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?