1.Brain scans showing differences in structure and/or function, used to identify transgenderism
2. Physical sexual dimorphism, which through a lifetime of social interaction can lead to different average behaviors (like growing up being stronger/weaker than 50% of the population)
3. Different concentrations of and responses to behavior altering hormones (testosterone/estrogen in particular)
4. Millions of years of evolutionary specialization through sexual dimorphism
5. Consistent differences in performance on various psychological aptitude tests (e.g. men and women have different average scores in spatial reasoning tests)
This is only a partial list, and I won't put the effort into citing any of this but it's all a Google search away, if you're willing to accept the unpopular but, IMO, glaringly obvious opinion and actually look for it. Of course there is also a well established bias in academia and the subject is sort of off limits, except in the case of transgender studies.
At the very least one shouldn't be so quick to immediately scream discrimination when there are so many alternative explanations rooted in genetics.
> In practice, the kind of differences in performance and achievement that would be explained by [discrimination] are immediately blamed on [psychological and physiological differences between men and women]. There is an implicit assumption that men and women are [inherently different], which leads to the conflation of equality of opportunity with [disparity of outcome], exaggerating the effects of [inherent differences] and leading to poor allocation of resources in an attempt to correct a "problem" without consideration for part of all of the actual cause.