Re: Why has the species homo sapiens lost most of its fur/hair?

Within the realm of evolutionary biology, the topic of human origins per se is extremely specialized. Thus, be aware that I speak as an evolutionary ecologist, not a specialist in human origins. If my explanation seems too tenuous or incomplete, I can work with you to get your query re-submitted in an attempt to find a specialist in the field of human origins.

Also, please realize that there is plenty of room for theory and rather a paucity of hard evidence in the field of human origins. Thus, you're most likely going to have to live with theory -- not hard fact -- even if you do contact a specialist in human origins.

My best shot:

concept #1: Traits may proliferate without having an adaptive advantage. If a trait is adaptively neutral, it may proliferate literally by random chance. If you are familiar with the concept of genetic drift -- which occurs to *some* extent in all populations, not just small ones -- this will be immediately apparent. It just takes longer in larger populations. Also, adaptive advantage is *always* dependent on the organism in which the environment lives. If you consider the climate in the areas of Africa &/or Middle East where homo sapiens might have originally evolved, the fur coat really might not have been an advantage at all....

concept #2: It has been theorized that part of the transition from our ancestral state to our current state is, at least partially, a manifestation of NEOTENY -- the retention of juvenile characteristics in the (sexually mature) adult. If you consider the relative body proportions (or allometry), you can see that primate heads are a larger percent of total body mass in younger individuals. Homo sapiens is the extreme example of this relationship, but also homo sapiens has the largest brain:body ratio as an adult as well. The latter part is the specific example of neoteny. Note also that hairlessness is an extreme juvenile characteristic in some mammals. (I do not know if this is true for chimpanzees, but it would be worth checking into, as they are our closest existing evolutionary relatives.) Because the evolution of neoteny is driven by selection on alleles (genes, loosely) which govern developmental timing & cadence, it is entirely possible that the hairless condition was a by-product of the developmental changes which favored the retention of the proportionally larger cranial capacity.

I hope this helps. Feel free to write more directly to me if you would like further discussion on this or related topics. I believe the theory re: neoteny was originally put forth by Stephen J. Gould; you could look for his work at you local library or amazon.com (or its British equivalent). Other key words & phrases to investigate further: genetic drift; adaptive topoography (Sewell Wright, I think, brought this phrase into use); neoteny; allometry; Irish Elk; heterochrony.

Cheers! Eric entfolks@mwci.net
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