A WEE SURPRISE

“The problem with the fossil record,” NIU anthropology professor Daniel Gebo says, “is that every time you find a new link, there’s always a gap above and below it.”

In the study of distant human evolution, one such major gap existed between lower and higher primates, where Gebo’s research is focused. Primates are distinguished from other mammals by their larger brains, grasping hands and feet, and the position of their eyes, located in the front of the skull. The fossil record shows primates took to the trees at least 55 million years ago. At some point, lower primates went their separate way, developing into today’s lemurs, lorises, bush babies, and tarsiers. Meanwhile, higher primates branched into a lineage that includes monkeys, apes, and humans.

In the spring 2000, Gebo announced the startling find of 45 million-year-old ankle-bones, each the size of a grain of rice, belonging to separate thumb-length primates. The wee creatures weighed well under an ounce and probably made a nice midnight snack for hungry owls.

 

Dan Gebo

NIU anthropology professor Daniel Gebo recently announced the startling find of 45 million-year-old anklebones, each the size of a grain of rice, belonging to separate thumb-length primates. The wee creatures weighed well under an ounce and probably made a nice midnight snack for hungry owls.

“The problem with the fossil record,” NIU anthropology professor Daniel Gebo says, “is that every time you find a new link, there’s always a gap above and below it.”

In the study of distant human evolution, one such major gap existed between lower and higher primates, where Gebo’s research is focused. Primates are distinguished from other mammals by their larger brains, grasping hands and feet, and the position of their eyes, located in the front of the skull. The fossil record shows primates took to the trees at least 55 million years ago. At some point, lower primates went their separate way, developing into today’s lemurs, lorises, bush babies, and tarsiers. Meanwhile, higher primates branched into a lineage that includes monkeys, apes, and humans.

In the spring 2000, Gebo announced the startling find of 45 million-year-old ankle-bones, each the size of a grain of rice, belonging to separate thumb-length primates. The wee creatures weighed well under an ounce and probably made a nice midnight snack for hungry owls.

Gebo and colleagues recovered the fossils from a Chinese commercial limestone quarry about 100 miles west of Shanghai. In one of the creatures, known as Eosimias, the researchers found evidence of both lower and higher primate characteristics.

“We had the first unambiguous evidence bridging the anatomical gap between lower and higher primates,” Gebo says. “The thing that surprised all of us was the diminutive size, because most higher primates are fairly large. Finding a species weighing a third to a half of an ounce was just out of the realm of possibility for a lot of people.”

Since the creatures, and likewise their brains, were so small, any adaptive advantage toward intelligence would have been lost. That’s important, Gebo adds, because it indicates the beginnings of the huge radiation we know as higher primates probably had nothing to do with the creatures’ intelligence.

The human line among higher primates would split off many millions of years later and on a different continent. “Under the skin,” Gebo says, “we’re all African.”

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