Final answer:
Lactase persistence is often a result of genetic adaptation in human populations where dairy consumption provided a nutritional advantage. Multiple independent genetic mutations have led to this trait, which allows for continued digestion of lactose into adulthood. Lactose intolerance, by contrast, occurs when there is a deficiency of lactase, leading to indigestion caused by dairy products.
Step-by-step explanation:
The possible causes of Lactase persistence, which is the continued production of the enzyme lactase into adulthood, primarily stem from genetic adaptation. Unlike other mammals that typically lose lactase expression after weaning, some human populations have evolved to maintain lactase production. This genetic adaptation is believed to be a result of dietary practices—specifically, the domestication of dairy animals and the consumption of their milk. The maintenance of lactase production allows for the digestion of lactose, the sugar found in milk, which provided a nutritional advantage in certain cultures, particularly where milk became a substantive part of the diet.
The ability to digest milk gave a significant evolutionary advantage due to the additional nutrients and the ability to consume unspoiled milk as a water source, which may have led to an increased survival rate and reproductive success. This lactase persistence is most notably found in populations with a long history of pastoralism, such as those in Europe and some African tribes. Genetic mutations responsible for lactase persistence are different among various populations, suggesting multiple independent mutation events—also known as convergent evolution.
As for lactose intolerance, this condition is characterized by the insufficient production of lactase, leading to discomfort when consuming dairy products. Lactose intolerance can be diagnosed through tests like the hydrogen breath test. The condition is managed by avoiding lactose-containing foods or by taking lactase enzyme supplements.