quote:
The hairlessness of humans is one instance, there's been a lot of debate about that.
Greetings all,
I would like to take a stab at this from a natural selection perspective. It may be completely wrong, but it is most certainly testable.
Why are humans the only generally hairless primates? One correlation is that human beings are the only bipedal primates. Note that hair is still found in hot spots, such as the head (most heat is lost from the head), the armpits, and the groin. Hair loss could very well be a balance between energy gain/energy loss, or conservation of energy. The fossil record shows that homonid evolution occurred in hot areas. The constant production of hair is certainly expensive in terms of calorie usage. If an organ or feature becomes relatively useless, a reduction can occur in a population because maintaining it wastes so much energy.
In a hot desert climate hair is an excellent radiator. I watched an athlete running on a treadmill through an infrared video on TV, and when the runner was really heated up, you could easily make out his hair line. Wherever there was hair on the head, it was effectively radiating the excess heat. A plausible reason why humans still have hair in the hot spots is because the body needs radiation in these areas to run more efficiently. Too hot is bad.
This explanation explains why humans are the only primates relatively hairless and it also explains why our hotspots still have hair. It also conforms to the fossil evidence. This explanation could be entirely wrong, but since it is a natural explanation it can be tested.
best,
Edited by Jeff Davis, : No reason given.
Edited by Jeff Davis, : No reason given.
Edited by Jeff Davis, : No reason given.
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