April 13, 2011 | 11
MINNEAPOLIS—In August 2010 archaeologists announced that they had discovered evidence that pushed back the origin of butchery nearly 800,000 years. Studying bones of cow- and goat-size animals dated to around 3.4 million years ago from a site in Ethiopia called Dikika, Shannon McPherron of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his colleagues observed several distinctive marks. After conducting an extensive analysis of the marks, the team determined that they resulted from butchery with stone tools, although no implements were recovered at the site. Because the only human remains known from Dikika belong to Australopithecus afarensis—the species to which the famous Lucy fossil belongs—the researchers concluded A. afarensis was the butcher.
The discovery made a big splash, because scientists thought stone tool use and butchery originated with human ancestors more advanced than Lucy’s kind. Furthermore, according to conventional wisdom, A. afarensis relied primarily on plant foods.
Not everyone was convinced by the team’s claims. Last November, Manuel Domínguez-Rodrigo of the Complutense University of Madrid and his colleagues published a paper arguing on the basis of photographs of the Dikika specimens that the alleged cutmarks were actually the result of the bones being trampled by animals. Dikika team member Curtis Marean of Arizona State University fired back saying the critics had rushed to press without studying the actual remains, and that some of the telltale signs of butchery are only visible with firsthand inspection of the bones.
Here at the annual meeting of the Paleoanthropology Society on April 12, it was clear that the debate has only intensified since then. Jessica Thompson of the University of Queensland in Australia described the results of the Dikika team’s recent attempts to figure out whether the Dikika individuals used intentionally modified stone tools to deflesh the bones and access the marrow inside, or whether they used unmodified, naturally sharp-edged stones that they found in their environment to do the job.* The researchers removed meat and marrow from ungulate limb bones using modified and unmodified stones and then studied the resulting marks on the bones and compared them to the Dikika marks. They found that the Dikika marks all fall within the range of the damage that resulted in their experiment from butchery with naturally sharp-edged stones.
Dominguez-Rodrigo spoke next, giving a strongly worded talk reiterating his research group’s original assertions about the finds and admonishing the Dikika team for sidestepping scientific critique, misrepresenting the arguments of the critics, and insinuating that Dominguez-Rodrigo and his colleagues are biased against the notion of such ancient butchery. His group’s own experiments with unmodified stones to deflesh ungulate limbs indicate that it is possible to get marks that look like the Dikika ones, but he notes that the Dikika researchers were unable to show that the marks fall outside the range of variation of the trampling marks. They cannot prove that the marks are not the result of trampling, he insists.
UPDATE (4/17/11): Marean observes that only a small subset of the Dikika marks fall within the range of variation of Dominguez-Rodrigo’s trampled sample. The others fall outside that range of variation. "The odd leap in logic that they then make is that since a subset fall within the range of variation of the trampled sample, then it is best to assume that all are trample marks, even when those marks match stone-tool inflicted ones," he comments.
*Editor’s note (4/17/11): This sentence has been changed since it was first published to correct Thompson’s affiliation.
Image of Lucy skeleton, from Wikipedia