Hairless WomanMark Pagel, head of the evolutionary biology group at the University of Reading in England and editor of The Encyclopedia of Evolution, fills us in:

We humans are conspicuous among the 5,000 or so mammal species in that we are effectively naked. Just consider what your pet dog or cat (or, for that matter, a polar bear) would look like, and how it might feel, if its furry coat were shorn.

Scientists have suggested three main explanations for why humans lack fur. All revolve around the idea that it may have been advantageous for our evolving lineage to have become less and less hairy during the six million years since we shared a common ancestor with our closest living relative, the chimpanzee.

The aquatic-ape hypothesis suggests that six million to eight million years ago apelike ancestors of modern humans had a semiaquatic lifestyle based on foraging for food in shallow waters. Fur is not an effective insulator in water, and so the theory asserts that we evolved to lose our fur, replacing it, as other aquatic mammals have, with relatively high levels of body fat. Imaginative as this explanation is—and helpful in providing us with an excuse for being overweight—paleontological evidence for an aquatic phase of human existence has proven elusive.

The second theory is that we lost our fur in order to control our body temperature when we adapted to life on the hot savannah. Our ape ancestors spent most of their time in cool forests, but a furry, upright hominid walking around in the sun would have overheated. The body-cooling idea seems sensible, but even though lacking fur might have made it easier for us to lose heat during the day, we also would have lost more heat at night, when we needed to retain it.

Read the full article @ Scientific American >>>