In a study to be published this week in the journal Science, researchers describe unearthing a "mother lode" of a half-dozen fossil primate species in southern China.
These primates eked out an existence just after the Eocene-Oligocene transition, some 34 million years ago. It was a time when drastic cooling made much of Asia inhospitable to primates, slashing their populations and rendering discoveries of such fossils especially rare.
"At the Eocene-Oligocene boundary, because of the rearrangement of Earth's major tectonic plates, you had a rapid drop in temperature and humidity," said K. Christopher Beard, senior curator at the University of Kansas' Biodiversity Institute and co-author of the report. "Primates like it warm and wet, so they faced hard times around the world -- to the extent that they went extinct in North America and Europe. Of course, primates somehow survived in Africa and Southern Asia, because we're still around to talk about it." Because anthropoid primates -- the forerunners of living monkeys, apes and humans-- first appeared in Asia, understanding their fate on that continent is key to grasping the arc of early primate and human evolution.
"This has always been an enigma," Beard said. "We had a lot of evidence previously that the earliest anthropoids originated in Asia. At some point, later in the Eocene, these Asian anthropoids got to Africa and started to diversify there. At some point, the geographic focal point of anthropoid evolution -- monkeys, apes and humans -- shifted from Asia to Africa. But we never understood when and why. Now, we know. The Eocene-Oligocene climate crisis virtually wiped out Asian anthropoids, so the only place they could evolve to become later monkeys, apes and humans was Africa."