I don’t know, aside from the fact that the same species but in different areas, do have differing birth rates that can be correlated by the species chance of survival is genetic or otherwise.
What I’ve read about genes themselves is that they are responsible for our physiology, but they don’t seem to have much to do with our behaviours. However, there is a, if you will, a subset of genes called epistomological (I probably mispelled it :) ) that does seem to be affected by our behavious and that is where one might be able to trace why behavioural tendencies tend to run in families.
Exactly. A hypothesis exists. Without well-designed, repeated experimental tests, it remains a hypothesis, and its information value is null.