Asian fossils reveal primate evolution.

Paleontologists would always like more time in the field, but K. Christopher Beard is really racing against the clock. In 2 years, a new dam will flood his field site along China's Yellow River, a location harboring secrets of the early evolution of anthropoids, the group of higher primates that includes monkeys, apes, and humans.

While working in central China's Yuanqu basin last May, Beard and his colleagues unearthed important new fossils of a small mammal called Eosimias. The finds demonstrate that Eosimias was an anthropoid and not a hedgehog, as some critics had once argued, Beard reported last week at the annual meeting of the Society of Vertebrate Paleontology in Pittsburgh.

"Eosimias is the earliest well-known fossil anthropoid, and it's also important because it is so primitive that it really is the only good evidence we have of what early anthropoids would have looked like," says Beard, a researcher at the Carnegie Museum of Natural History in Pittsburgh.

Carnegie scientists and Chinese coworkers first identified Eosimias last year from two partial jaws and four teeth, all found in 45- million-year-old rocks in eastern China (SN: 4/16/94, p.245). This year, in the slightly younger rocks of the Yuanqu basin, they unearthed a complete lower jaw, with all its teeth in place, belonging to another species within the Eosimias genus.

Tiny in comparison to living simians, the mouse-size Chinese animal displayed several anthropoid characteristics. Like modern South American monkeys, Eosimias had small incisors and large canines. The back corner of its lower jaw was rounded along the bottom, as is the jaw of humans and other higher primates. Eosimias also had distinctive premolars and molars, Beard notes.

The Carnegie finds challenge current ideas about the evolution of higher primates. Elwyn L. Simons of Duke University in Durham, N.C., reported earlier this year that the oldest well-documented anthropoids come from 36-million-year-old rocks in Egypt, suggesting that such creatures arose in Africa not long before then (SN: 7/1/95, p.6).

But if higher primates were wandering around Chinese jungles 45 million years ago, anthropoids must have evolved much earlier, possibly in Asia, says Beard. The Eosimias fossils also suggest that early anthropoids developed from animals related to modern tarsiers and an extinct group called omomyids, he adds.

Other paleontologists hail the new Chinese fossils but question Beard's interpretation. "It certainly looks a lot more like a primate than what he had before. Whether it's an anthropoid ancestor or not, I'm not sure," says Gregg F. Gunnell of the University of Michigan in Ann Arbor. "What's missing is we still don't have a skull. Without a skull it's going to be hard to say."

Gunnell also disputes the idea that higher primates are closely related to omomyids. Instead, he finds evidence that anthropoids share closer bonds with lemurlike creatures called adapids.

Although Beard's ideas remain controversial, the new finds underscore the great potential of future finds in China and nearby countries, says Duke's Richard F. Kay. "There is a whole evolutionary history of primates that's virtually undocumented in Asia."