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Abstract
The natural selection hypothesis suggests that lighter skin colour evolved to optimise
vitamin D production. Some authors question if vitamin D deficiency leads to sufficient
health problems to act as a selection pressure. This paper reviews the numerous effects
of vitamin D deficiency on human health and argues that vitamin D deficiency is sufficient
to pose as a potent selection pressure for lighter skin colour. Vitamin D deficiency
manifesting as rickets and osteomalacia are sufficient to impair reproductive success,
but additionally, animal studies and some clinical observations suggest that vitamin
D may have more direct impact on human fertility. Vitamin D deficiency may lead to
a whole host of clinical conditions which impair health and increase mortality rates:
increase susceptibility to bacterial and viral infections; rickets, osteomalacia and
osteoporosis, with increased risk of falls and fractures; increased risk of cancers;
hypertension and cardiovascular disease; maturity onset diabetes; autoimmune diseases
such as multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease and Type
1 diabetes; and gum disease. We submit that at higher latitudes, lighter skin colour
evolved to facilitate vitamin D production under conditions of low ultra-violet B
radiation in order to avoid a plethora of ill health, reproductive difficulties and
early mortality.