No, that’s not a climatic adaptation (actress Lily Cole - source) “European skin turned pale only recently�—such was the headline in Science five years ago. The report had been presented by a postdoc, Heather Norton, at the annual meeting of the American Association of Physical Anthropologists (Norton & Hammer, 2007). Over the following years, I... Read More

Annual average exposure to erythema-inducing UV radiation at ground level. Source: Jablonski & Chaplin, 2000. At high northern latitudes, vitamin D can be obtained only from one’s diet, notably fatty fish. Yet many northern native peoples consume little fish. Have they evolved a different vitamin D metabolism? I’ve just published an article on population differences... Read More

Drinking from the wrong chalice? By his mid-40s, Michael Jackson had skin like parchment. The end of 2010 is drawing nigh, and the time has come to review my predictions from last year. Brain growth genes Back in 2005, it was found that human populations vary considerably at two genes, ASPM and microcephalin, that control... Read More

Above - Artist's reconstruction of pre-Viking Age boat Below – Prehistoric rock paintings of boats (Scandinavia) Some writers argue that European skin became white to offset a decline in dietary vitamin D. Pre-agricultural diets, however, were rich in vitamin D only among coastal Europeans who consumed fatty fish. The ‘vitamin D hypothesis’ is often invoked... Read More

This year, look for advances in the following areas: Brain growth genes Back in 2005, it was found that human populations vary considerably at two genes, ASPM and microcephalin, that control the growth of brain tissue. The finding seemed to be ‘huge’ in its implications. Then, it all fizzled out. No correlation could be found... Read More

It’s well known that African Americans have low levels of vitamin D in their blood. In fact, this seems to be generally true for humans of tropical origin. In a study from Hawaii, vitamin D status was assessed in healthy, visibly tanned young adults who averaged 22.4 hours per week of unprotected sun exposure. Yet... Read More

Why are Europeans so pale-skinned? The most popular explanation is the vitamin-D hypothesis. Originally developed by Murray (1934) and Loomis (1967), it has been most recently presented by Chaplin and Jablonski (2009). It can be summarized as follows: 1. To absorb calcium and phosphorus from food passing through the gut, humans need vitamin D. This... Read More

The English, like other Western nations, were once plagued by rickets—a softening of the bones leading to fractures and deformity, particularly in children. Initially rare, it became much more frequent after 1600 and had reached epidemic levels by the turn of the 20th century (Gibbs, 1994; Harrison, 1966; Holick, 2006; Rajakumar, 2003). A survey at... Read More

In my previous posts, I argued that a homeostatic mechanism keeps the level of vitamin D in our bloodstream within a certain range. When UV-B light is always intense, as in the tropics, the level seems to be 50-75 nmol/L in young adults and progressively lower in older age groups. The more sunlight varies seasonally,... Read More

How can vitamin-D deficiency exist despite lengthy sun exposure? This apparent paradox was raised in my last post. The medical community now recommends bloodstream vitamin D levels of at least 75-150 nmol/L, yet these levels are not reached by many tanned, outdoorsy people. In a study from Hawaii, vitamin D status was assessed in 93... Read More

In the late 19th century, a major concern was the poor health of industrial populations, particularly in England but also in other Western countries. The cause? For the medical profession, it seemed to be lack of sunlight. In densely packed tenements under the pall of factory smoke, not enough sunlight was getting through to kill... Read More

Is white skin an adaptation to the cereal diet that Europeans have been consuming for the past five to seven thousand years? When early Europeans switched from hunting and gathering to cereal agriculture, the new diet may have provided less vitamin D (i.e., from fatty fish), which the body needs to metabolize calcium and create... Read More

Differences in human skin color are commonly explained as an adaptive response to solar UV radiation and latitude. The further away from the equator you are, the weaker will be solar UV and the less your skin will need melanin to prevent sunburn and skin cancer. A variant of this explanation involves vitamin D, which... Read More