White skin -
Neanderthal inheritance
My younger son Daniel
pointed out to me an error in my last post, the topic of which was a recent
increase of the frequency of rickets in children in the UK. As would be
predictable from previous experience, the incidence was higher in children of
South Asian and Black ethnicity than in white children.
I mentioned in the Post that the dark skin people living in tropical parts of the world is an evolutionary adaptation to the
high intensity of the sun. Daniel
pointed out that strictly speaking this is not correct, as Homo sapiens
originated in Africa and the vast majority of the world population is
dark-skinned, living in tropical or semi-tropical zones.
It is the white-skinned
population of the world that is a small minority, differing from the majority,
and it is this group that is an evolutionary variant, and adapted to living
only in the northern temperate area of north-west Europe. What was the origin
of this small group?
Neanderthal (Neander
tal) is a valley close to Dusseldorf in Germany. It is indicated by a sign on
the autobahn viaduct that crosses the valley. Skeletal remains of a humanoid species were first discovered in the valley in the 18th
century and have since been discovered in other parts of Europe. The humanoid became know as Neanderthal Man, scientifically Homo sapiens neanderthalensis.
Recent genetic studies
have shown that the white-skinned variant of Homo sapiens has in the genome some DNA derived
from the now extinct species Neanderthal Man. In other words at some time in the distant
past there was a small amount of interbreeding between the new Homo sapiens spreading
out of Africa and the older Neanderthals living in Europe, about 60,000 years
ago. Little genetic advantage was passed on to Homo sapiens but one is a genetic factor for fair skin, an advantage when living in northern Europe. Another genetic factor is fair straight hair.
Darwin introduced the
idea of “survival of the
fittest”, indicating that
if a new gene gives an advantage, then those with that gene will thrive. In
north-west Europe a pale skin gave an advantage in the form of enhanced vitamin
D synthesis.
And so, thanks to the Neanderthal humanoid, white-skinned
people are genetically adapted to living very distant from the equator. Dark
skin is the global norm of “pure” Homo sapiens. The Neanderthals became
extinct as Homo sapiens proved to be superior, but their genetic
influence lives on in white-skinned people.
http://www.newscientist.com/article/mg22129542.600-neanderthalhuman-sex-bred-light-skins-and-infertility.html#.U0WpP16AQpE
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