I mean some fetishes have science behind why they exist. For example, the part of the brain that process feet is located next to the area that processes genitals. At least, some are explainable. Some are not.
Well, if natural selection had a say, the only fetish anyone would have would be an impregnation fetish. (Only half joking.)
Natural selection had a say in female mammals leaking blood trails every month, which is, mildly said, fcking stupid. Natural selection does not create optimal beings, it creates stuff that, somehow, kinda, works.
If you have the time for it, I highly recommend the lecture series on behavioral evolution by Robert Sapolsky, it's on the Stanford YouTube channel.
It's stupid from a practical perspective but the energy required to build up the uterine lining and tear it down on a (basically-)monthly basis is much lower than its upkeep