Final answer:
Infants have more lactase, enabling them to better digest lactose, whereas most adults produce less of this enzyme, leading to lactose intolerance in many cases. Some human populations have adapted to maintain lactase production into adulthood.
Step-by-step explanation:
Based on the information provided, one can infer that infants are more able to break down lactose in milk due to the presence of the enzyme lactase. This enzyme is responsible for the hydrolysis of lactose into glucose and galactose, which are then absorbed in the small intestine. Most adults, on the other hand, have a reduced ability to produce lactase and therefore may experience lactose intolerance, causing symptoms like bloating, cramps, and diarrhea when consuming dairy products. In some populations, however, the ability to produce lactase persists into adulthood, a trait that is believed to be a result of evolutionary adaptations related to diet and nutrition.