That’s something I think many cisgender people don’t realise, or think about. We’re all born with the same template, and our hormones then decide what particular bits of the recipe our bodies should follow – so for example in the womb a rush of hormones tells us whether we should grow male or female gonads; in puberty hormones tell us whether to grow breasts or beards. But the template for both sexes remains, so if you take somebody born male, suppress their testosterone and increase their estrogen then their body (and their emotions; jeez, the emotions…) will change.
Reproductive systems aside, men and women aren’t that different: the idea that there are huge biological differences between the sexes is largely based on status preservation.
Hormones aren’t biological now?