Ardipithecus ramidus in Science Magazine

Science Magazine has a series of articles on the Ardipithecus ramidus remains that have been fully described. The articles are behind a subscription wall, so I cannot link to them. I will hit the high points, though. These quotes are necessarily short in order to conform to fair use guidelines. From Owen Lovejoy et al's Careful Climbing in the Miocene: The Forelimbs of Ardipithecus ramidus and Humans Are Primitive¹:

This discovery ends years of speculation about the course of human evolution. Our ancestors’ hands differed profoundly from those of living great apes, and therefore the two must have substantially differed in the ways they climbed, fed, and nested. It is African apes who have evolved so extensively since we shared our last common ancestor, not humans or our immediate hominid ancestors. Hands of the earliest hominids were less ape-like than ours and quite different from those of any living form.

From Combining Prehension and Propulsion: The Foot of Ardipithecus ramidus²:

One of the great advantages of our more rigid foot is that it works much better as a lever during upright walking and running (as it also does in monkeys). However, Ar. ramidus still had an opposable big toe, unlike any later hominid. Its ability to walk upright was therefore comparatively primitive. Because it had substantially modified the other four toes for upright walking, even while retaining its grasping big toe, the Ardipithecus foot was an odd mosaic that worked for both upright walking and climbing in trees. If our last common ancestor with the chimpanzee had not retained such an unspecialized foot, perhaps upright walking might never have evolved in the first place.

From The Pelvis and Femur of Ardipithecus ramidus: The Emergence of Upright Walking³

Ardipithecus ramidus now unveils how our skeleton became progressively modified for bipedality. Although the foot anatomy of Ar. ramidus shows that it was still climbing trees, on the ground it walked upright. Its pelvis is a mosaic that, although far from being chimpanzee-like, is still much more primitive than that of Australopithecus.

From The Great Divides: Ardipithecus ramidus Reveals the Postcrania of Our Last Common Ancestors with African Apes⁴:

The hominid descendant of the last common ancestor we shared with chimpanzees (the CLCA), Ardipithecus, became a biped by modifying its upper pelvis without abandoning its grasping big toe. It was therefore an unpredicted and odd mosaic. It appears, unlike Au. afarensis, to have occupied the basal adaptive plateau of hominid natural history. It is so rife with anatomical surprises that no one could have imagined it without direct fossil evidence.

The takeaway message here is that just as human evolution has proceeded by fits and spurts, the science behind it has done the same, like most other scientific endeavors. Five years ago, we were looking for an ancestor that looked something like a primitive chimpanzee. Now we know that is not how it went. The other cherished model that will go by the wayside is that bipedalism was an adaptation to the expansion of the savanna and grasslands and the retreat of the forests. The morphology of Ardipithecus seems, instead, to strongly suggest that bipedalism arose while our ancestors were still living in a forest environment. When the forest retreated, however, it is clear that Ardipithecus ramidus or something like it had the necessary adaptations to survive the changes and thrive in the new environment.

Some will say that because we were so wrong about our early hominid models, we don't know much about evolution. Those arguments have been put forth before. A cursory look at Marvin Lubenow's dreadful book Bones of Contention shows that. Ardipithecus doesn't tell us that human evolution didn't happen. It tells us that some of our models were wrong. In any scientific field, each new discovery ought to result in a slight rewrite of some cherished theories. If it doesn't, the science is stagnant. This is the critical difference between science and creationism. creationism cannot change its theories or models. It has only one explanation for how things happened, which must be correct. Any evidence that does not comport with those models must be explained away, no matter the cost to intellectual or scientific integrity. We found this out first-hand with the RATE project. The discovery of Ardipithecus ramidus should be fascinating and exciting to any evolutionary biologist. It not only shows us where we were wrong, it shows us what we got right and where our models need to be adjusted. More importantly, though, it shows us a glimpse of our deep past in an breathtakingly new and exciting way.

