Science / Medicine : Fossil Find Puts Start of Human Line Much Earlier

Fossils found in Wyoming indicate that the line of monkey-like animals that apparently led to human evolution may have diverged from other primates 15 million years earlier than previously thought, researchers from Pittsburgh’s Carnegie Museum of Natural History and the Denver Museum of Natural History reported last week in Nature.

The researchers found four fossil skulls of a mouse-sized mammal they named Shoshonius in Wyoming’s Wind River Basin. Like living tarsiers (a lemur-like primate from the Philippines and East Indies), Shoshonius had enormous eyes, a very short muzzle and enlarged bony ear chambers. These and other features of its skull anatomy indicate that Shoshonius and modern tarsiers evolved from a common ancestor 50 million years ago, and that the anthropoid lineage already had split off by that time.

The oldest known previous fossil anthropoids are from Africa and are 35 million years old. “This means that the fossil record of at least the first 15 million years of anthropoid evolution is missing and awaits discovery,” the authors said.

In an editorial accompanying the study, Robert Martin of Switzerland’s University of Zurich said the Wyoming discovery “dramatically augments our knowledge” of early primates and “tends to confirm the suggestion that divergence times in the primate evolutionary tree may be markedly earlier than has been generally accepted.”