Silly perhaps, but fair. Humans break on tribal lines at the drop of a hat/naqib/dreadlock, and the genes for height in the above example could easily be replaced with the genes for melanin production, where each of presence and absence of the latter has funky social effects that vary from place to place.

Going back to the story, gender is, in humans, a complicated mess. Probably is in other species too (it's not just male dogs who try to hump your leg… although is that a sign of trans male dogs or just reusing an existing behaviour for multiple situations, the female canine behavioural equivalent of male nipples?)

Yes, some things happen for a clear reason, but sometimes the reason is "that's not a harmful mutation".