BRANCHING OUT

By MICHAEL D. LEMONICK

Finding a new species of bird or bug is a little like finding a new use for duct tape--nice but not earthshaking. Finding a new species of human ancestor, on the other hand, is always a big deal. That's why Spanish scientists spent three years studying fossils they discovered at Sierra de Atapuerca in northern Spain. They wanted to be sure of what they had.

Now they're sure. In the current issue of Science, Jose Maria Bermudez de Castro, of Madrid's Center for Scientific Investigation, and his colleagues maintain that their fossils belong to a new, possibly cannibalistic species of early man that roamed Europe nearly 800,000 years ago. Called Homo antecessor (from a Latin word meaning "explorer"), this creature may be the last common ancestor shared by modern humans and Neanderthals.

Age alone qualifies these fossils as a major find. Until they were discovered in 1994, human remains in Europe dated back only half a million years, in contrast to 1.8 million years in Asia and more than 2 million in Africa. And if the specimens represent a new species, the significance is even greater. Conventional wisdom had it that both humans and Neanderthals evolved from a species called Homo heidelbergensis that lived around 500,000 years ago.

The Spanish fossils, though nearly twice as old, show a mix of modern and Neanderthal facial traits. According to the new genealogy, H. antecessor evolved in Africa and gave rise to H. heidelbergensis and another, still undiscovered species. The former begat Neanderthals; the latter led to modern H. sapiens. Not all paleoanthropologists are convinced. But if this theory holds up, the human family tree has just grown another branch.

--By Michael D. Lemonick. Reported by Jane Walker/Madrid

With reporting by Jane Walker/Madrid