This is a thorny discussion, but it appears that IQ is unevenly distributed and the differences in variance are even stronger. And the end result seems to be that if you select for IQ > 150 people, then you expect to see 80% men 20% women purely due to biological causes. Whether or not we (the society) should accept that outcome is a completely different thing. But if you average over enough people, there are very real development differences between genders and some of them are related to brain energy supply and/or brain volume. And I believe the GP was right, stress response is also heavily biologically modulated. It kind of makes sense that the average 1.6m women would respond differently to a hungry tiger than a 1.9m bodybuilder... right?