Anal sex, as you have called attention, is just so disgustingly repulsive (and, not to mentioned, highly dangerous from a hygiene point of view). E-coli bacteria from our intestinal tract just doesn't go with genitals. People are nuts who do this. Feces and love are definitely not made for one another.
It's generally the folks that take "Progress" as a given that forget just that.
Keuhnnelt-Leddihn put it well ... sure, things evolve but successful evolution involves accretion and synthesis. I think human beings (although not their essential nature) evolve quite a bit and it is their genuine, self-determined Progress that most distinguishes us from mere animals ... (if not also the Angels ... sigh ... we do have a bad habit of spinning out and cashing it all in from time to time)