I think I can clarify that neither I, nor Disinfo Agent, are ignoring the importance of genetic factors in determining various individual traits, including aptitudes. The sole question of the OP is, once you average the genetic variances over a large population that has some chosen genetic differential, like the presence or absence of a Y chromosome, does the variance average out in that large population comparison, leaving only the common environmental agents as causal of the population differences?

That question cannot be answered by looking at brain physiology, nor even exam scores, by themselves. It can only be answered, on a trait-by-trait basis, by looking at data that is properly controlled for environmental agents. When one does that with gender and math aptitude, one finds no convincing evidence there is an innate difference-- and plenty of evidence that there is not, such as the OP and the study mentioned by parejkoj. All of that evidence is purely scientific-- none of it is based on "PC" preconceptions. This is what DA and I have been saying consistently throughout.