A small piece of jawbone unearthed in a cave in Spain is the oldest known fossil of a human ancestor in Europe and suggests that people lived on the continent much earlier than previously believed, scientists say.
The researchers said the fossil found last year at Atapuerca in northern Spain, along with stone tools and animal bones, is up to 1.3 million years old. That would be 500,000 years older than remains from a 1997 find that prompted the naming of a new species: Homo antecessor, or Pioneer Man, possibly a common ancestor to Neanderthals and modern humans.
The new find appears to be from the same species, researchers said.
A team co-led by Eudald Carbonell, director of the Catalan Institute of Human Paleo-Ecology and Social Evolution, reported their find in Thursday's issue of the scientific journal Nature.
The timing of the earliest occupation of Europe by humans that emerged from Africa has been controversial for many years.
Some archeologists believe the process was a stop-and-go one in which species of hominins — a group that includes the extinct relatives of modern humans — emerged and died out quickly only to be replaced by others, making for a very slow spread across the continent, Carbonell said in an interview.
Until now the oldest hominin fossils found in Europe were the Homo antecessor ones, also found at Atapuerca, but at a separate digging site, and a skull from Ceprano in Italy.
Carbonell's team has tentatively classified the new fossil as representing an earlier example of Homo antecessor. And, critically, the team says the new one also bears similarities to much-older fossils dug up since 1983 in the Caucasus at a place called Dmanisi, in the former Soviet republic of Georgia. These were dated as being up to 1.8 million years old.
"This leads us to a very important, very interesting conclusion," Carbonell said. It is this: that hominins which emerged from Africa and settled in the Caucasus eventually evolved into Homo antecessor, and that the latter populated Europe not 800,000 years ago, but at least 1.3 million years ago.
"This discovery of a 1.3 million-year-old fossil shows the process was accelerated and continuous; that the occupation of Europe happened very early and much faster than we had thought," Carbonell said.
Chris Stringer, a leading researcher in human origins at the Natural History Museum in London and not involved in the project, said Carbonell's team had done solid dating work to estimate the antiquity of the new Atapuerca fossil by employing three separate techniques — some researchers only use one or two — including a relatively new one that measures radioactive decay of sediments.
"This is a well-dated site, as much as any site that age can be," Stringer said.
But he also expressed some caution about Carbonell's conclusions.
First of all, the newly found jawbone fragment, which measures about two inches long and has teeth attached to it, preserves a section not seen in the equivalent pieces found at Atapuerca in 1997. So assigning both to the same species must be provisional, Stringer said.
And on the broader issue of tracing the new fossil back to the species unearthed at Dmanisi — Carbonell's big leap arguing continuity — Stringer said this too must be tentative because it is based on just a piece of a front of a jawbone and the time lapse is half a million years.
"That is a long period of time to talk about continuity," Stringer said.
Still, there are similarities between the two and this along with other archaeological evidence, suggests southern Europe did in fact begin to be colonized from western Asia not long after humans emerged from Africa — "something which many of us would have doubted even five years ago," Stringer said.
Carbonell says that with the finding of human fossils 1.3 million years old in Europe, researchers can now expect to find older ones, even up to 1.8 million years old, in other parts of the continent.
"This has to be the next discovery," he said. "This is the scientific hypothesis."