Humans
do show some phenotypic and genotypic variation by geographical
origin. Geographic isolation after human migrations, and natural or
sexual selection, have resulted in some alleles being more
frequent in some groups that in others, and ancestry determines the
distribution of these gene variants, but this is only for a few genes.
That is basically the whole concept of "race" from a biological point
of view. It is a fuzzy one, because there is no precise demarcation
between ethnic groups, as humans have been migrating and moving around
the globe for a long time, in different migratory waves. In today's
world, with globalization and relatively easy world travel, geographic
isolation is a diminishing parameter. We meet and fall in love with
people whose recent ancestors came from all the continents in the world.
It makes even less sense nowadays to think of human ethnic groups as
"pure races" or "breeds".
If we feed genomic
data from thousands of people from all over the world, and we use
algorithms to find relatedness or to build trees or to find patterns of
genetic variation, we will get clusters that show that genetics mimic
geography to a large extent. But this is a pretty trivial fact,
and it makes perfect sense that people who have lived together within
one geographical region for thousands of years or even shorter times
will share more gene variants in common. If you use genomic data from
just Europeans, gene frequencies closely mirror geography .
And like the great Italian human population geneticist Luigi
Cavalli-Sforza reminds us, if we feed one of these programs genomic
data from people in neighboring tiny Tuscan towns, they will pick up
genetic differences between the inhabitants of neighboring towns
Sienna and Florence. Geography is a better determinant of genetics than
"ethnicity" (of course, depending on how we describe ethnicity; for
those not in the US, remember that "Hispanic" is an ethnicity) (Geography is a better determinant of human genetic differentiation than ethnicity).
A recent example was just published, finding genetic differences in
people original from the British Isles: these people all look the same,
the Welsh, the Cornish, etc., but you can differentiate them genetically
if you compare them to each other, because of the intrinsic genetic
variation and its association to geography (Fine-scale Genetic Map of Britain Gives Clues to Ancient Population Movements).
In
the scientific community, nobody doubts that ancestry is not of medical
importance, for example when it comes to genetic risk for certain
diseases, predictors of treatment success, or even as confounding factor
for genome wide association studies (GWAS, Genome-wide association study) aiming at finding gene variants associated with traits.
However,
does all of this say that race is not a social construct? It depends
how you define "social construct" and in which context. If you ask me, it's hard to minimize the importance of race as a social construct when Barack Obama will be forever know as the first US black president when genetically speaking he is as much white as he is black.
The fact that everyone perceives Mr. Obama as black speaks volumes as
to the importance of allelic frequencies in this debate: absolutely
zero. He is black, because to a country who was founded by Northern
European immigrants who pushed back the native American populations, and
brought people from Africa as slaves, where their descendants are still
subject to discrimination on the basis of skin color, hair type, or
general "looks", the social concept of race trumps any scientific basis
for it.
Ken Malik (ABOUT)
who has a scientific (neurobiology) background as well as one in the
philosophy of science, wrote a very good article a few years ago on the
subject of race as biological reality, or social construct, which I
highly recommend as it is very well written and very informative: WHY BOTH SIDES ARE WRONG IN THE RACE DEBATE
Regarding
the majority of the variation being present within groups, Ken Malik
explains it masterfully by summarizing two key studies:
Imagine that some nuclear nightmare wiped out the entire human race apart from one small population – say, the Masai tribe in East Africa. Almost all the genetic variation that exists in the world today would still be present in that one small group. That is a dramatic way of expressing the results of a landmark analysis conducted by the geneticist Richard Lewontin in 1972. Lewontin showed that virtually the entire range of human differences – 85 per cent – occurred between individuals within single populations. A further 7 per cent differentiated between populations within a race. Only 8 per cent of total variation distinguished what we call the major races.
Since 1972 other researchers have confirmed that 85 per cent of variation exists within a population. The results of a 2002 study by Noah Rosenberg and his colleagues were even more striking. They showed that differences among individuals account for a staggering 93-95 percent of all genetic variation. About 2 per cent is taken up by differences between populations within a race. And race accounts for just 3-5 per cent of all human difference. The study also found that almost half of the alleles appeared in every major population in the world. Only 7.4 per cent of alleles were exclusive to one region, and such alleles tended to be very rare. Rosenberg’s study is the largest of its kind and hence the figures are likely to be the most accurate.
Wishful thinking cannot inform policy, but neither should "sciencebabble".
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