Human skin pigmentation, migration and disease susceptibility

Jablonski NG, Chaplin G. Human skin pigmentation, migration and disease susceptibility. Philos Trans R Soc Lond B Biol Sci. 2012 Mar 19;367(1590):785-92. 

Human skin pigmentation evolved as a compromise between the conflicting physiological demands of protection against the deleterious effects of ultraviolet radiation (UVR) and photosynthesis of UVB-dependent vitamin D(3). Living under high UVR near the equator, ancestral Homo sapiens had skin rich in protective eumelanin. Dispersals outside of the tropics were associated with positive selection for depigmentation to maximize cutaneous biosynthesis of pre-vitamin D(3) under low and highly seasonal UVB conditions. In recent centuries, migrations and high-speed transportation have brought many people into UVR regimes different from those experienced by their ancestors and, accordingly, exposed them to new disease risks. These have been increased by urbanization and changes in diet and lifestyle. Three examples-nutritional rickets, multiple sclerosis (MS) and cutaneous malignant melanoma (CMM)-are chosen to illustrate the serious health effects of mismatches between skin pigmentation and UVR. The aetiology of MS in particular provides insight into complex and contingent interactions of genetic and environmental factors necessary to trigger lethal disease states. Low UVB levels and vitamin D deficiencies produced by changes in location and lifestyle pose some of the most serious disease risks of the twenty-first century.

“The evolution of skin colour is a very interesting story and the effects migration and social changes are having on our health as a result of our skin colour is becoming increasingly important.”

“Rickets almost certainly drove selection of pale skin when our ancestors migrated out of Africa; woman with rickety or deformed pelvises died in child birth therefore selecting against dark skin colour. Once our ancestors arrived in Europe and more northerly latitudes they got their vD from fish. Now that I diets have changed (less fish or farmed fish), we are doing less outdoor activity (face booking and gaming), wearing make-up with sun block or sun-block period, covering-up for cultural (being pale is beautiful) or religious regions (Muslim woman) our vD levels have plummeted. In addition, increasing air pollution is filtering out more UVB than ever before. What can we do about it? Take vD supplements!”

“Please note that farmed fish has less vD than wild fish. Why? Wild fish get their vD from eating a certain type of plankton; farmed fish who are force feed feed in the form of pellets don’t enough vD in their feed.” 

“This article is a very good read for those interested in the subject.”

One thought on “Human skin pigmentation, migration and disease susceptibility”

  1. As someone who studied Geography (which is absolutely fascinating and doesn't deserve its slightly negative reputation!) I find it really interesting and somewhat gratifying that looking at human migration and patterns of settlement etc can help to give clues in this area of study – if you see what I mean 🙂

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