Never posted here before but this … interesting… essay I happened to stumble upon seemed to fit the bill too well to pass up.

original post: https://www.reddit.com/r/biology/comments/dwvfqz/why_does_prostatestimulation_in_men_produce/?st=k4evpc7d&sh=c20778cb

The key conclusion(s):

The most readily visible explanation for prostate-arousal just requires one to look at where the prostate is and how it is stimulated. It is stimulated by putting things into the rectum of the person. This is part of the digestive tract, the place where poop is naturally stored. Knowing that it is not a penis that is stimulating the prostate, yet the prostate still must be stimulated regularly in a way that increases the person’s ability to reproduce successfully, the only reasonable suspect here is poop. This would mean that poop is what naturally stimulates the prostate, and when poop stimulates the prostate, the person has a greater chance of reproducing successfully, meaning that the children go on to survive and themselves reproduce. This also means that those who lacked prostate stimulation were less capable of surviving; otherwise the phenomenon of arousal from prostate-stimulation would not have become present in all humans as those who did not experience this stimulation would not have died out or been forced into extinction.

Poop is the key here, because to have poop in your system you must be eating. You must be healthy, having solid, substantial stools that stay inside of your rectum rather than other types of feces produced, often by diseases like cholera or otherwise that would give you loose watery stool. Only this solid poop is capable of providing the stimulation. Solid poop is visibly very similar in look and shape to a penis or fingers, which explains why both are capable of stimulating the prostate in the same sense as poop, all while watery poop or a lack of poop due to hunger cannot.

The poop-dependent arousal induced by the prostate gives people an instinct that compels them to reproduce when times are good, meaning their children are likely to survive, rather than the instinct seen in other animals that take any opportunity they can find to reproduce.

This is a mix of coincidence and survival here. Poop is similar in shape and size to a penis, and as we can deduce that nothing in nature occurs due to pure randomness, this means that there is a reason that poop in humans is the same shape as a penis, and this holds true even in other animals known to engage in male-male anal sex such as wolves, whose poop is also a similar shape to their own penises.

The ability for the anus to receive the penis is a survival mechanism. This is an advantage because in a situation where a person is anally raped by a man, if their rectum is readily pierced by this and they just die from internal bleeding, this makes them unable to reproduce. If the rectum could not tolerate a penis, then this means that anal rape becomes a lethal weapon, beyond the disease it may spread, because the rectum is ruptured or otherwise severely damaged by this rape in a way that kills the victim. The anus evolves to tolerate this anal sex because it is an advantage to survive this situation rather than die due to being anally raped.

The author’s profile also includes some essays I haven’t yet had the pleasure of reading, but with titles like “Why am I a Proponent of Child Labor? Because it’s Good for the Children,” “I Wish Everyone Could Read Well Enough That They Didn’t Turn their Nose Up in Disgust at a Paragraph,” and “Why are the Jews so irrationally successful? Biology,” I’m sure they’re gems.