¹Lovejoy, C.O., Simpson, Scott, White, Tim, Asfaw, B, and Suwa, G. (2009) Careful Climbing in the Miocene: The Forelimbs of Ardipithecus ramidus and Humans Are Primitive. Science 326: 70

²Lovejoy, C, Latimer, B., Suwa, G., Asfaw, B., and White, T.D.(2009) Combining Prehension and Propulsion: The Foot of Ardipithecus ramidus. Science 326: 72

³Lovejoy, C., Suwa, G., Spurlock, L., Asfaw, B., White, T.D. (2009) The Pelvis and Femur of Ardipithecus ramidus: The Emergence of Upright Walking. Science 326: 71

⁴Lovejoy, C., Suwa, G., Simpson, Scott W., Matternes, Jay H., White, T.D. (2009) The Great Divides: Ardipithecus ramidus Reveals the Postcrania of Our Last Common Ancestors with African Apes. Science 326: 73

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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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Carl Weiland of CMI on Ardipithecus

Creation Ministries International's Carl Wieland, a long time member of the old guard of creationists, has an article on the site about Ardipithecus. He writes this:

Our writings in this ministry have already pointed out for years, referring to the detailed work of evolutionist anatomists such as Charles Oxnard, that there is a broad group of fossil creatures, now extinct, that is more dissimilar to both modern apes and modern humans than these are to each other. Oxnard’s conclusion was that australopithecines (the main constituents of this group) were not in the human line. We agree with him, not surprisingly. Ardipithecus appears to belong to this group as well; in fact, when the highly fragmented specimen was first discovered in the mid 1990s, it was originally put into that same genus, and called Australopithecus ramidus. Tim White, director of the Human Evolution Research Center at the University of California, Berkeley, says that Ardipithecus is not the common ancestor of apes and humans. But, he says, “it’s the closest we have ever been able to come”.

What is not being said here is that Mr. Wieland is still quoting the out-of-date Charles Oxnard paper about australopithecines, which was written before A. afarensis was described. Oxnard said, at the time (1975!) that although australopithecines were likely bipedal, they resembled apes more than humans. This paper was roundly criticized by many in the palaeoanthropological world because it relied on a very small set of measurements. Mr. Wieland is putting forth this evidence as if the last thirty-four years of palaeoanthropological research do not exist.

Tim White is perfectly correct about this. Ardipithecus shows us a creature that is closer to the split between humans and apes but, based on its morphology, is likely not at the split. Wieland continues to show his misunderstanding of evolution by continuing to rely on the outmoded unilineal, top-to-bottom ancestor tree idea that was abandoned by evolutionary biologists decades ago. He writes:

Did Ardi possess features which indicate a more upright stance than modern apes? Quite possibly, even likely. But then, so did the australopithecines/habilines. And both groups also possessed features making them suited for life in the trees as well. And CT scans of australopithecine skulls show that the organs of balance (the ‘semi-circular canals”) were positioned in ways quite different from that required for a creature that walks habitually upright.

In short, the significance of Ardi can be interpreted within either an evolutionary or creationist framework, and the latest analyses of these recycled bones and claims would appear to add no weight at all to the claims of either side. As cited elsewhere, a 1995 Nature article stated that it was “possible that Australopithecus [now Ardipithecus] ramidus is neither an ancestor of humanity, nor of chimpanzees … ”.¹ And indications are that nothing has really changed since then.

First off, let's be clear: Homo habilis had absolutely no specializations for living in the trees. In fact, by the time you get to Australopithecus africanus and A. robustus, those specializations are long gone. So, Wieland is completely wrong about this. He does, however, quote Henry Gee correctly. It is entirely possible that Ardipithecus ramidus was not a direct ancestor to the hominid forms that came later. This does not mean she is not transitional, nor does it mean she is unrelated to the hominids that came later. Once again, this goes to the heart of the difference between direct ancestry and collateral ancestry. One only needs to look at the diversity of australopithecines to see evidence of that. It is clear, based on the fossil record, that A. boisei became extinct somewhere around 1.2-1.5 gigayears ago. That doesn't mean that one of the other branches of australopithecines did not give rise to later hominids. It is clear that the hominids of Ardipithecus ramidus' time (be they only one species or many) were on a track to bipedality.

