"They used the stone tools to take meat off animals, cut the muscles, and break their bones," Bermúdez de Castro said. "The bones show the marks of these implements."
Remains of other close-by animals—including rhinoceroses, deer, bison, lynx, wolves, and bears—were also used to help date the fossils, the study said.
An abundance of small, insect-eating species suggests the climate then was generally warm and humid, the study added.
The research opens an interesting new chapter in the story of European colonization, the study authors say.
The earliest known human fossils found outside of Africa are from Dmanisi in the modern-day Republic of Georgia. Identified as either Homo erectus or Homo ergaster, the remains date to around 1.8 million years ago.
"The Republic of Georgia is at the gates of Europe," Bermúdez de Castro said. "It's the crossroads between Africa and Eurasia from a geographical point of view."
But H. erectus fossils estimated to be 1.6 million years old have been located as far away as Java in Indonesia, he noted.
Because of that, "we think that in Europe we are going to find more hominin fossils probably older than those of Sima del Elefante," Bermúdez de Castro said.
The Spanish-led team adds that the new fossil human likely marks the beginnings of a native European species represented by the younger finds at Atapuerca.
"We see that these fossils are different from other populations in Asia or in Africa," Bermúdez de Castro said.
"We think that when populations come to an extreme part of a continent, or to an island, a process of speciation usually occurs," he added. "This is very normal in the animal world."
The Atapuerca researchers in 1997 had suggested Homo antecessor as a possible ancestor of modern humans. But the age of the new fossil find makes this theory less likely, Bermúdez de Castro admitted.
"Homo antecessor may be very, very old in Europe, and modern humans came from Africa," he said, making the previous theory "difficult to support."
More likely, Homo antecessor gave rise to Neandertals (often spelled Neanderthals) in Europe, he said, adding, "it's a good hypothesis to test in the future."
"Important and Exciting Find"
Fred Spoor, professor of evolutionary anatomy at University College London, said the new fossil, assuming its dating is accurate, marks "undoubtedly a very important and exciting find."
While stone tools had suggested a human presence in Spain around a million years ago, convincing fossil evidence had previously been lacking, Spoor commented.
He also described the jaw as "remarkably modern looking" compared with similar or younger hominin fossils known from Africa.
"If we would find this kind of mandible in Africa, we would be a bit surprised," Spoor said.
He added that the idea that the Atapuerca hominins represent a distinct European species is entirely plausible, given that the region would have been a far-flung human outpost.
"Spain is about the furthest point you could go to the west," Spoor said. "It's a bit of a cul-de-sac, so in that sense you would get speciation where something wanders off on its own."
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