Monday, September 26, 2011

The Search For The Denisovians

New data on traces of Denisovian DNA in Asia makes the effort to try to link that pattern to the hominin fossils in the region more interesting.

The Denisovia cave DNA is dated to ca. 40,000 years ago and admixture with hominins of with similar DNA is thought to have occurred ca. 75,000-45,000 years ago in Southeast Asia. The earliest hominins in Asia, Homo Erectus, date to not quite 2,000,000 years ago. There is some evidence for intermediate types in Indonesia and China, and Homo Florensis from ca. 100,000 to 18,000 years ago in the same general region of Indonesia where Denisovian ancestry is found argues that Homo Florensis may have been a relict dwarf population of Denisovians as they are an archaic hominin group in the right place at the right time.

Estimates from genetics are that Neanderthals and Denisovians have a common ancestor ca. 1,000,000 years ago, around the time that intermediate species between Neanderthals and Homo Erectus emerge, such as Homo antecessor, Homo heidelbergensis, and Homo rhodesiensis - the extent to which these archaic hominins are different species from each other or from Homo Erectus is disputable. If these intermediate hominins in (mostly) Europe are the predecessor species for Neanderthals, and there was a single Homo Erectus species before that point, the emergence of these intermediate species could be the moment of the Denisovian-Neanderthal split.

The closest in time, arguably intermediate hominin fossil in Asia other than Homo Florensis is the Dali fossil of China. Ngandong 7 in Indonesia, the Hexian fossil from China, Sangiran 17 in Indonesia, Peking Man, and Java Man are all at dates consistent with potentially being Denisovians (1,000,000 to 40,000 years ago), or at least ancestors of Denisovians. These later specimens in Indonesia and China, particularly those with characteristics somewhat diverged from the earlier Homo Erectus fossils, are the logical matches to the Denisovians.

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