ardipithecus may not be the hominid ancestor that we thought she was, she was at least an ape with derived characteristics toward the hominid line. While Ardipithecus may not have the "star power" we thought she would, she is a very important find, nevertheless.

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