Hairlessness or Nakedness in Humans

I did not attend last night's meeting (I had reserved a table so I hope that was set up when you got there!) but I wanted to offer my opinion on the paper suggested by Brad. I agree with the author in that many of the previously proposed hypotheses for human hairlessness are not supportable. Hairiness is often painted as a means of keeping warm and rarely viewed as a means of keeping cool. Of course when we think about hair functions, this makes perfect sense. Hair takes advantage of the insulating properties of air by trapping it next to the body so it follows that the body should also be cooler than ambient temperature in savannah ecosystems. I think the least realistic hypothesis is the aquatic ape hypothesis. As the author mentions, many aquatic or semiaquatic mammals retain hair (again because of the insulating properties of air). These include things like beavers and otters. One thing the author doesn't mention is that hairless aquatic mammals also tend to have a high amount of insulating blubber to protect them from the cooling effects of water. But I would also expect an aquatic ape to have features more appropriate for swimming. As humans, we are terrible swimmers (perhaps not as terrible as ungulates with their spindley legs). I also agree that it is hard to separate the effects of sexual selection from the effects of natural selection but, as the author mentions, there had to be an initial impetus for hair loss or reduction.

It is clear from the paper that the author favors the parasite hypothesis. In essence, apes began to lose their hair because of increased parasite loads resulting from living in dens as a group. I didn't go to the original paper that is cited but this sounds initially convincing. I do wonder, however, about other den living animals (that also live in groups) that have retained their hairiness. I can think of a few of these animals including meerkats and burrowing rabbits. Are the insulating properties of the fur more important than the selective pressures placed upon them by increased parasite loads? In general, I don't find the parasite hypothesis satisfying and feel that the question of human nakedness is far from answered.

I am interested in seeing what came out of the discussion yesterday as well.