Fossils Alter View of When Humans Arrived in Europe

A cache of startlingly human-like fossils from a Spanish cave is rewriting the early history of Europe. Researchers say the fossils represent a new species of proto-humans that push back the occupation of Europe by more than 300,000 years, changing anthropologists’ notions about exactly who migrated out of Africa into the rest of the world.

The 800,000-year-old fossils, which represent the last common ancestor of modern humans and the Neanderthals who flourished throughout early Europe, bear facial characteristics commonly seen only in much more recent fossils.

The finding, reported today in the British journal Nature by a team from the National Museum of Natural Sciences in Madrid, is only the latest in a series of discoveries suggesting that the human family tree looks more like an oak than a palm, sprouting large numbers of branches that withered in evolutionary dead ends.

“It’s clear that the Spanish team is on to something pretty important,” said paleoanthropologist Philip Rightmire of the State University of New York at Binghamton. “They’ve got a wealth of material, and it is all dated securely to 800,000 years ago. That’s the earliest human remains from anywhere in Europe.”

“We believe that this is a new species that we have called Homo antecessor,” from the Latin word meaning an explorer or one who goes first, said paleobiologist Jose Maria Bermudez de Castro of the Spanish museum, lead author of the report. “It’s a species that we consider the common ancestor of modern humanity and the Neanderthals.”

The new fossils “give us an idea of the amazing variation in [human ancestors],” said paleoanthropologist Jean-Jacques Hublin of the National Center for Scientific Research in Paris.

Although some researchers question whether the fossils are indeed a new species, their unquestioned antiquity is certain to provoke much discussion about the dissemination of hominids--the scientific term for two-legged mammals--from their first home in Africa.

Hominids are commonly believed to have started spreading outward from Africa as long as 1.8 million years ago. But no bones older than 500,000 years have previously been found anywhere in Europe.

Bermudez and his colleagues made their discovery at a site called Gran Dolino in the reddish Atapuerco hills of northern Spain. There, railroad workers blasting a tunnel in the late 19th century exposed cross-sections of bone-filled limestone caverns. Different layers date from as recently as 170,000 years ago to as far back as 800,000 years ago.

Excavating in the deepest, oldest layer, the team found more than 80 fossils, including skulls, jaws, teeth and other bones from six individuals. The centerpiece of the collection was a youth’s skull.

That face had such modern features as sunken cheekbones, a horizontal ridge where the teeth attach rather than the vertical ridge found in earlier species, and a projecting mid-face and nose.

Not everyone agrees that the material represents a distinct new species, however. Rightmire cautions that the only facial bones are from a boy, probably 11 or 12 years old. Skulls from the young often change as the individual ages, he noted. “It’s always tricky to compare children to adults,” he added.

Counterbalancing the modern characteristics, however, are a prominent brow ridge like that of the Neanderthals and the multiple roots for premolar teeth characteristic of early hominids. The Spanish team concluded that this unusual mix of traits was unique, justifying the need for a new species classification.

The team said H. antecessor was heavyset, of about average height and with a brain capacity of about 1,000 cubic centimeters, considerably smaller than modern humans.

The climate in Spain 800,000 years ago was much like that of today, according to Bermudez, and H. antecessor most likely lived in open forests of oak, pine and beech. Like their kin in Africa and Asia, they were hunter-gatherers and probably scavengers as well, although the stone tools found with the fossils are more primitive than contemporaneous tools from Africa.

One unusual aspect of the fossils is that the bones show tool marks, indicating that flesh had been scraped away just as with animals killed for meat. Such markings are normally associated with cannibalism, a rare occurrence among hominids but not a unique one.

Exactly where H. antecessor fits into the chain of human evolution is still the subject of some argument.

Up until about 10 years ago, that chain was thought to proceed, step by step, from Homo habilis, the toolmaker, through Homo erectus, who stood upright on the plains of Africa, to archaic Homo sapiens, the direct ancestor of both Neanderthals and us.

But new fossil discoveries and more sophisticated analyses of old ones have revealed a much greater complexity. It is now clear, Rightmire said, that many early hominids were evolutionary dead ends that died out abruptly--either because of climate changes or because they were unable to compete with hominids from other branches.

The Neanderthals are the classic example of this latter problem, unable to match the more quickly evolving Homo sapiens. “There are probably very few of their genes in modern humans,” Rightmire said.

The fullness of the human family tree means that the evolution of hominids was like that of virtually all other animals, full of mistakes and false starts that ultimately led nowhere.

Before the current discoveries, many researchers believed that the immediate predecessor of both humans and Neanderthals was Homo heidelbergensis. They thought that this species migrated to Europe 500,000 years ago, where it diverged into the two more recent species.

Comparing traits of skulls from a variety of species, the Spanish team concludes that it was actually H. antecessor that migrated to Europe, probably about 1 million years ago. There, the evolution continued, first to H. heidelbergensis and then reaching a dead end in H. sapiens neanderthalensis.

Some members of the species also remained in Africa, where they evolved into modern humans, the team argues, migrating to Europe at a later date.