Monday, August 3, 2015

Diversity II: The Power of Genetics

CBS Morning News reported on a new study published in Nature looking at 350,000 people worldwide that showed genetic diversity of parents had no health effects on their children.  In the process, however, they did find another surprising result.  “Greater genetic diversity is linked to an increase in height and enhanced cognitive function, a new study finds.”

I found a couple of aspects of this study interesting.  The first question I had was whether this was another one of those studies where so many variables were tested that it was likely that at least one or two of them would show statistical significance – a kind of throw-it-at-the-wall-and-see-what-sticks approach to science.  Does it count when they are looking at one thing, health effects for example, and another one pops up in an oh-look-what-I-found way?  It was a very large sample size, but it seemed a little odd that they expressed it in number of people, when they were actually sampling couples.  Finally, I was a little surprised that they could find and test DNA samples from both parents for such a large number of people.

To figure some of this out I went to the study.  There was no genetic testing.  The differences were inferred from the fact that parents came from geographically distinct areas or from socially isolated population, e.g. Amish.  Since the world has become better connected, it is now more likely that individuals from genetically different populations would meet and mate, which may help explain in part why in the general population height and measured intelligence have been increasing.  (It has somewhat the opposite effect of inbreeding – except that analysts found no particular health implications.)

The journalists who reported this seemed from their questions and reactions to take for granted that genetically diverse is the same as racially diverse, the popular definition of diversity.  This brings up another question:  Really how genetically different are what are commonly referred to as different races?  There is some science here. 

An interesting article from last year explains:  Human races are not natural genetic groups; they are socially constructed categories.  Furthermore, the level of genetic differentiation between human populations falls well below the threshold that biologists typically use to define races in non-human species.” 

Other recent research shows that race can be distinguished by DNA analysis.  But this 2014 Time article is careful to point out that the differences are minuscule.  “The overwhelming verdict of the genome is to declare the basic unity of humankind.”

We should find this to be refreshing.  Instead of emphasizing differences we would be well justified to concentrate on our similarities.  If we are genetically 96% similar to a chimpanzee, how different from each other can we really be – regardless of physical characteristics?

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