The following is an excerpt.
One of the pitfalls about talking about genetics, especially human genetics, is that the public wants a specific gene for a specific trait. Ergo, the “God gene” or the “language gene.” In some cases science has been able to pull a rabbit out of the hat, and offer up a gene for a trait. But in most of those instances these are going to be single gene recessive diseases. Not exactly what the doctor ordered. In other cases the association seems trivial. For example, wet or dry earwax?* What people are truly interested in are the genetic basis of complex traits, such as intelligence, personality, and height…
For most complex traits of any great interest it is not feasible for someone to list off the genes which control most of the normal variation on that trait. Pigmentation is an exception to this. While the continuous variation in height or intelligence seems to be distributed across many, many, genes, (on the order of hundreds or thousands) most of the variation in pigmentation seems to be collapsed into a few genes of large effect.
View the original article here: Pigmentation: the simplest of complex traits not so simple?