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This means we need a better explanation of why and how chimps and humans went their separate evolutionary ways, McBrearty says. The discovery that chimps were living in semi-arid conditions as well as in the jungle seems to blow apart the simplistic idea that it was the shift to savannah that led to humans walking upright.

Ummm, no, of its own accord, it doesn't. The chimp fossils are from 500,000 years ago. The human & chimp lineages split some 6 million years ago. The chimps had several million years to enter the area where humans (and their ancestors) may very well have been alone beforehand. That would certainly explain why no older chimp fossils have been found as well.

[AntiGuv]

PS. And if these researchers did indeed say that this "seems to blow apart the simplistic idea" blah, blah, blah then they are deeply incompetent, even despite their intriguing discovery.