Question

Humans are unusual because our cultural practices can actually change our environmental circumstances. We can change the environment in which natural selection acts on our traits. Describe how this process has played out in the evolution of adult lactose tolerance. Describe how this process has played out in the maintenance of the sickle-cell trait. Can you hypothesize any similar situations where our future evolution may be influenced by cultural practices we have today

Answer 1

Adult humans capable of digesting lactose were selected, thereby this phenotypic trait became common in dairy consuming societies

Explanation:

From the first moment after birth, babies can digest lactose in milk because they produce lactase, which is an enzyme capable of hydrolyzing lactose into glucose and galactose. In human societies that non consume milk products, the level of the lactase enzyme abruptly decreases during the first years of life due to the inactivation of the gene encoding this enzyme (i.e., lactase gene). However, in dairy consuming societies, a genetic mutation in the lactase gene that appeared among early cattle-raising people in Europe was selected, nowadays, this mutation is mostly present (i.e., in a higher frequency) in these societies, thereby adult people is generally adapted to consume lactose-based products.