Ardipithecus shows us a window into an anthropological past before that of Lucy, where bipedalism has taken hold in at least one hominid species but was not fully developed. At one point, Wieland notes that this find is nothing new because the bones were discovered in 1994. What he does not say is that it took over ten years to painstakingly remove the bones from the surrounding matrix and reconstruct them. This is common for palaeoanthropological discoveries. What Wieland is calling ho-hum, is, in fact, a very exciting discovery.

¹Gee, H., Uprooting the human family tree, Nature 373(6509):15, 5 January 1995
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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

Casey Luskin and Ardipithecus

Much to my chagrin, I missed this a few weeks back, when Casey Luskin put up an article on the new Ardipithecus remains. Hyperbollically titled Artificially Reconstructed “Ardi” Overturns Prevailing Evolutionary Hypotheses of Human Evolution, Luskin writes:

The missing link presently being touted in the media, Ardipithecus ramidus, has had more reconstructive surgery than Michael Jackson. Assuming that their "extensive digital reconstruction" of its "badly crushed and distorted bones" is accurate, what does A. ramidus (or “Ardi” as the fawning media is affectionately calling it) really show us that we didn’t already know? We already knew of upright walking / tree-climbing, small-brained hominids—that’s what Lucy, an australopithecine, was. We already knew that there were australopithecine fossils dating back to before 4 million years, and this fossil is only a little bit older. So what does this fossil teach us? Assuming all the reconstructions of Ardi's crushed bones are objective and accurate, this fossil teaches us at least one very important thing: prevailing evolutionary explanations about how upright walking supposedly evolved in humans, confidently taught in countless college-level anthropology classes, were basically wrong.

The Ardipithecus remains were painstakingly reconstructed over a period of ten years, during which clues about her morphology were extracted. Mr. Luskin is not correct in his assertion that we already knew about australopithecine fossils before 4 gigayears ago. The earliest clear evidence that we had for bipedality dated to around 3.6 mya. It is clear that bipedality was established by that time but we didn't have anything before that. The description of the Ardipithecus remains tells us that bipedality was incipient 4.4 mya.

He is also wrong about what was being taught. It has never been clear how bipedality arose and there have been competing models to explain its development that have been nothing more than hypothetical because we didn't have anything to test them on. The most popular model was the "forest/fringe" model in which bipedality arose as the climate cooled and the savannas expanded. The precursors of the Gorillas and Chimpanzees adapted to the forest proper, while the baboons and their ilk took to the grasslands. That left the area in between where a hominid could develop that could take advantage of both. Guess what? That model turned out to be wrong. So what? Now we know that bipedality arose in a forested environment and our models can proceed from that knowledge. That is how science works. It learns from its mistakes.

Luskin is also wrong about what else it tells us. It tells us that this early biped was also completely adapted to the trees, and was, thus, in a position to take advantage of the shrinking forests when the dessication began around 4 mya. We still don't know exactly how bipedality developed, but we know that it did.

Luskin also writes:

It’s rarely discussed, but there are a number of upright-walking, forest-dwelling ape-like species known from prior to 10 million years ago that are thought to be far removed from human ancestors. This implies that bipedalism in a hominoid does not necessarily qualify an individual as a human ancestor, and it also casts doubt on classical explanations for the evolution of bipedalism.

WHAT???? Which ape-like species is he talking about? There are absolutely no bipedal apes of any kind in the Miocene prior to seven million years ago. If there had been, this would have been huge news! He, of course, cites no information here. It isn't rarely discussed. Its not discussed at all!! I have written Mr. Luskin and asked him which remains he is referring to. I know it ain't Dryopithecus, Sivapithecus, Oreopithecus, Kenyapithecus or Gigantopithecus.

