In addition to the sex differences in body hair, there exist some marked differences between anthropological groups. These differences may be so strong that the females of some populations are hairier than the males of other groups. Overall, female hairiness increases after the menopause, and in the hairier groups a weak female beard is possible.
With increasing hair development the male beard extends upward on the cheeks, the scalp of the hair begins to extend down on the back of the neck and the beard in the front, hair appears on the arms and legs, particularly the distal segments, and on the chest. The pubic hair can extend upward on the abdomen and finally form a continuous mat up the front of the trunk. In some cases the back becomes hairy, and hair covers nearly the whole body except the palms of the hands and soles of the feet.
The evolutionary reasons for the differences in body hair are not exactly known. Early humans most likely had stronger body hair, and sexual selection reduced hairiness. Additionally, although hair protects the skin, hairy individuals tend to be more vulnerable to parasites.
The least hairy people are found in North Central Asia. Weak body hair may have been an advantage here, because in extreme cold the beard can become encrusted with frozen vapour from the breath, and thereby become a nuisance.
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