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In a way, though, the evidence of butchery is the most exciting discovery of all. It tells us not just what our putative ancestors looked like but also how they behaved. According to the report published in Science, the fossil jawbone of an antelope exhibits "unambiguous cut marks made by a sharp stone flake," which the scientists believe was probably used to remove the animal's tongue. A three-toed horse had been dismembered and the meat on its leg bone filleted. The leg bone of yet another animal is scarred by man-made cuts, chop marks and signs of hammering, presumably to get at the marrow inside. And while slightly older tools were found previously at a site about 60 miles away, this is the earliest evidence associating tools with carnivory, an important milestone in human evolution and perhaps a factor in increasing brain size.
The tool marks don't necessarily imply that these creatures were hunters. While this harsh desert was far less arid 2.5 million years ago than it is today, it was still primarily grassland with little cover. "It was not a particularly friendly habitat for bipeds," says paleontologist Tim White of the University of California, Berkeley, who is co-leader of the expedition. Because it would not have been easy for the tool users to hide in ambush, White, like many other paleoanthropologists, believes that they were probably scavengers.
Most intriguing of all is the likelihood that the prehistoric butchers were able to plan far enough ahead to bring their tools with them. Says White: "Since we can't find any tools in the same geological layer as the animal bones, this technological equipment was probably carried in and then carried out." The case for this is made even stronger, he says, by the fact that there is no local source of raw materials for toolmaking.
Alas, there is no way to know at this point whether the three discoveries indicate a single transitional species or two or even three that lived at about the same time. Nor can the researchers tell what precise relationship any of these ancients might have to us. Hoping for some answers, White and his colleagues will head back to Ethiopia next fall.
--Reported by Andrea Dorfman/New York