In passing it may be noted that the need to retain sweat on near-vertical surfaces has led to morphological adaptations in addition to the physiological ones. The features of the face may be explained in part by the need for platforms to check, and hair tufts to catch, the descending sweat drops generated from the gland-rich scalp, a specialized heat-dissipating organ. Hence supraorbital tori, flared nostrils, everted upper lip, a chin (a late development in our evolutionary history) and hair remnants such as eyebrows and moustache. Sternal and pubic helical hair serve the same function. Pubic hair extends up the central abdominal gutter in the male to meet and trap the descending sweat drops; endomorphic females have no central gutter and the superior surface of the pubic hair is thus horizontal.

We now know that whales evolved from a common ancestor with hippos and likely developed hairlessness independently of aquaticness.

Is it possible ( and in my mind at least as a hairy bastard) that hair serves the male for purposes of territorial signature? A scenting mechanism?

It seems likely in light of the human “system of subcutaneous fat and enhanced circulation through and above it that allows heat loss without interference from the insulating fat.”

Where there’s fat there’s fire, or in this case sweat–odorous sweat–malodorous sweat if left in a natural state.
Not that I am trying to be confessional or anything…

The dates: This NYT news story by Nicholas Wade on the date of hair changes (reprinted at headlice dot org — really) covers it all pretty nicely. The date for the loss (actually more accurately big change rather than loss) of body hair is about 1.8 mya (and I regret I don’t have handy the range that should be in this date, as that’s always important to remember and tends to get lost in news story and general retelling). And then the recolonization of body hair by head lice is where the date for wearing clothing comes in, and that’s given as 72,000 years ago although the range is something like 70,000-120,000 years ago, if I’m remembering correctly.

This is a bit of a pet peeve, the way the range in these studies gets turned into a definite number; there’s always a range in the result from a molecular study. Another pet peeve about human hair specifically is the way we call it hairlessness rather than what it is, which is a big change in body hair length and thickness. I think these things are ultimately important because thinking about how something happened requires we be accurate about what actually did happen — GIGO.

The “radiator hypothesis” does fit the facts about what human body hair is like. But it doesn’t get into the sexual selection part of the feature, and human body hair is either a classic case of sexual selection or something that somehow mimics sexual selection exactly. My site has stuff on this if you’d like to get into it more, but the bottom line is that when you see a feature that varies between peoples, varies radically between the sexes and changes radically exactly at puberty you had better be thinking sexual selection. This is likely also the reason behind public hair, underarm hair, and probably part of the beard question. Scent glands, since we find sebaceous glands in these places, which are also another thing that bears the classic hallmarks of sexual selection, plus being more prevelant in males while females have better scent receptors. Coincidence? Sure. 🙂

Beards probably also have a “power” “bulk” exaggerate size” component, which is a common sexual selection thing too.

As for the aquatic ape idea, my site has an awful lot on why it doesn’t make sense and I won’t try to repeat it here, but let me point out that although the idea’s proponents have for some time now been trying to make the claim that they’re just talking about some waterside rambling and a bit of wading, swimming, and diving, this actually makes their idea even less sensible. The basic problem is that they claim we got the way we did (and they are inaccurate about the features they’re talking about, so they commit the GIGO error) via water use, and the features they claim for us are the features of a very few fully aquatic mammals which have been fully aquatic for tens of millions of years. It never made sense that a few million years of semi-aquaticism gave us those features, but it makes even less sense when you lessen the amount of water use.

The Vernon Reynolds quote mentioned certainly makes sense if you’re talking about humans being able to swim and dive, but that’s not the aquatic ape theory; that’s just regular old human evolution. We can swim and dive pretty well for a primate, about as well as your average macaque, the hairy little buggers. True, the average untrained human can’t hold their breath as well as the average dog, but we manage.

Whatever the case is I think itâ??s great that human beings have evolved to have less body hair.

Exactly. Imagine if we hadn’t — we’d all be going around complaining about how unfair it was that evolution hadn’t eliminated all that hair and dealing with the lack of attractive (hairless) mates.

Then there’s the problem of what would have cropped up in place of the Furries — Skinnies? Who knows? That’s a problem for Bill Holbrook to work, I suppose.