Final answer:
Lactase persistence allows certain adults to produce lactase continuously, enabling them to digest lactose found in milk. This trait is considered an evolutionary adaptation related to the domestication of dairy animals and has nutritional benefits. It contrasts with lactose intolerance, which causes digestive discomfort due to insufficient lactase production.
Step-by-step explanation:
Lactase Persistence in Humans
Lactase persistence refers to the ability of some adults to continue producing the enzyme lactase throughout their lives, which is necessary for the digestion of lactose, the sugar found in milk. Normally, many mammals, including humans, reduce the production of lactase after weaning, leading to lactose intolerance. However, certain human populations have developed lactase persistence, allowing them to continue consuming milk products into adulthood without discomfort. This is believed to be an evolutionary adaptation.
The mechanism behind lactase persistence involves the regulation of the gene responsible for lactase production. In lactase persistent individuals, this gene remains active, whereas it typically turns off in those who are lactose intolerant. The evolutionary basis for lactase persistence likely stems from the domestication of dairy animals and the nutritional advantages gained from being able to digest lactose as an adult. Cultures with a history of dairy farming and milk consumption over thousands of years have higher rates of lactase persistence, suggesting a strong selective advantage for those with this trait.
Lactose intolerance results from insufficient production of lactase leading to digestion problems when consuming dairy products. This condition can cause bloating, abdominal cramps, and diarrhea, as undigested lactose is fermented by bacteria in the colon. By contrast, lactase persistence allows for the proper digestion of lactose, offering a valuable source of nutrition and energy.