Spanish researchers have discovered 800,000-year-old fossils which they believe are a new species of early humans directly ancestral to us. If true, the find could force paleontologists to rewrite the human family tree, according to the team's report in tomorrow's issue of Science.* But while other paleontologists praise the new discovery, many are skeptical that the remains warrant listing as a separate species.
The fossils, the oldest known Europeans, were discovered in caves in the red limestone Atapuerca hills of northern Spain by paleoanthropologists José Bermúdez de Castro and Antonio Rosas of the National Museum of Natural Sciences in Madrid, Spain, and their colleagues. They are the remains of a boy and five other early humans. The Spanish team has named this putative new species Homo antecessor, from the Latin word meaning explorer or one who goes first. They say that the species's unusual mix of traits--in particular, the boy's modern face set between a primitive jaw and brow--show that it gave rise to both modern humans and Neandertals, the heavyset species that lived in Ice Age Europe until about 28,000 years ago.
The authors suggest that H. antecessor originated in Africa, where it gave rise to H. sapiens long before that species migrated to Europe. Perhaps about 1 million years ago, they say, H. antecessor itself migrated to Europe, and there it also gave rise to H. heidelbergensis, which in turn led to Neandertals. If H. antecessor is indeed the last common ancestor of Neandertals and modern humans, it could bump two other favored contenders--H. erectus and H. heidelbergensis--off the main line of descent leading to modern humans, making them side limbs on an increasingly bushy human family tree.
Other paleoanthropologists are impressed by the finds--more than 80 fossils, including skulls, jaws, teeth, and other parts of the skeleton--which offer new insight into a mysterious time and place in human evolution. "We now have a better window on the first peopling of the European continent," says paleoanthropologist Philip Rightmire of the State University of New York. Binghamton.
But identifying these people as a new species, not to mention claiming them as a key human ancestor, is highly controversial. "I think many of my colleagues will be uncomfortable with creating a new species, because it is mainly based on the facial features of one juvenile," says paleoanthropologist Jean-Jacques Hublin of the National Center for Scientific Research in Paris.