When the first hominins (human ancestors) began hunting and gathering on the open savannah, they lost their body hair, likely to keep cool amid the strenuous exercise of their lifestyle. These early humans probably had pale skin, much like humans closest living relative, the chimpanzee, which is white under its fur. Around 1.2 million to 1.8 million years ago, early Homo sapiens evolved dark skin. But evolutionary biologists havent been convinced that skin cancer itself drove the evolutionary change. (Light skin evolved again after humans moved out of Africa to higher latitudes.) Thats because skin cancer in the modern world tends to strike later in life, after the reproductive years. From an evolutionary perspective, this time not very important. What really matters is survival during the reproductive years in order to pass on genes to offspring. ... So researchers have come up with alternative reasons that dark skin might promote survival. Possibilities include avoiding painful sunburns, which would prevent effective hunting and gathering; improving vision, because a lack of pigment comes with vision problems; protecting the sweat glands from sun damage; and protecting the bodys supply of folic acid, which is crucial for neural development and which can be damaged by excessive ultraviolet (UV) radiation from the sun.
Posted on: Thu, 13 Mar 2014 15:06:10 +0000
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