Selection pressures for long hair and beards in humans?

[Politesse]

I ask again: what makes you think our hair, or lack thereof; our beards, or lack thereof; are adaptations? Why can’t they just be accidents?

If I may interject, there are ways to determine whether a factor emerged due to selective advantage or not, and trends in facial hair do qualify in that 1.) they are often relatively homogenous in particular family populations, but 2.) also show strong regional trends that correspond roughly to climactic history. You have highly specific patterns of hair growth in particular villages or families, for instance, but not too far outside of macro-regional rules like hair volume being predictably correlated with latitude and altitude. I don't think it is wild to suppose that proclivities for certain kinds of hair growth have connoted a selective advantage at certain points in the past, because they behave like traits that do. Note that it's not just volume either, hair analysis in forensic settings yields a surprising amount of information albeit not all relevant to genetics.

Zooming out from populational comparisons, the fact that hair volume is also sexually dimorphic, in a species that has relatively few anatomically dimorphic traits by sex generally, shouts "sexual selection" as the most obvious hypothesis. But such hypotheses are almost never possible to confirm. They are the realm of rational or irrational speculation, and if one isn't careful, the dreaded just-so story.

 

[excreationist]

Some thoughts - the potential to have long hair and a long beard could exist so it is easy to distinguish between a homeless man and a well groomed man.... the well groomed man would be a better provider.... or something like that....

Do you really believe that there were well groomed men with cool haircuts and neatly trimmed beards running around 50,000 years ago? Or 200,000 years ago?

As I said in post #96 I consider cutting hair or beards to involve grooming - while on the other hand horses never cut their long hair.

BTW this says that people started wearing clothes 170,000 years ago:

Why did humans start wearing clothes? | Britannica Beyond

For centuries, early humans went about their lives in a natural state--aka naked. But according to recent studies, about 170,000 years ago our ancestors began wearing clothing. Why? It appears that two factors played a role--loss of body hair and migration. Early humans were covered in fur...

beyond.britannica.com

If they can wear clothes I don't think that's much more of a stretch that they'd cut their hair and beards eventually - otherwise they'd have beards that are a foot or more and if they have afros they might be a foot or two.