Nearly all babies are born sexed as male or female and can be identified as Boy or Girl on a Birth Certificate. Their birth sex is a very good predictor of subsequent bodily changes, liabilities and capacities through puberty to old age. This predictability is independent of culture. There are no cultures in which human females develop prostate cancer and no cultures in which human males get pregnant and give birth .
But is birth sex a good predictor - independent of cultures - of anything else? For thousands of years, every known culture has answered Yes! to this question and for a few decades political correctness has answered No!
I always felt that it would be very odd if males and females only differed in anatomy and blindingly obvious bodily facts linked to that. At the same time, I felt that it would be most unlikely that the differences would simply be the ones insisted on so strenuously by male-dominated cultures and usually to the advantage of males - though not always so: if males define themselves against females as natural fighters then, naturally, they are more likely to get killed. The military cemeteries of the First World War are very good testimony to where this belief about themselves landed them. It doesn't look like the work of male self-interest.
Leave that aside.
More likely, I felt, many or most natural differences between males and females would be things we did not think of first time round. They would be culture - independent tendencies which might show up in behaviour and might not, depending on how cultures responded to them. They might be relatively complex tendencies which cultures didn't fully grasp and so could neither repress or encourage consistently. In other words, they might or might not escape the whole business of cultural gendering which turns most males into Boys and Men and most females into Girls and Women.
In addition, and politically incorrectly, I felt that the whole business of cultural gendering would sometimes be working with the grain of natural tendencies and sometimes against it. It ought to be possible to distinguish those different cases and to look at what happens when Culture has an easy ride and to compare that with cases where it doesn't.
For example, it would be cruel of Nature not to incline females to at least some enjoyment of pregnancy, childbirth, breast feeding and early nurturing of their babies. If Nature was even just a little bit kind to females, then Cultures would have an easier task erecting onto this natural basis elaborate ideologies of Motherhood. You may end up with clap-trap but clap-trap which at least initially went with the grain of natural tendencies.
In contrast, consider how it would also be cruel of Nature to incline females against enjoyment of sex. It is sometimes said that Nature makes females less interested in sex because that protected them against unwanted pregnancy. On that basis, whole ideologies of female Modesty can be - and have been - constructed.
But this claim makes the mistake of equating sex with vaginal intercourse, which is itself a fairly bold ideological move. If you don't make that move, you can say (for example) that females have no disinclination to seek sexual pleasure and that when Cultures try to argue otherwise, they are opposing the grain of a Natural tendency. When that happens, you can end up not only with ideological clap-trap but public beheadings. Maybe that is the consequence of a Culture barricading itself against recognition and acceptance of a powerful Natural tendency.
The spirit of Political Correctness is probably right since it raises the bar to admitting claims to Natural differences between the sexes. But it becomes an oppressive ideology to be resisted when it insists, on principle, that there are no differences to be discovered. Maybe there are differences and we have so far not been very good at discovering them or their implications.