DNA from a 400,000-year-old leg bone from Spain - the oldest hominin sequence yet published - has revealed an unexpected link between Europe's inhabitants of the time, and the Denisovans who lived much more recently in southwestern Siberia. Most researchers believed the bones would be more closely linked to Neanderthals.
     The fossil was excavated in the 1990s from a deep cave in a well-studied site in northern Spain called Sima de los Huesos ('pit of bones'). The remains of more than two dozen other hominins found at the site have previously been attributed either to early forms of Neanderthals, who lived in Europe until about 30,000 years ago, or to Homo heidelbergensis, a loosely defined population that gave rise to Neanderthals in Europe and possibly humans in Africa.
     The team led by Svante Paabo, a molecular geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, sequenced most of the bone's mitochondrial genome. The result placed the DNA closer to that of Denisovans than to Neanderthals or modern humans. "This really raises more questions than it answers," Paabo says. Denisovans lived thousands of kilometres away and hundreds of thousands of years later.
     Paabo notes that previously published full nuclear genomes of Neanderthals and Denisovans suggest the two had a common ancestor that lived up to 700,000 years ago. He says the Sima de los Huesos hominins could represent a founder population that once lived all over Eurasia and gave rise to the two groups.
     The situation will become clearer if Paabo's team can extract nuclear DNA from the bones from the Sima de los Huesos hominins, which his team hopes to achieve within a year or so.

Edited from Nature (4 December 2013)