Luskin, correctly, does point out that there is some skepticism in the palaeoanthropological community about whether the case for bipedality holds up, notably from Bill Jungers at Stony Brook and Bernard Wood, at GW, in Washington, D.C., although Wood states that the head has better evidence for bipedality. This is, perhaps, true and we do need to be cautious about hanging our hats on one specimen, but the evidence, as presented by White, Asfaw and Lovejoy, is compelling. Luskin concludes thus:

So what do we have with “Ardi”? We have an extremely crushed “Irish stew” fossil that has undergone extensive reconstruction in order to become part of a PR campaign to make bold claims of ancestral status to the human line, even though at base its qualities are very similar to previously known fossils, and there's a lot of skepticism about the claims being made. In other words, we have the typical media circus that we find every time a new "missing link" is found.

For one thing, Luskin has just finished saying our models are wrong. The only reason that our models are wrong is because Ardipithecus ramidus isn't similar to other previously known fossils. That is why it is generating the buzz. The remains are completely, radically, different from the fossils that we have that come after, when bipedality is firmly established. The only reason it became part of a PR campaign at all is because it was so unusual. Hundreds of fossils have been yanked out of the ground in the last decade, none of which made the front page because they confirmed what we had already suspected about human evolution. Ardipithecus ramidus didn't. It suggested new things to think about and new models to work from. That is how science proceeds. Casey Luskin doesn't seem to like that.

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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.

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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New ABC Article on Ardipithecus Draws Fire

A new ABC article by Russell Goldman on Ardipithecus appears to give credence to the arguments of creationists, who argue that the discovery is nothing more than an ape, a statement that is easy to dispense with but, for some reason, Goldman can't do. Goldman is a reporter who has had his share of accuracy complaints leveled at him. This appears to be more a problem with sensationalism than with acceptance of a clearly non-scientific position. He writes:

In one camp are evolutionary scientists who last week published and hailed the discovery of an upright walking ape named Ardipithecus ramidus, or "Ardi" for short, who made Ethiopia her home nearly 5 million years ago.

But despite the excitement from the paleontology community, another group of researchers, many of them with advanced degrees in science, are unimpressed by Ardi, who they believe is just another ape -- an ape of indeterminate age, they add, and an ape who cannot be an ancestor of modern man for a range of reasons, including one of singular importance: God created man in one day, and evolution is a fallacy.

This is highly misleading. Very few of the "researchers" have advanced degrees from universities where mainstream geology and palaeontology are taught or have degrees relevant to the study of palaeontology or geology. Most have published few to no articles in mainstream science journals and their positions on matters of astronomy, geology, biology and palaeontology are far outside the mainstream for all of these and other disciplines. Goldman continues:

"What creationists believe about human origins we get from the Bible," said David Menton an acclaimed anatomist and also a creationist. "The creation of the world takes place on page one of the Bible. If you throw out the first page of the Bible you might as well throw out the whole thing. If you can't live with the first page then pitch out the remaining thousand pages."

Quoting David Menton here is slightly unusual. He is the exception to the norm in creationist circles. Is he an acclaimed anatomist? Web of science lists 37 publications dating back some twenty years and he did teach at the Washington University School of Medicine, which is a mainstream university (he is now emeritus) but his expertise is the organization of cells, particularly the dermis and epidermis, rather than comparative anatomy. When he does mention the anatomical evidence, he is quoted as saying:

Menton said Ardi's skull and feet are exactly the kind of skull and feet you would expect an ape to have and have none of the features of modern humans.

"Evolutionists want to call Ardi 'ape-like.' This creature is ape-like, because she is an ape. Just call it an ape," he said.

The biggest problem Menton has with Ardi is her estimated age. The Earth, he says, is no more around 5,000 years old, a number creationists have estimated by counting the generations of man named in the Bible from Adam to Jesus.

"Evolution is supposedly based on science, but the science does not prove what they want it to. Creationism is not based on scientific observation but on God's word. God created everything in six days, and that's it."

