MADRID, Spain - Scientists on Thursday announced the discovery of a common ancestor of both Neanderthals and modern man - a tall, lanky being who looked much like us except for his protruding brow and heavy jaw.
The discovery of Homo antecessor, - who hunted rhinoceroses, elephants and other game some 800,000 years ago in the forests of what is now Spain - could prompt experts to redraw the human family tree, a Spanish anthropological team said.
The new findings, which will be published Friday in the American journal Science, support the theory that the human family tree has many branches - instead of running along a single line - and that present-day humans share ancestors with human-like beings who eventually became extinct.
The Spanish scientists dug up 50 fossilized specimens from at least six individuals during excavations in the summers of 1995 and 1996, in the Atapuerca hills of northern Spain.
The scientists eventually realized they had found missing pieces of the human evolutionary puzzle, said Jose Luis Arsuaga of Madrid's Complutense University, one of the six scientists on the anthropological team.
"Our decision to name a new species came after trying to fit the fossils into all previous species from Europe and Africa," Mr. Arsuaga said. The team presented the fossils to reporters Thursday at Madrid's Museum of Natural Sciences.
The team named the species Homo antecessor, which means "man's forebear."
The largest fossils, from the skull of an adolescent male, are the centerpiece of the team's study.
Homo antecessor had a bulky lower jaw, primitive teeth, and a ridged brow - all typical of Neanderthals - and humanlike cheekbones and depressions on either side of the nose also typical of modern man.
"This combination of characteristics is unique. It doesn't appear in any other hominid," said Antonio Rosas, a co-author of the study published in Science. "From a logical viewpoint, it fits into an easily definable space - the common ancestor of Homo sapiens and Neanderthals."
Scientists disagree on whether Neanderthals, a primitive human-like being, were the ancestor of modern humans or a related but different species that died out 35,000 years ago.
While describing the team's findings as impressive, Rick Potts, curator of the Institute of Human Origins at the Smithsonian Institution in Washington, said the conclusions are also vulnerable to criticism for being largely dependent on a single, immature specimen.
"We all know that people vary in every population. The question that's going to be there in the minds of many anthropologists is, `What is the range of variation?'°" Mr. Potts said.