-- Mary Elizabeth Dallas
WEDNESDAY, Feb. 26, 2014 (HealthDay News) -- Black skin may have
evolved to protect early humans who lived up to 1.8 million years
ago from skin cancer, a new study suggests.
The British research team bases their theory on data from
today's African pale-skinned albinos -- people with genetic changes
that prevent the production of the skin pigment melanin.
The researchers believe that pale-skinned early humans from
areas of Africa with the highest exposure to the sun's unhealthy
ultraviolet (UV) radiation were under strong evolutionary pressure
to develop darker skin to help shield against skin cancer.
"Charles Darwin thought variation in skin color was of no adaptive value and other investigators have dismissed cancer as a selective force in evolution," lead researcher Mel Greaves, director of the Centre for Evolution and Cancer at the Institute of Cancer Research, in London, explained in an institute news release.
"But the clinical data on people with albinism, particularly in Africa, provide a strong argument that lethal cancers may well have played a major role in early human evolution as an important factor in the development of skin rich in dark pigmentation -- in eumelanin," Greaves said.
Research suggests the evolution of black skin, rich in the
eumelanin pigment that most effectively protects against sun
damage, occurred in early humans living between 1.2 and 1.8 million
years ago in the East African Savannah.
These early humans likely lost most of their body hair to help
stay cooler, revealing pale skin like that of chimpanzees, their
closest relatives, Greaves and colleagues suggested.
Although skin cancer is rarely fatal at ages young enough to
affect reproduction, the study, published Feb. 25 in the
Proceedings of the Royal Society B, revealed that 80 percent
of black people with albinism from African equatorial countries
such as Tanzania and Nigeria, now die of skin cancer before they
reach the age of 30.
There's also an association between albinism and skin cancer
among people in Panama and other tropical countries with high,
year-round UV exposure, the researchers pointed out in the news
The investigators added that increased production of black
melanin could have had other health benefits that helped early
humans pass on key genes to future generations -- DNA that helped
prevent damage to sweat glands or the destruction of folate, a
nutrient critical for fetal development.
Looking ahead, the researchers said they plan to continue their
investigation of human evolution in order to shed light on why
human cancers develop. They will also focus on the development of
drug resistance and the genetic diversity within individual
The U.S. Centers for Disease Control and Prevention provides
more information on the
risk factors for skin cancer.
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