Even eyeballing the evidence, I can tell that there are transitional traits and that the remains don't resemble an ape. This is not the first time a creationist has looked at a fossil human and proclaimed it to be an ape. On pages 112-113 of Of Pandas and People, Percival Davis and Dean Kenyon write:

Darwinists are convinced that Homo erectus was nearly human and directly ancestral to man. Design adherents, however, regard Homo erectus, as well as the other hominids discussed in this section, as little more than apes, and point instead to the abrupt appearance of the culture and patterns of behavior which distinguish man from the apes.¹

The first skull shown here is a chimpanzee skull. Below that is the Homo erectus skull from the Kenya National Museum found in East Rudolf, catalog number 3733





The anatomical differences are obvious and striking. Measurements have been taken on fossil material and compared to known apes. The results clearly indicate that Ardipithecus, Australopithecus, Homo habilis and Homo erectus specimens bear no resemblance whatever to apes. Regarding Ardipithecus, is Menton's grasp of anatomy that bad that he cannot tell the difference between an ape and a human, or is he just being dishonest?

It is nothing short of amazing that Goldman chooses to end his article with the quote from Menton. It completely refocuses the attention on the creationists and away from the importance of the fossil find. It also gives no room for rebuttal to his statements, quoting one of the discoverers, Owen Lovejoy, only once. Such treatment is irresponsible and offensive. The article should have ended with a comment on David Menton's quotes, which might read something like "Sadly, there are no mainstream geologists, astronomers, astrophysists, geochemists, geneticists, palaeontologists, palaeobotanists, or anthropologists that agree with Dr. Menton's position."

¹Davis, Percival, and Kenyon, Dean. (1993) Of Pandas and People: The Central Question of Biological Origins. Foundation for Thought and Ethics

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More on Ardipithecus ramidus

The NYT has a killer story by John Noble Wilford on the new Ardipithecus find (yes, I know, it is NYT but it was too good to pass up) with an associated graphic. It gives one an idea of just how transitional this find really is:

The Ardipithecus specimen, an adult female, probably stood four feet tall and weighed about 120 pounds, almost a foot taller and twice the weight of Lucy. Its brain was no larger than a modern chimp’s. It retained an agility for tree-climbing but already walked upright on two legs, a transforming innovation in hominids, though not as efficiently as Lucy’s kin.

Ardi’s feet had yet to develop the arch-like structure that came later with Lucy and on to humans. The hands were more like those of extinct apes. And its very long arms and short legs resembled the proportions of extinct apes, or even monkeys.

Here is the accompanying graphic, from the NYT.



Every so often, a find comes around and galvanizes the scientific world. This is one such find. A. afarensis is a good case for a transitional form. Ardipithecus ramidus is so much more. It also shows, in true evolutionary fashion, that the transition to bipedalism took place over a considerable period of time and happened in mosaic fashion.

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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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Smithsonian: Discovering Our Ancestors

The March issue of The Smithsonian Magazine has a large spread on the recent advances in human origins, including a large article on the discovery and identification of Ardipithecus ramidus by Ann Gibbons. One of the striking things about the find is the locale in which it took place: literally a palaeoanthropologist's dream come true. Gibbons writes:

As we wait for the Alisera to arrive, White explains that the team returns to this hostile spot year after year because it’s the only place in the world to yield fossils that span such a long stretch of human evolution, some six million years. In addition to Ardi, a possible direct ancestor, it is possible here to find hominid fossils from as recently as 160,000 years ago—an early Homo sapiens like us—all the way back to Ardipithecus kadabba, one of the earliest known hominids, who lived almost six million years ago. At last count, the Middle Awash project, which takes its name from this patch of the Afar desert and includes 70 scientists from 18 nations, has found 300 specimens from seven different hominid species that lived here one after the other.

