Final answer:
The commonality of lactose tolerance in European populations is evidence of evolutionary adaptation, influenced by dietary changes due to dairy farming. Vitamin D absorption and new selection pressures from a grain-based diet are other factors linked to this genetic evolution. Asian populations have a higher prevalence of lactose intolerance, showing diverse evolutionary paths.
Step-by-step explanation:
The persistence and commonality of lactose tolerance in European populations provide evidence of an evolutionary adaptation. The lactase persistence trait allowed for the digestion of lactose in adult life, conferring a nutritional advantage in regions where dairy products were available. This nutritional advantage likely contributed to the spread of the gene among populations, especially where dairy farming and the consumption of milk and other dairy products became prevalent and important for survival, as seen in European cultures.
Further factors that may have affected this adaptation include the ability to absorb vitamin D, which in climates with less sunlight, like in Europe, could be gained through the consumption of dairy products rich in this vitamin. Additionally, the introduction of a grain-based diet during the agricultural revolution introduced new selection pressures which may have influenced human genetics and adaptations like lactose tolerance and tooth decay from increased carbohydrate intake.
In contrast, regions such as Asia have a high prevalence of lactose intolerance, with up to 65 percent of humans being unable to digest cow's milk. This indicates a different evolutionary path, where the lack of domesticated dairy animals or cultural dietary preferences may have influenced the persistence of lactase production into adulthood.