Father of Us All?

In life, the creature probably resembled a chimpanzee more than anything else. It moved through a lakeside landscape of grasslands and forest searching for food, accompanied by small bands of its fellows, most likely, and keeping a sharp eye out for pythons, crocodiles and saber-toothed cats. This animal probably shared the forest with apes and monkeys and, like them, spent some time up in the trees. It may have walked upright, which apes rarely do for very long at a stretch. But at a casual glance, it would have seemed to our eyes like just another chimp.

In death, however, this creature has just sent shock waves through the world of science. After eight grueling years of hunting in the hot, wind-scoured desert of central Africa, an international team of researchers has uncovered one of the most sensational fossil finds in living memory: the well-preserved skull of a chimp-size animal, probably a male, that doesn't fit any known species. According to paleontologist Michel Brunet of the University of Poitiers in France, whose team reported the find in Nature last week, there is no way it could have been an ape of any kind. It was almost certainly a hominid--a member of a subdivision of the primate family whose only living representative is modern man. And it has left scientists gasping with astonishment for several reasons.

To start with, it is nearly 7 million years old--a million years more ancient than the previous record holder. Indeed, this new species is as much older than the famous Lucy as Lucy is older than we are. It almost certainly dates from very near that crucial moment in prehistory when hominids began to tread an evolutionary path that diverged from that of chimps, our closest living relatives. Even more surprising, this ancient hominid was not discovered anywhere near the Great Rift Valley of East Africa, where all the record setters of the past three decades have been found. Instead, it turned up in the sub-Saharan Sahel region of Chad, more than 1,500 miles to the west, forcing a rethinking of the conventional wisdom about where humans arose.

Beyond that, the animal's habitat may cast further doubt on the already beleaguered notion that our ancestors first emerged on a treeless savanna. It now looks as though this pivotal event happened in a setting that was at least partly wooded. Most remarkable of all, though, is the skull itself. The creature, known formally as Sahelanthropus tchadensis (roughly translated "Sahel hominid from Chad") and informally as Toumai ("hope of life," in the local Goran language), has a mix of apelike and hominid features. And to some paleontologists, the hominid features, especially the face, are a lot more modern-looking than anyone would have expected at so early an evolutionary stage. "A hominid of this age," writes Bernard Wood of George Washington University, in a commentary accompanying the Nature articles, "...should certainly not have the face of a hominid less than one-third of its geological age."