Doubts About Toumai

  Did paleontology just fill in a gap in the human family tree? That's what you'd think from reading the headlines this month. "A fossil unearthed in Africa pushes back human origins," reported The New York Times on page one. But, as is often the case with scientific discoveries relating to the theory of evolution, you've got to read more than just the headlines. The details point to a much less triumphalistic picture. The new fossils, unearthed by a French team in Chad, included a nearly complete skull, which has been dubbed "Toumai." Dated at between six and seven million years old, Toumai has been given the formal scientific name Sahelanthropus, after the harsh Sahel Desert where the fossil was found. Sahelanthropus has been classified as an entirely new genus of primate -- something scientists do only when those fossils have features that don't fit into any existing group. That's where the Toumai puzzle begins. Paleontology is an interpretative science. Fragmentary fossil remains don't announce what species they are or their lineage. Paleontologists have to figure that out, if they can. Since nearly all fossil groups are extinct, there's plenty of room for disagreement about the correct interpretation. And that's exactly what happened with Toumai. No sooner was the discovery announced than another French paleontologist, Dr. Brigitte Senut of the National History Museum in Paris, said that she doubted any link to humans. The features of the skull that the Toumai team had interpreted "hominid," Senut claimed, would be better explained if the skull actually came from an extinct species of gorilla. Toumai had a short face and small canine teeth, and Senut thinks that these are the characteristics "of the skull of a female gorilla," not a human ancestor. On hearing of Senut's dissenting interpretation, the Toumai team called a news conference to denounce her view. Such strong disagreements mark the history of paleoanthropology. It's an enterprise where leading researchers have had long-running feuds with each other, and where conflicting scenarios for human evolution come and go with remarkable frequency. Why the conflict? Well, think of the fossils themselves as bricks -- the building materials for a scientific theory. These bricks are, however, too few in number and, in most cases, poorly preserved. Nevertheless, evolutionary paleoanthropologists want to make a building out of them, the story of human evolution. So they patch the bricks together with a lot of mortar of their own making. With Toumai, for instance, anthropologist Bernard Wood of George Washington University said that the discovery may show many other fossil hominids are not human ancestors at all. Wood locates Toumai in evolutionary history by ripping out the theoretical mortar others have used in the past and adding some of his own. What's a thoughtful onlooker to conclude? That the fossils are real, but their interpretation is very much up for grabs. The theories of relationships between extinct groups have short lives. Keep that in mind next time you read the science headlines, or your neighbor tells you scientists have found the "missing link" -- not so. It's pure conjecture, nothing more. For further reading and information: Daniel Lieberman, "Upending the Expectations of Science," The New York Times, 14 July 2002. Free registration required. (This piece by Lieberman, an anthropologist at Harvard, is especially good, as he points out how the discovery of Toumai overturns accepted evolutionary theories.) http://www.nytimes.com/2002/07/14/opinion/14LIEB.html Claude Canellas, "Man or Gorilla?: Experts at Odds over Ancient Skull," Reuters, 12 July 2002. (Original story on Brigitte Senut's differing interpretation.) http://www.reuters.com/news_article.jhtml?type=search&StoryID=1196368 Bernard Wood, "Palaeoanthropology: Hominid Revelations from Chad," Nature 418, (11 July 2002): 133-35. http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v418/n6894/full/418133a_fs.html Jimmy Davis and Harry Poe, Designer Universe: Intelligent Design and the Existence of God (Broadman and Holman, 2002). http://www.pfmonline.net/products.taf?_function=d&IC=BKDSU Charles Colson and Nancy Pearcey, Developing a Christian Worldview of Science and Evolution (Tyndale, 1999). http://www.pfmonline.net/products.taf?_function=d&IC=BKSAE Learn more about evolution and intelligent design by visiting the Discovery Institute's website. http://www.discovery.org

07/29/02