Monday, October 19, 2009

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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4 comments:

  1. I have written Mr. Luskin and asked him which remains he is referring to.

    I look forward to Casey's response.

    ReplyDelete
  2. He wrote back. Time to parse it.

    ReplyDelete
  3. Funny video: Darwin serenades Ardi "My Funny Hominid"...he bags on creationists too
    http://02e56fa.netsolhost.com/blog1/index.php/2009/10/22/darwin-serenades-ardi-my-funny-hominid-a

    ReplyDelete