Tuesday, April 20, 2010

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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  1. Thanks for writing on this. I have been interested in the au. sediba find since its unveiling. It is very helpful for a non-scientist like myself to read your critiques of YEC and ID material. Please keep it up. Also, it is good to see that you put a post on BioLogos. They need a voice from the paleoanthropology field, so I hope you continue working with them.

    A question: When you say, "Thomas then completely misreads the account of Berger's search for taphonomic data to understand how Ardipithecus died and to see if there is any residue of an endocast," do you mean au. sediba rather than Ardipithecus?

  2. I did, in fact, mean A. sediba. Thanks for the catch. I will correct the entry. Thank you for the kind words. I hope to have a long and fruitful relationship with Biologos.