. . . and then takes some lumps

Although splitters now stand in the scientific spotlight, lumpers refuse to bow out quietly. In fact, their dismay at proliferating evolutionary categories, or taxa, for hominid fossils led them to convene a symposium titled “Read our lips, no new taxa.”

Computer models of species formation, which account for genetic influences often overlooked in fossil studies, don’t identify skeletal traits that

specify more than one Homo species, reported John D. Hawks of the University of Utah in Salt Lake City.

The genetic differences measured among the 14 proposed hominid species must add up to roughly the 1 percent genetic disparity between people and chimpanzees, said Robert B. Eckhardt of Pennsylvania State University in State College. On average, he added, these fossil species were about as genetically similar as modern ape species that interbreed in the wild.

Ancient hominids, such as Australopithecus and Kenyanthropus, may have spread to different habitats and evolved distinctive skeletal features, yet still interbred enough to remain a single species, Eckhardt proposed.

Eckhardt is skeptical of the splitters’ characterization of hominid evolution as a bush with many genetically distinct branches. “The bushier it gets, the more likely it is that genes will be exchanged,” which is good news to lumpers, he said.