Genetic exploration of the positive tail of normally distributed traits is important conceptually because it moves away from the notion that we are all the same genetically except for rogue mutations that cause disorders, diseases and disabilities.
Well, there's a straw man slain. Who seriously makes this claim?
I think a lot of this comes from the low percentage of genes that are not shared by all humans, approximately 0.1%. Of course, that .1 percent difference plays a huge role in the differences between people. We are barely more than 1% different from chimpanzees. Also, from the well established studies of how the environment has an influence on how genes are expressed. Two adult identical twins will express some of their genes in different ways due to their life long environmental path. If one considers all influences on a body with the exception of the initial genes one had at the moment of conception as environmental influences, the effect of the environment on all heritable characteristics can easily be show to be significant. This includes intelligence.
It has been extensively studied with identical twins in adopted homes. The converse has also be extensively studied, unrelated adoptive children in the same home. Given a large enough study one can with a high level of certainty show a correlation between genes and intelligence as well as a correlation between environment and intelligence. Both have a fairly well established correlation. It is not either or. Of course, as most people know correlation does not prove causation. The way I tend to view the problem is how a set of genes behave within some given environment.
for the numbers I will site:
http://humanorigins.si.edu/evidence/geneticsjust one study of environmental effects on gene expression.
http://www.nature.com/scitable/topicpage/environmental-influences-on-gene-expression-536Everything else is recalled from many sources or my own opinion.
