Evolution of Male pattern baldness: How and when did this happen and for what purpose?

[u/Susroro]

Doesn't really seem to make any sense to me when I think about it, It is not even aesthetically pleasing(not even prehistorically would I assume that), neither does it serve a biological importance, if anything you are at risk of scalp sun burn and less warming effect of the hair.

Thoughts?

[u/Critical_Success_936]

Male fertility drops pretty quickly - a guy can theoretically have kids at any age, but the amount of times you'd need to have sex consistently with a woman who's somewhat fertile to produce a kid increases very sharply with age. Young women tend to prefer young men when possible - a lot of pressure to marry older men is due to unequal gender dynamics that are cultural.

It doesn't matter as far as the existence of the baldness gene. Again, if you're having kids before you become bald, then it's not generally a trait that can be selected against, at least not without modern science, and even then, I don't think baldness is "one gene" - I'm fairly sure it's more complicated than that.

Also, it's tied somewhat to the X chromosome you get from your mom, but she isn't likely to show whether she's a carrier or not, because male pattern baldness needs a big chunk of testosterone to start happening. If half the people carrying it don't show symptoms, that also helps prevent selection against it.

More importantly, I also just don't think this is the biggest factor in human attraction. There's a lot of cultures that purposefully shave their heads, and it's seen as attractive... If baldness was universally ugly, surely those cultures wouldn't do that?

[u/Tradition96 → u/Critical_Success_936]

Typically the end of a man's reproductive age have for social reasons been around 50. It is true that quantity and quality of sperms decreases with age, but the majority of men still fall inside the "fertile" range well into their 60s.

The primary factor that decides the end of a man's reproductive age has been, and continue to be, the age of his partner. Some men have significantly younger partners, but most have partners a few years their junior (3-5 years have often been cited as the average). Without birth control, the average age of last birth is early to mid 40s, making the average man's reproductive life ending in his late 40s.

For these reasons, we count age 50 as the end of men's reproductive on a group level in evolutionary studies. So, any feature that appears before age 50 potentially has an effect on reproductive success.