The Overselling of Ardipithecus ramidusBy Casey Luskin If you believe what you read in the newsmedia, another new alleged missing link has been found. That is, if you consider something discovered in the early 1990’s new. This fossil seems to have spent almost as much time under the microscope at Berkeley as it did in the ground in Ethiopia, when it was first buried about 4.4 million years ago. Why did it take over 15 years for the reports on this fossil to finally be published, besides the fact that it allowed more time for planning the now-customary PR campaign? A 2002 article in Science explains exactly why: the bones were so brittle, “squished,” “chalky” and “erod[ed]” when cleaned such that many of the bone fragments had to be “reconstruct[ed]”—and that took a long time. Here’s the story from more than seven years ago: The next field season, team member Yohannes Haile-Selassie found the first of more than 100 fragments that make up about half of a single skeleton of this species, including a pelvis, leg, ankle and foot bones, wrist and hand bones, a lower jaw with teeth—and a skull. But in the past 8 years no details have been published on this skeleton. Why the delay? In part because the bones are so soft and crushed that preparing them requires a Herculean effort, says White. The skull is “squished,” he says, “and the bone is so chalky that when I clean an edge it erodes, so I have to mold every one of the broken pieces to reconstruct it.” The team hopes to publish in a year or so, and White claims that the skeleton is worth the wait, calling it a “phenomenal individual” that will be the “Rosetta stone for understanding bipedalism.” (Ann Gibbons, “In Search of the First Hominids,” Science, 295:1214-1219 (February 15, 2002).) (Michael D. Lemonick and Andrea Dorfman, "Excavating Ardi: A New Piece for the Puzzle of Human Evolution," Time Magazine (October 1, 2009).) (Ann Gibbons, "A New Kind of Ancestor: Ardipithecus Unveiled," Science, Vol. 326:36-40 (Oct. 2, 2009).) Claims of bipedalism often depend upon precise measurements of the angles of key bones such as the pelvis, femur, and knee-bones. But if these bones were discovered in such a crushed, squished, etc. form, determining the precise contours of these bones might become a highly subjective exercise. I’m sure they spent a lot of time on their reconstructions (and it certainly sounds like they did) but at the end of the day, it’s difficult to make solid claims about extremely unsolid bones. Skepticism about "Ardi's" Status as a Bipedal Ancestor of Modern Humans 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. In particular, A. ramidus casts doubt on the long-repeated hypothesis that humans evolved upright walking on the African Savannah where taller creatures had an advantage to see over tall grass by walking upright. A. ramidus walked upright in a “grassy woodland with patches of denser forest.” Time magazine’s article on A. ramidus explains the implications: (Michael D. Lemonick and Andrea Dorfman, "Excavating Ardi: A New Piece for the Puzzle of Human Evolution," Time Magazine (October 1, 2009).) There is one other option: A. ramidus wasn't bipedal. In fact, one Science article is reporting some serious scientific skepticism about A. ramidus being bipedal: (Ann Gibbons, "A New Kind of Ancestor: Ardipithecus Unveiled," Science, Vol. 326:36-40 (Oct. 2, 2009).) 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. Is "Ardi" All Washed Up? 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. Nobody wants to feign excitement anymore. Eventually, people are sickened of the original hype and become eager to see the celebutante fall. And then it's the fallen celebutante that starts making headlines. Substitute the word "missing link" for "celebutante" and this is something like what we're now seeing with "Ardi," the once-purported "oldest human ancestor." In 2009, "Ardi" came onto the missing link scene with a bang. The journal Science called her the "breakthrough of the year." So did Time Magazine. For a discussion of some of the few dissenters to the Ardi hype, see here. But Time Magazine has started to go over the apex of the hype curve. In a May, 2010 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." According to the Time article: "[White] showed no evidence that Ardi is on the human lineage," Sarmiento says. "Those characters that he posited as relating exclusively to humans also exist in apes and ape fossils that we consider not to be in the human lineage." The biggest mistake White made, according to the paper, was to use outdated characters and concepts to classify Ardi and to fail to identify anatomical clues that would rule her out as a human ancestor. As an example, Sarmiento says that on the base of Ardi's skull, the inside of the jaw joint surface is open as it is in orangutans and gibbons, and not fused to the rest of the skull as it is in humans and African apes -- suggesting that Ardi diverged before this character developed in the common ancestor of humans and apes. (Esteban E. Sarmiento, "Comment on the Paleobiology and Classification of Ardipithecus ramidus," Science, Vol. 328:1105 (May 28, 2010).) While these are relatively muted attacks on Ardi, they nonetheless show that the hype is wearing off. As Time notes, "Sarmiento regards the hype around Ardi to have been overblown." Given that these fossils come from the realm of science and not the world of celebrity gossip, why is the hype necessary in the first place? 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? |