Denisovans: Homo erectus after all?

Greg Cochran:

The new paper in Science about an Australian genome (An Aboriginal Australian Genome Reveals Separate Human Dispersals into Asia) hints at something new. Comments in the supplement (and by Ann Gibbon) suggest that the Denisovans may stem from Homo erectus, at least in part, rather than being a sister group to Neanderthals as suggested in the paper by Reich and Patterson back in December. In the supplement, the authors suggest that they may be a sister clade to the last common ancestor of Neanderthals and modern humans. Ann Gibbons say the same, concerning the Denisovan girl whose pinky we found: “She was not a modern human, but a descendant of Homo erectus, an ancestral species that left Africa almost 2 million years ago. “

Denisovan mtDNA is deeply diverged from modern human or Neanderthal mtDNA, while the Denisovan teeth found look strangely old-fashioned. Moreover, it now looks as if admixture between hominid subspecies is the norm rather than the exception. So, although Denisovans as an admixture between H. erectus and some branch of Neanderthals was always a possibility, evidence, signs, and portents are starting to make it look likely.

From the supplementary data (pdf) for the Aborigine genome paper:

Denisovans are more elusive. The term refers to a hypothetical population or possible species of archaic hominin, identified on the basis of ancient DNA, and with possible genetic affinities to both H. erectus and H. sapiens/neanderthalensis. They have been proposed as a sister clade to the last common ancestor of Neanderthals and modern humans.