Answer:
Lactose tolerance conferred an evolutionary advantage, thereby this beneficial mutation increased its frequency in the population
Explanation:
Originally, adults were unable to digest lactose. But approximately 8,000-10,000 years ago something remarkable happened: a mutation near the gene that produces the lactase enzyme appeared in a raising cattle population from Europe-Middle East, making adults able to digest lactose. Nowadays, many adults from different societies are tolerant to digest lactose because this mutation increased its frequency and extended to different populations. It is a classical example of how a beneficial mutation may eventually become the most common gene variant by increasing its frequency in the population, and, subsequently extending to other populations. It is possible to hypothesize that new mutations associated with human activities may appear in current human societies, thereby conferring an evolutionary advantage in the same way that lactose tolerance in cattle-raising people. For example, nowadays, mutations in human behavior-associated genes might confer beneficial social skills (thereby increasing the frequencies across time or across populations).
