A Hairless Ape Question

[Atellus]

As I get older, I'm becoming hairier. This is not a complaint, you understand. I don't look forward to the possibility that conspicuous parts of it may one day fall out. However, at the same time, it occurs to me that this aspect of maturation does not deserve to be taken for granted. Why not? Well, for one thing, it doesn't seem to make sense.

 

I'm more hairy now than I was 10, or even 5, years ago. I refer specifically to body hair. Torso hair is what doesn't make sense. Obviously, it's all a left over from our primitive past but what we do have still contributes something on those chilly nights, and for our arguably slightly hairier immediate ancestors, every little advantage is worth the effort.

 

Scenario: a group of hunter gather homo sapien's a few thousand years ago. Climate is moderate, varying between warm but tolerable summers and cold but bearable winters. Individuals become sexually active quite early by modern standards (at least legally speaking). A young male of 18 years is considered well into his early adulthood, is hunting with the other adult males and is a fully fledged member of this social group. And yet, his body does not appear to have kept pace. An individual 10 years his senior, who shares the same habitat, whose lineage has experienced the same selective pressures, who endures the same seasonal cycle year in, year out, has at least twice the quantity of body hair.

 

Question: if this fully matured elder male is equipped with this quantity of hair than presumably this is because he needs it. Why is the apparently fully matured younger male not also so equipped at his early age? He is reproductively active, therefore, in natures view, he is fully matured. Why doesn't he grow the hair that natural selection says he needs faster?

 

 

If you think this is a silly question, well, you've just gained an insight into my thought processes whilst staring into the bathroom mirror every morning. Lucky you.

[bombus]

Human evolution has been a process of Neoteny. Basically, this means that youthful features have been selected for over millions of years (why this is so, nobody really knows, but there are a few good theories).

 

The upshot of this is that if an individual human can stay young looking for longer, he/she will have a better chance of producing more offspring than his/her competitors. This is probably more important for females than males, as females have a shorter time limit on reproductive ability.

 

Lack of hair is a neotenic feature.

 

So, humans are now more or less hairless compared to other apes, but we still tend to get hairier as we get older (both males and females) as our ape genes eventually show through despite our evolutionary attempts to suppress them for as long as possible.

 

It's a bit more complicated than this, with other factors playing a part, such as the fact that many females seem to like certain non-neotenic features in their man (e.g. deep voice, tallness, hairy chests) but this is basically the answer.

[Atellus]

Ah! I never thought of that, despite banging on about reproductive activity!

 

Very interesting answer. Thank you.