It is the palaeoanthropological equivalent of the Liaoning shale fossil beds in China that have yielded so many dinosaur remains. Her description of what the remains of Ardipithecus represent is evocative:

One thing that is clear is that these early fossils belong in a class by themselves. These species did not look or act like other known apes or like Lucy and other members of Australopithecus. They were large-bodied ground dwellers that stood up and walked on two legs. But if you watched them move, you would not mistake them for Lucy’s species. They clung to life in the trees, but were poised to venture into more open country.

Becoming human, one slow step at a time. It is a pity that we do not have any more remains of Ardipithecus kadabba, which preceded A. ramidus by around a million years. What kind of individual would that be? Would he or she walk upright? Would we see any incipient hominid characteristics? At this point, quite literally, only God knows.
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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.”

Acts and Fiction: The ICR Tackles Australopithecus sediba

Brian Thomas of the ICR has a take on Australopthecus sediba in the recent news section of their web page. It doesn't start out well:

Evolution's search for the "missing link" between man and ape has a long and troubled history. Australopithecus sediba is the latest fossil find that is claimed to represent evolutionary human ancestors. But the remains of this extinct ape provide several solid clues that contradict any evolutionary relationship to man.

First, the remains were dated at 1.9 million years, which is at least one million years younger than evolutionary ages assigned to some fully human remains.1 If Au. sediba really were an ancestor to man, then its kind would have morphed into mankind and ought therefore not exist (as man's ancestor) after mankind had already arrived on the scene.2 Fossil ages from both species overlap considerably according to standard dates, thus failing to line up chronologically with an evolutionary scenario.

Well, first, evolution has never searched for the "missing link" of anything. There is no applicable concept in evolutionary biology for the concept since it is biologically meaningless. If Thomas has only read the popular press, he probably would have picked up on this term. It doesn't shows up in any of the Science papers on A. sediba, which one would hope Mr. Thomas has read.

The rest is just nonsense. He doesn't define what he means by "fully human." Therefore, one can only guess which hominids he is referring to. If he is referring to modern humans, he is 900 000 years off the mark. If he is referring to Homo erectus/ergaster, his timing is right but these remains aren't fully human by any stretch of the imagination. Even a cursory glance at these remains reveals this. It is therefore, not possible for A. sediba to "morph onto the scene" after the appearance of modern humans since even Homo erectus wasn't around at this point.

Additionally, how does the fact that the species overlap fail to "line up chronologically with an evolutionary scenario?" This is only true if one holds a strictly unilineal, vertical view of evolution, one that wasn't held even by Darwin. Such a view reflects a complete lack of either understanding or education in evolutionary theory by Mr. Thomas, suggesting he is not remotely qualified to write this essay.

He then completely misquotes Bill Jungers and his analysis of Ardipithecus. Thomas writes:

Just a few months ago, anthropologist C. Owen Lovejoy promoted Ardi as an ape who walked upright. But to William Jungers of Stony Brook University Medical Center--who, like the rest of the world, was only able to review the evidence after Ardi had already been proclaimed a walker in the publication of its initial study--the reconstructed skeleton "really doesn't show any adaptations for bipedalism at all."

What Jungers was actually quoted as saying was this:

None of the known foot components, no matter how well adapted to climbing, preclude Ardipithecus from walking upright on the ground. Jungers, however, thinks "it really doesn't show any adaptations for bipedalism at all." In fact, he says, many components of Ar. ramidus don't make Ardi look that much more adept at walking upright than chimpanzees—a primate that White et al. disavow as a model for early human evolution. In a summary paper led by Lovejoy, the authors describe Ardipithecus as a "facultative upright walker," one that can walk on two legs if needed (to carry something in the forearms, for example) but that isn't necessarily prone to do so. (emphasis mine)

Jungers wasn't talking about the skeletal reconstruction, he was talking about only the foot. He further indicates that, while he does not accept all of the evidence for bipedalism in Ardipithecus, he agrees that it would have been more bipedal than a chimpanzee.

