The international biological program/ human adaptability studies among the

Background: The population is increasingly lighter pigmented moving in a northward direction in Europe until reaching the Arctic Circle, where the Samis (Lapps) are clearly more pigmented. Methods: In 19661970, we investigated a total of 689 subjects in the villages of Sevettijärvi and Nellim, including persons with mixed Sami and Finnish heritage; of these, 487 (242 males, 245 females) had both parents classified as Skolt Sami. For estimation of the colour of the iris and hair, international scales were used. For translucency of the iris, pigmentation of the fundus was estimated in 3 different shades. The length and type of eyelashes were classified into 3 categories. To our knowledge, a simultaneous study of the pigmentation of eyebrows, eyelashes and eye fundus at different ages has not previously been published. Results: The age differences of iris colour were highly significant. Iris colour in children varied markedly, and they generally had lighter colours than later in life. Age and sex effects on the translucency of irises were found. Male irises were more translucent. Fundus pigmentation was scanty in the youngest age groups, with full pigmentation being reached at 20 years. Among young individuals hair colour darkens with increasing age. Eyebrow colour was slightly lighter for both sexes in the youngest age groups that in older cohorts. Women had longer eyelashes than males. Conclusions: The main factor of the lighter skin is a higher ability to synthesize vitamin D, providing superio