Planet Earth

Human Origins


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9. Early Humans Had Tiny Brains Anthropologists and paleontologists have long thought that the schlep from Africa to Europe roughly 800,000 years ago required a certain amount of smarts and a handful of relatively complex tools. But last July, a team of archaeologists excavated the third of three skulls found in the Republic of Georgia that prove human ancestors needn't have been particularly bright or technologically savvy to make the journey north. The skulls are about 1.8 million years old, putting the move out of Africa nearly a million years earlier than researchers had previously guessed. Most interesting, the cranial capacity of these hominids is minuscule. The newest of the trio has a braincase of 37 cubic inches—less than half of what we've got. Rudimentary tools found nearby add to the evidence that these primates weren't too advanced. "We have thousands of stone tools," says David Lordkipanidze, deputy director of the Georgian State Museum at Tbilisi, who led the team. "They're very simple— just choppers produced from local material."

The first two skulls were pegged as Homo erectus, and the new one is similar enough to get the same label, if only tentatively. Its face, teeth, and cranium size make it look more like Homo habilis, our more distant ancestor. It may be primitive, but it's still a hominid. "It could be something intermediate— between H. habilis and H. erectus," says Lordkipanidze. "It could even be one of the earliest Homos in the world." If that's true, then H. erectus may have evolved in Eurasia, an idea rarely entertained.

The site may give us the first glimpse of how our predecessors lived—it's the only place where early hominids have surfaced in a group. Although nothing like living quarters have turned up yet, the three were clearly living by a lakeshore. Also, the new skull is so well preserved, it may have been buried with great care soon after death. More clues are inevitable. "We've excavated only 5 percent of the whole site," says Lordkipanidze. "We are on the way to finding a whole population." — Michael Abrams

63. Earlier Date Set For Human Intelligence

Some scratched-up chunks of ocher, found in a cave in South Africa, may signal a change in assumptions about just how long ago humans began to communicate abstract thoughts through language and art.

Archaeologists dating Paleolithic cave paintings in France thought such behavior arose suddenly about 35,000 years ago in Europe with Cro-Magnon man. However, this year archaeologist Christopher Henshilwood of the African Heritage Research Institute in Cape Town uncovered what he considers much earlier evidence of abstract thought—two pieces of ocher engraved by a South African cave dweller 77,000 years ago.

The ocher artifacts were found in Blombos Cave, on a remote stretch of Indian Ocean coast. They may not merit the coffee-table-book treatment accorded the artful cave paintings at Lascaux, but they are distinctively human. The first bears a series of lines and hash marks, like a prisoner's count of his days in captivity. The second is crosshatched to form a series of regular triangles. Microscopic examinations have shown that the lines were carved in stages, first in one direction and then another. "These are deliberate engravings," says Henshilwood. "Someone sat down and made these lines in a consecutive fashion to produce some kind of abstract design."

Henshilwood won't hazard a guess as to what the markings mean. "I've had hundreds of e-mails suggesting what they would be," he laughs, "ranging from a map indicating the way to Polynesia to trusses for a bridge." Others have argued that the engravings are not abstract representations at all but merely the meaningless markings of a bored toolmaker, absentmindedly scratching at a piece of ocher. While Henshilwood rejects that suggestion, he ran the idea past some colleagues who thought it an even better indication of abstract thought—as only modern people would sit and doodle. — Shanti Menon

39. Surprise: Humans Celebrate 7 Millionth Birthday

Hominids get older as the years go by. This year, it seems, we've turned 7 million, or at least that's the suggestion made by a skull unearthed in the Djourab Desert in Chad. The ancient skull is butting up against theories of human evolution because of its incredible antiquity and unexpected human features.

A group of geologists, sedimentologists, paleontologists, and anthropologists reported the find last July. "The main thing in this discovery is the age," says Michel Brunet, a paleoanthropologist at the University of Poitiers in France who led the team. The specimen itself—a nearly complete skull, two portions of the jaw, and a handful of teeth—can't be dated directly because it wasn't found in the kind of sediment that allows radioactive dating; however, Brunet was able to come up with an age by comparing the bones with those found at similar sites in Kenya and Ethiopia.

The fossil's humanlike face and teeth and chimp-size cranium are so different from any other known hominid that Brunet and his team have denominated it a new species: Sahelanthropus tchadensis. The French team nicknamed the fellow Toumaï; in Goran, the language local to the site, the word means "hope of life." The hybrid of familiar face and tiny brain means Toumaï probably lived just after the time when chimps and hominids were going their separate ways. "My colleagues once thought that chimpanzees and humans diverged around 5 million or 6 million years ago," says Brunet. "But with Toumaï, it's quite clear that the divergence is older— at least 7 million years, and maybe a little bit more." The evidence that he was more hominid than ape can be found in the details. The area behind the skull's thick brow ridge (which suggests it was a male) is relatively flat. "In apes, chimps, and gorillas, you have a big depression just behind this brow ridge," says Brunet. "It's quite clear that the Toumaï cranium is completely different." Toumaï's small canines are further proof that he was more like us than an ape.

The famous 3-million-year-old Lucy, a.k.a. Australopithecus afarensis, had a larger cranium than Toumaï but a much more chimplike face. Evolution doesn't usually reverse itself, so it's unlikely that we evolved from a chimp face to a human face to a chimp face and then back to human again. The implication of this find is that many different species of hominid have walked the earth—and so our story may be more complex than previously imagined. — Michael Abrams

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