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Tuesday, October 14, 2008

Early humans cross the wet Sahara, and bonobos make war as well as love

It's science time again!

Today my partner on Science's anthropology beat, Ann Gibbons, and I pull a double whammy with two important stories on our online news service, ScienceNOW. Mine, entitled "Out of Africa, Across a Wet Sahara," is at this link, and Ann's, "An Ape Shows Its Killer Instincts," is at this link. Both links are free for 4 weeks from today.

Mine starts out as follows:

Modern humans arose in sub-Saharan Africa as early as 200,000 years ago, but our species did not venture beyond Africa until at least 80,000 years later. Just why they took so long to travel north is not clear, but many researchers have suggested that the bone-dry Sahara Desert was a major barrier to migrations from the south. Yet a new study indicates that the Sahara was crossed by wide rivers during a wet period that began about 120,000 years ago, providing a hospitable corridor for humans on the move.

Ann's story begins:

Bonobos have a reputation as the hippies of the primate world, with a make-love-not-war image. But scientists appear to have underestimated their bloodthirsty tendencies. In a new study, researchers report observing wild bonobos hunting and eating monkeys, which shows that the apes are not so different from their more aggressive cousins, the common chimpanzees.

Be sure to click the links for more details. The human and chimp evolutionary lines split sometime between 5-7 million years ago, and the bonobos split from the so-called common chimps several million years later. But there may be no way of getting around the fact that violent behavior is part of the evolutionary heritage of all three species of apes. Bonobos do seem better at controlling those impulses than chimpanzees, however, and we humans are fully capable of doing so as well--that is, when we really want to.

The map shows river channels across the Sahara some 120,000 years ago. Credit: Anne Osborne, University of Bristol

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