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Fossil discovery complicates Homo sapiens' family tree (+video)

A team led by renowned paleoanthropologist Meave Leakey has discovered new fossils that they say suggests that our apelike ancestors shared their habitat with other hominid species. 

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But it's not that simple. The Leakey scientific team contends that other fossils of old hominids — not those cited in their new study — don't seem to match either erectus or 1470. They argue that the other fossils seem to have smaller heads and not just because they are female. For that reason, the Leakeys believe there were three living Homo species between 1.8 millionand 2 million years ago. They would be Homo erectus, the 1470 species, and a third branch.

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"Anyway you cut it there are three species," study co-author Susan Anton, an anthropologist at New York University. "One of them is named erectus and that ultimately in our opinion is going to lead to us."

Both of the species that Meave Leakey said existed back then went extinct more than a million years ago in evolutionary dead-ends.

"Human evolution is clearly not the straight line that it once was," Spoor said.

The three different species could have been living at the same time at the same place, but probably didn't interact much, he said. Still, he said, East Africa nearly 2 million years ago "was quite a crowded place."

And making matters somewhat more confusing, the Leakeys and Spoor refused to give names to the two non-erectus speciesor attach them to some of the other Homo species names that are in scientific literature but still disputed. That's because of confusion about what species belongs where, Anton said.

Two likely possibilities are Homo rudolfensis —which is where 1470 and its kin seem to belong — and Homo habilis, where the other non-erectus belong, Anton said. The team said the new fossils mean scientists can reclassify those categorized as non-erectus species and confirm the earlier but disputed Leakey claim.

But Tim White, a prominent evolutionary biologist at the University of California Berkeley, is not buying this new species idea, nor is Milford Wolpoff, a longtime professor of anthropology at the University of Michigan. They said the Leakeys are making too big a jump from too little evidence.

White said it's similar to someone looking at the jaw of a female gymnast in the Olympics, the jaw of a male shot-putter, ignoring the faces in the crowd and deciding the shot-putter and gymnast have to be a different species.

Eric Delson, a paleoanthropology professor at Lehman College in New York, said he buys the Leakeys' study, but added: "There's no question that it's not definite." He said it won't convince doubters until fossils of both sexes of both non- erectusspecies are found.

"It's a messy time period," Delson said.

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