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For decades scientists have worked to connect the dots between dozens of fossil discoveries in East and southern Africa in hopes of constructing an accurate picture of human origins. Now, a new find in western Central Africa suggests the picture may be radically different than widely assumed.
A team of researchers excavating in northern Chad has unearthed the well-preserved skull and other fossilized remains of what they believe was a previously unknown hominid, or early human precursor, that lived six to seven million years ago. That date would make it the oldest known ancestor of humans.
The finding has excited the scientific community especially because it opens a window onto a period near the time when humans and apes diverged from a common ancestor. Virtually nothing about that period is known, as most human fossils are considerably younger.
Various aspects of the new fossils could force scientists to rethink some basic theories about human origins, according to several scientists who were not part of the research team.
In a statement issued by Nature, which reported the discovery in its July 11 issue, anthropology professor Daniel Lieberman of Harvard University said the new find "will have the impact of a small nuclear bomb."
"One of the most important things this skull tells us is how much we don't know," he said in a phone interview. "It suggests how diverse hominids might have been in Africa, and shows that lots of things were going on in Africa that we can't imagine."
Lieberman saw the skull and, like some other observers, said he was particularly intrigued by the creature's unusual mix of both primitive and advanced traits. The braincase is chimp-like, for example, but the face, teeth, and somewhat flattened head resemble those of humans.
"What's most astonishing is that the facial features are like those that we don't see until 1.8 million years ago in the genus Homo. It is more Homo than australopithecine," he said, referring to the best-known group of hominids, which appeared in East Africa three to four million years ago and whose fossils have provided most of what we know about the earliest human ancestors.
So, is the new skull fossil a hominid—perhaps our earliest known ancestor?
"It's very hard to be sure, but I think it's a hominid," said Lieberman. "But whether it was the earliest hominid or the earliest ancestor of anyone living today, we can't tell."
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