Many anthropologists suspect that hominids, ancient members of the human evolutionary family, branched into as many as 20 different now-extinct species over roughly the past 6 million years. At scientific meetings in Phoenix last week, two skeptical researchers took different approaches to pruning this species-laden scenario.
Their handiwork expands debate over how to identify hominid species in the fossil record. Still, proponents of what might be dubbed humanity's family bush remain steadfast.
In a controversial presentation, Tim D. White of the University of California, Berkeley accused many of his colleagues of ignoring geological forces that have substantially distorted the shapes of key hominid fossils and given them a false appearance of anatomical uniqueness.