Final answer:
Lactose tolerance in humans evolved as a genetic mutation that gave lactase-persistent individuals in certain populations, like Europeans, an evolutionary advantage. This adaptation allowed better digestion of dairy products, providing essential nutrients such as calcium and vitamin D, and it spread through reproduction. Prebiotic adaptation and modern alternatives like lactose-free milk also facilitate the consumption of dairy for those with lactose intolerance.
Step-by-step explanation:
Lactose Tolerance Evolution
When humans began drinking milk, the development of lactose tolerance was influenced by genetic mutations in combination with dietary needs. Initially, the vast majority of humans were lactose intolerant after weaning, similar to other mammals, as they lacked the enzyme lactase needed to metabolize lactose. However, in regions like Europe, where dairy became a significant part of the diet due to the domestication of cattle, certain individuals with a genetic mutation that allowed them to continue producing lactase into adulthood had a survival advantage, particularly in environments where vitamin D was scarce.
This mutation conferred the ability to digest lactose, leading to less morbidity from ailments like those of milk poisoning and an increased capability to absorb nutrients, like calcium and vitamin D, from dairy products. Over time, these lactose-tolerant individuals were more likely to survive and reproduce, spreading the trait through the population. In modern times, processed dairy products like cheese or yogurt, which can be tolerated by many who are lactose intolerant, have become a valuable source of nutrition, further embedding dairy practices in culture.
Prebiotic adaptation also plays a role in the development of lactose tolerance, where the microbes in the intestine change to aid in the digestion of lactose despite the host's genetic predisposition. Moreover, foods such as lactose-free milk and lactase supplements have made it possible for lactose-intolerant individuals to consume dairy without discomfort.