I do not know.

It is a good question to me.

I do not even think I have a good idea why.

It seems to be uniquely human. Maybe some other great apes? I’m not really sure about that ape part though.

Why say groin hair? Maybe this is one possible idea. Let’s borrow earlier discussion.

There is confusion surrounding the persistence of the appendix in so much as appendicitis causes death in young reproductive people and should be actively selected against at a superficial level.

Something else that causes a similar number of deaths worldwide at least recently, not off from appendicitis, by more than a factor of 0.5, would be kidney stones

I suspect we don’t know nearly as much about the urinary Microbiome as we do the gut micro biome. At least some people think certain bacteria- Lactobacillus crispatus- may have a role in the urinary micro biome in preventing kidney stones, and in the vaginal micro biome in reproductive health.

Is it possible that groin hair helps create an environment that fosters Lactobacillus crispatus ? Helps create some sort of niche? Facilitates spread? Selects against competitor bacteria? This is almost certainly not right but at least it made me think…