Final answer:
Adult humans need the enzyme lactase to digest milk. Lactose intolerance occurs when there isn't enough lactase produced, causing digestive discomfort when consuming dairy. Certain populations have a mutation allowing for continued lactase production into adulthood.
Step-by-step explanation:
The ability of adult humans to digest milk is dependent on the production of an enzyme known as lactase. This enzyme is crucial for hydrolyzing lactose, the sugar found in milk, into glucose and galactose, which can then be readily absorbed by the small intestine. In many adult mammals and humans, the production of lactase decreases after weaning, leading to lactose intolerance. However, certain human populations have developed a genetic mutation allowing for the continued production of lactase into adulthood, which is particularly common among Europeans due to the evolutionary advantages it provided in the past.
Lactose intolerance is an inability to digest lactose due to insufficient production of lactase and is characterized by symptoms such as bloating, cramps, and nausea. For those who are lactose intolerant, alternatives such as lactose-free milk or lactase supplements can help mitigate these effects, allowing them to consume dairy without discomfort. The discussion of lactose intolerance and its genetic basis also sheds light on broader themes of human adaptation and food culture.