Lactose tolerance (also known as lactase persistence) allowed humans in certain regions of the world to flourish (that is survive and reproduce) because they could digest diary products as adults in areas where food was scarce.

Question

BlackTom AI · Accepted Answer

Lactase persistence is the continued production of the enzyme lactase into adulthood, which allows digestion of lactose, the sugar in milk. This trait is a genetically based adaptation (most commonly due to regulatory mutations affecting the LCT gene) that became common in human populations that practiced dairying. It is an example of gene-culture coevolution: the cultural practice of domesticating ruminants and consuming their milk created a selective environment favoring alleles that confer lactase persistence.

Step-by-step reasoning:
1. Biological basis and variation: Most mammals downregulate lactase after weaning; humans show population-level variation. Specific mutations in regulatory regions keep the lactase gene active in adults.
2. Selective advantage in dairying societies: In environments where pastoralism arose (e.g., northern Europe, parts of East Africa), milk provided a reliable source of calories, protein, fat, calcium, and fluids, especially during seasonal food shortages or famines. Adults who could digest milk could exploit this resource directly.
3. Fitness consequences: Access to extra nutrients increases individual survival probability during scarcity and can improve reproductive success (better nourishment for mothers and offspring, higher child survival), so lactase-persistent alleles increased in frequency by natural selection.
4. Corroborating evidence: High frequencies of lactase persistence correlate with archaeological and genetic evidence of long-term dairying. The rapid spread of persistence alleles in some regions fits a model of strong positive selection.

Why the correct answer is True: The presence of lactase persistence enabled adults in certain regions to consume and extract nutritional benefit from dairy products when other food sources were limited, improving survival and reproduction—criteria for natural selection to favor the trait.

Why “False” would be incorrect: Saying lactase persistence did not confer such an advantage ignores the clear archaeological, genetic, and nutritional evidence linking dairying, selection for lactase persistence, and greater fitness in certain environments.

Final confirmation: The correct answer is True.

Lactose tolerance (also known as lactase persistence) allowed humans in certain regions of the world to flourish (that is survive and reproduce) because they could digest diary products as adults in areas where food was scarce.判断题

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