European Roots: Human ancestors go back in time in Spanish cave

Fossil finds in Spain have yielded the earliest known skeletal evidence of human ancestors in Europe, according to a new report. A fossil jaw and tooth from the same individual, found during excavations of a cave called Sima del Elefante in northern Spain’s Atapuerca Mountains, date to between 1.2 million and 1.1 million years old, say anthropologist Eudald Carbonell of Universitat Rovira i Virgili in Tarragona, Spain, and his colleagues.

The investigators assign the new discoveries to the species Homo antecessor. A decade ago, they identified 800,000-year-old fossils from another Atapuerca site as H. antecessor. In the Spanish scientists’ view, H. antecessor was an evolutionary precursor of European Neandertals and modern humans.

Many scientists remain skeptical of that proposal and classify the Spanish fossils as the oldest examples of Homo heidelbergensis, a roughly 600,000-year-old species first found in Germany a century ago.

However this debate plays out, the Sima del Elefante fossils “provide the oldest direct evidence, to our knowledge, for a human presence in Europe,” Carbonell says.

Anthropologist Bernard Wood of George Washington University in Washington, D.C., agrees that the find provides the first solid evidence that human ancestors reached Europe more than 1 million years ago. “Before this report, the evidence for an early occupation of Europe had substantial and important caveats,” he says.

The newly unearthed specimens were found in sediment that also contained stone tools, stone flakes produced during toolmaking, and numerous animal bones bearing butchery marks.

Carbonell’s team describes its work at Sima del Elefante in the March 27 Nature.

Several lines of evidence provided an age estimate for the Spanish fossils. Reversals in Earth’s magnetic field recorded in fossil-bearing sediments bracketed the fossils’ age at between 1.78 million and 780,000 years old. The decay rate of certain radioactive isotopes in rock buried near the fossils—along with analyses of the types of now-extinct animals strewn among the finds—narrowed the age estimate down to 1.2 million to 1.1 million years old.

The new finds strengthen earlier, contested evidence from other European sites—mainly consisting of stone implements, not fossils—that suggests human ancestors occupied the region at least 1 million years ago, Carbonell says. A broad anthropological consensus holds that large groups of human ancestors lived in Western Europe by 500,000 years ago.

The Atapuerca investigators suggest that Western Europe was settled between 2 million and 1 million years ago by a Homo species that trekked out of Africa, perhaps into central Asia, and then moved westward. That species then evolved into H. antecessor, in their view.

One possible ancestor of the ancient Atapuerca population has been found at the Dmanisi site in the central Asian nation of Georgia. Excavations there have yielded 1.77-million-year-old remains that may come from an early, highly mobile form of Homo erectus (SN: 9/22/07, p. 179).

The Sima del Elefante fossils show no obvious anatomical links to the Dmanisi remains, Wood says. Still, an evolutionary connection between Dmanisi and Atapuerca is plausible, he says.

It’s unknown whether enough human ancestors entered Western Europe before 1 million years ago to establish a permanent presence in the region so that they could evolve into later European Homo species, Wood notes.