Final answer:
Lactose intolerance is the inability to digest lactose due to a lack of the enzyme lactase. It is believed to be a result of natural selection. In populations where dairy farming was prevalent, individuals who had a genetic mutation allowing them to produce lactase as adults had a survival advantage.
Step-by-step explanation:
Lactose intolerance is a condition characterized by the inability to digest lactose, the sugar found in milk. It occurs when the body lacks the enzyme lactase, which is needed to break down lactose. This condition is thought to be a result of natural selection.
In regions where dairy farming was not prevalent, there was no selective pressure for individuals to continue producing lactase into adulthood, as the consumption of milk was not common. However, in populations where dairy agriculture was practiced, individuals who had a genetic mutation that allowed them to continue producing lactase as adults had an advantage. This advantage allowed them to consume milk and obtain its nutritional benefits, which included a valuable source of calcium, proteins, and vitamin D.
Over time, these individuals were more likely to survive and reproduce, passing on the lactase-persistent gene to future generations. This is an example of how natural selection can lead to the development and prevalence of lactose tolerance within certain populations.