Describe briefly 3 hypotheses regarding the variation in lactase activity

Describe briefly 3 hypotheses regarding the variation in lactose activity Here

1. Adults who could digest lactose were at a selective advantage over those who could not during the coevolution of pastoralism and milk consumption (gene-culture coevolution)
2. In high latitude populations in Europe sunshine is limited and there is an increased risk for Vitamin D deficiency. The major source for Vitamin D is exposure to sunshine (converts a pro-hormone in the body to vitamin D which is required for bone growth and development). When sunshine is not available lactose in fresh milk promotes the uptake of calcium and thus promotes normal bone growth.
3. In arid environments individuals with lactase persistence would be able to make better use of the water content in milk thus increasing their chances of survival.