Thomas then completely misreads the account of Berger's search for taphonomic data to understand how A. sediba died and to see if there is any residue of an endocast. Here is what Thomas writes:

For such soft samples as brains and insect eggs to have been preserved for thousands of years would be "special" enough, considering how quickly such organic materials decay. But to expect someone to believe that brain tissue escaped decay for 1.9 million years is asking far too much. It would be like expecting someone to believe that Au. sediba was man's ancestor--even though its skeleton was entirely ape-like and it supposedly lived long after its own descendants.

What Thomas doesn't seem to understand here is that Berger is looking for fossilized remains. Throughout hominid palaeoanthropological research, numerous brain endocasts have been found. In fact, one was recovered with the first australopithecine found, in 1924. Along with the face and a partial skull-cap, the fossilized brain of Australopithecus africanus was presented to Raymond Dart at the University of Witwatersrand. Immediately, he recognized that he was not looking at a run-of-the-mill primate but, rather, one that had human traits. This, and other discoveries, have led researchers to reconstruct how the brains of these early hominids differed from those of later ones. In fact, it has given rise to one of the most celebrated disagreements in palaeoanthropology, that between Dean Falk and Ralph Holloway, about just exactly how modern the brains of australopithecines were.

Thomas is completely unaware of this. Consequently, his comments are not just uninformed, they are ridiculous. The ICR's writers, once again, demonstrate that they are simply unwilling or unable to comprehend basic science.

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Ardipithecus ramidus: The Game Has Changed!

Wired (as well as a bunch of other sources) has a new article on the Ardipithecus ramidus find that has been analyzed. This find will change models of early human origins, for which there are actually more models than fossils. Don't misread that statement; there are plenty of fossils to reconstruct big chunks of our past but there are also some areas, particularly the early years, that are still sketchy. The article states:

“This is a landmark,” said Dean Falk, a University of Florida evolutionary anthropologist who reviewed the findings. “The field will go into a frenzy.”

Falk’s assessment was echoed by paleontologists around the world, who have waited for 15 years since a handful of 4.4 million-year-old fossils, belonging to an unknown hominid species, were found in sediments along the Awash River in Ethiopia.

Even then, the fossils were clearly special. The name of the species, chosen by paleontologist discoverers Tim White, Gen Suwa and Berhane Asfaw of the Middle Awash Project, means “root ground ape” in local dialect. The fossils likely “represent a long-sought potential root species for the Hominidae,” they wrote in a 1994 Nature paper (.pdf).

Conventional wisdom is that hominids arose due to a group of Miocene apes (Kenyapithecus?) adapting to the forest/fringe environment as environmental cooling created more savannas. These early hominids then moved to the savannas permanently around 3-3.5 mya. This find suggests that the evolution of bipedal, hominid behaviour may have taken place more in a forest environment than a savanna environment. Here is a revised tree from Wired, showing Ardipithecus, which is now assumed to be the root species in the hominid lineage.


The other takeaway message here is that the split between the precursors of chimpanzees and the precursors of gorillas is further back than we thought. Ardipithecus shows extremely derived characteristics relative to chimpanzees. In the world of human palaeontology, this is huge. It clearly shows a step between the quadrupedal apes of the Miocene and the demonstratively bipedal australopithecines of the Plio-Pleistocene. Folks, this is as transitional as it gets.

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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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Owen Lovejoy on Ardipithecus ramidus

Owen Lovejoy, one of the leading scholars on all things australopithecine and one of the principle describers of the new Ardipithecus finds, describes the importance of the find in terms of our understanding of human/ape relationships. In Breitbart.com, he says:

"People often think we evolved from apes, but no, apes in many ways evolved from us," Lovejoy said. "It has been a popular idea to think humans are modified chimpanzees. From studying Ardipithecus ramidus, or 'Ardi,' we learn that we cannot understand or model human evolution from chimps and gorillas."

Lovejoy (and others) are arguing that the human/ape split came about long before the modern great apes arose and, thus, we share no behavioral or morphological traits in common. If the split between apes and humans was between eight and nine million years ago, that would mean eight million years of evolution for apes to become what they are today. That's a lot of time.

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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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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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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