"I’m not sure why it’s so hard for people to believe that evolution can indeed affect our brains just like everything else."
because publicly acknowledging this obvious reality comes at a cost: you WILL be attacked. most people do not want to be attacked and would rather take the easier route of pretending to not notice this or anything that's going to cause them a problem.
they have even done studies with 1 day old babies where the scientist holds the baby's nose shut and guess what, babies of different races react in different ways. same as when they take baby boys and girls and put them in a room the boys go for the toy trucks and the girls go for the dolls. i'm sorry but that study doesn't need to happen if you don't live in an ivory tower and have to act like a politician because you have so much money to lose for having the wrong opinion.