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Q J Med 1999; 92: 418
© 1999 Association of Physicians
Correspondence |
Pigmentation, melanocortins and red hair
The Nairobi Hospital,Nairobi
Sir,
Rees and Flanagan in their Editorial `Pigmentation, melanocortins and red hair' (QJM 1999; 92:125–31) make a number of asides. They write `Melanoma may be the evolutionary price paid for protection against burning'. The fact is that Africans, best protected from sun rays, do not have melanoma on pigmented skin, their melanoma is typically on their (unpigmented) feet, where it used to be much more common before they began to wear shoes. White horses as well as greys do develop melanoma, as do red-haired dogs. Red hair is not a mainly Irish-Welsh attribute and not a `Northern' characteristic. One can find numerous red-haired people in Sicily and Calabria, and it is said that the Phoenicians had red hair.
The mechanisms selecting for pigmentation among mammals and birds are confusing. That forest dwellers benefit from dark colour may be easy to comprehend. Melanism at altitude may relate to forests. But why should there be melanistic buzzards and egrets?
Red-haired women have had a reputation of being lascivious, have been accused of witchcraft, but also have been considered to faint easily and to be difficult to anaesthetize. Perhaps this is prejudice, discrimination. Perhaps such traits, (including witchcraft?) are coded for.
A word on sebum. Dark-skinned people produce great qualities of sebum so that their skin shines. Hence they do not absorb all the incident radiation, in this way they have to expend less energy on maintaining core temperature. The tendency to form keloids may be the evolutionary price for abundant sebum ...
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