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After more than a decade of digging, researchers working in Chad have made the fossil discovery of a lifetime: a nearly complete skull of the oldest and most primitive member of the human family yet known. Nicknamed Touma¿¿or "hope of life" in the local Goran language¿it belongs to an entirely new genus and species of hominid, Sahelanthropus tchadensis. And at almost seven million years old, it has taken scientists several crucial steps closer to the point in time at which humans and chimpanzees diverged. Yet as is the case for most spectacular finds, this one raises as many questions, if not more, than it answers.
For one, until now almost all of the next earliest hominid fossils unearthed so far have come from East Africa, leading some scholars to posit that the origin of humans was essentially an "East Side story." Touma¿, however, comes from central Africa. And then there¿s his (the skull is thought to be that of a male) surprising combination of primitive and advanced features. Characteristics of the face and teeth clearly align Touma¿ with hominids, say team leader Michel Brunet of the University of Poitiers in France and his colleagues. But the braincase is comparable in size to that of a small ape. (Whether or not Touma¿ and his kind were bipedal remains a matter of uncertainty. No skeletal elements have been found, but features on the base of the skull and the face resemble those of known bipedal hominids.)
As the oldest hominid on record, S. tchadensis could be the ancestor of all later hominids¿including us¿according to Brunet and his collaborators, who announced their discovery today in the journal Nature. But that will be difficult to prove, cautions Bernard Wood of George Washington University in an accompanying commentary. "My prediction is that S. tchadensis is just the tip of an iceberg of taxonomic diversity during hominid evolution 5-7 million years ago," he writes. Whatever the case, it seems certain that this find will have a tremendous impact on the study of human origins. "It¿s a lot of emotion to have in my hand the beginning of the human lineage," Brunet muses. "I have been looking for this for so long."
