for National Geographic News
Fossils of the most primitive primate ever discovered have been unearthed near Yellowstone National Park, a find that scientists say could redraw humans' family tree.
The animal belongs to an ancient group of mammals called plesiadapiforms, small creatures that scientists recently thought were closely related to modern nonprimates called flying lemurs.
But in a new study, the paleontologists who found the fossils say that plesiadapiforms are in fact the most primitive known primates.
The theory pushes the history of primate evolution back some ten million years.
Jonathan Bloch, a curator at the Florida Museum of Natural History, and graduate student Doug Boyer of New York's Stony Brook University discovered two 56-million-year-old fossils embedded in limestone in Wyoming's Bighorn Basin.
(See a map of Yellowstone National Park.)
One of the creatures, dubbed Dryomomys szalayi, is the most primitive known primate skeleton, the scientists say.
"Not only does it share many characteristics with other primitive primates, but it seems to also share characteristics with the most primitive living tree shrews [which are not primates]," Bloch said.
"That's exciting, because it's reflective of a shared, common ancestry," he said.
The finding suggests that plesiadapiforms evolved from ancient tree shrews and flying lemurs to become the first primitive primates.
It also suggests that humans' earliest ancestors lived in the trees, added study co-author Eric Sargis, a Yale University anthropologist.
"The first primates, you could say, looked quite a bit like arboreal tree shrews," Sargis added. "They were mixed feeders, eating fruit and insects and living in the trees."
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