ARCH 131 Lecture Notes - Lecture 5: Vitamin D Deficiency, Folk Taxonomy, Genetic Drift
15 Jun 2017
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Document Summary
A polygenic, polymorphic trait, determined by up to 6 loci. Actually far more variable interregional than most other genetic markers. Dark skin is protective at low latitudes. Vitamin d is important for bone formation. At least two high-latitude populations have depigmented skin (northern europe; northeast. People with deeply pigmented skin sometimes have low vitamin d in high latitudes. Some low-latitude populations have lighter skin; some high-latitude ones have darker skin. Access to fish & sea mammals may be a factor. Some mesolithic european humans (7000bp) had deeply pigmented skin. Rickets (vitamin d deficiency) wasn"t common before the industrial revolution. Depigmentation (pale skin) is probably a recent adaptation. Geographical distribution of skin colour reflects drift and selection. Multiple selective factors may have been at work: We are variable in size, shape, colour (phenotype) We are widespread so variation is geographically structured. Some phenotypic variation is adaptive (solves a fitness problem shaped by selection)
