The discovery of a nearly 7-million-year-old skull has been hailed as "a small nuclear bomb" for evolution, "the most important fossil discovery in living memory," and a "challenge to human origins." Time said that the fossil might be "your very first relative."

An international team of scientists uncovered the mostly intact cranium—nicknamed Toumai (meaning "hope of life")—along with two jawbone fragments and several teeth in Chad's Djurab desert last summer. Some paleontologists say the find, announced in the July issue of Nature, rewrites the map of human evolution.

Under previous evolution theories, the new species, Sahelanthropus tchadensis, is too advanced for its age. Its presence at that period of time, advocates say, does not jibe with evolution's traditionally straight line of gradually developing species of primates (called hominids) who eventually became homo sapiens. This discovery (coupled with earlier ones) has led some scientists to argue that the human family tree is actually a bush with various species branching out to different types of life or to dead ends.

Toumai's combination of ape and hominid qualities blurs the commonly held timeline, which portrays a world of abundant apes around 10 million years ago with the first hominids showing up about five million years later.

According to scientists, Toumai looks like a chimpanzee from the back but has human features in front: an ape with a flat human face. Though a million years older than any other hominid, some of the skull's attributes are considered to be more human-like than 3-million-year-old hominid skulls. It has a thick gorilla-like brow, a chimpanzee-type brain cage, and human-like teeth. The opening for the spinal cord suggests it might have walked ...

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