As I understand it, our genes are born ready for adaptation. IOW, our genes are not fixed. If our genes were fixed, people could not have survived in all the different environments on this planet. For example, here In America, people from all over the planet, survive in social environments as extreme as Alaska and the Mojave Desert to New York City, and Bucksnort, Tennessee.

Our genes adapt to whatever social environment we are born into. The same exact genes that produce a scientist in one social environment, will produce a serial killer in another social environment. Hence, it is our social environment that tells our genes which direction to develop in order to survive - not our eye, hair, skin or teeth colours.

However, the social environment of the region where we are raised determines our genetic adaptation far more than our family environment. Apparently, that is because the people in a region adapted to a social environment made necessary by that particular location (which, in turn, dictates the family environment). Hence, regardless of family make-up, the differences in people are more firmly rooted in the regions where they grew up, and came of age.

I think this is the reason, that the children of parents with unusually high talents, intellects, wealth, etc. are usually failures. Simply put, these heirs/children's genes are not adapting to the same environments that their parents did.