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Matt Ridley is the author of provocative books on evolution, genetics and society. His books have sold over a million copies, been translated into thirty languages, and have won several awards.

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New cousins

A new species of Pleistocene Central Asian hominin that left some DNA behind in Melanesians

The big news of the day, indeed of the year, is that we now know, almost for sure, that central Asian hominins 50,000 years ago were not Neanderthals, but a different species, the Denisovans, as distantly related to Neanderthals as they were to us. A genome extracted from a little finger found in the Denisova cave (above) in the Altai mountains of south-western Siberia seems to say so as does a morphologically distinct tooth.

But that is not the biggets surprise. Astonishingly, Melanesian people from Papua New Guinea have a 5% ancestral contribution from these Denisovans to their genomes. The implication: as Africans spread around the Indian ocean 50,000 years ago, they did some cross-breeding with Asian native hominins, who were of this hitherto unknown species that lived in Siberia (and presumably further south as well).

Holy Mackerel, what an incredible historical tool DNA sequencing is! Truly there is scripture in it.

I don't have time to explore this remarkable story and its implications today, because of holidays and snow, but I recommend John Hawks's analysis, of which this is an extract:

Well, it's obviously very exciting, but I find it very difficult to talk about these Pleistocene populations without falling into bad habits.

Our common ancestry as humans goes back to the Early and Middle Pleistocene. The (now multiple) Neandertal genomes and the Denisova genome share genes with some people and not others because of this common ancestry.

In addition, some living people carry even more genes from Neandertals because they have an appreciable fraction of Neandertal ancestry. That makes it nonsensical to talk about "Neandertals and the ancestors of modern humans". Neandertals are among the ancestors of modern humans.

Just so with Denisova. It's nonsensical to talk about a three-way split between Neandertals, Denisova and modern humans. We can talk about a population model with a clade separating an ancestral Neandertal-Denisova population from contemporary Africans.

I have to remind myself again and again when I talk to people about these issues that "modern human ancestors" is not a group that excludes these Pleistocene people.

Were they capable of exchange?