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Question

Difficulty: EasyIdentifying Implicit or Unstated Main Ideas

Genetic analysis of ancient skeletal remains has revealed that for the vast majority of human history, the enzyme lactase—which breaks down the sugar in milk—deactivated after infancy. However, approximately 10,000 years ago, a genetic mutation emerged that allowed lactase production to persist throughout adulthood. This mutation arose alongside the development of early dairy farming in Europe and Africa. In communities where cattle domestication became central to survival, individuals who could digest milk had a major nutritional advantage, especially during periods of crop failure. As a result, this genetic variation spread rapidly through these pastoralist populations. Today, adult lactose tolerance is highly concentrated in populations with ancestral ties to dairy farming, while it remains rare in regions where ancestral societies relied solely on agriculture or hunting.

Which of the following best expresses the central theme of the passage?

  1. A
    Adult lactose tolerance is a universal trait that developed before humans began domesticating animals.
  2. B
    The mutation for lactase persistence first emerged around 10,000 years ago in Europe and Africa.
  3. Human genetic evolution has been directly influenced by cultural practices like dairy farming.Answer
  4. D
    Dietary habits and genetic traits have always played a critical role in the survival of human civilizations.

Answer

Human genetic evolution has been directly influenced by cultural practices like dairy farming.
The correct answer shows that human genetic evolution was directly shaped by cultural practices. The passage supports this by demonstrating that the genetic mutation for adult lactase persistence became widespread precisely because of the survival advantages of dairy farming in pastoralist societies.

Step-by-Step Solution

1
Analyze the passage's subject matter and focus.
The passage discusses the origin of adult lactose tolerance (lactase persistence) and its correlation with dairy farming history.
Understanding the topic helps separate key arguments from minor details.
2
Identify how the details connect to a larger, unstated point.
The text links the genetic mutation for digesting milk to the cultural practice of farming cattle, showing that populations with this culture evolved to keep producing lactase.
Connecting cultural practices with genetic changes reveals the implicit thesis.
3
Evaluate the choices to find the one that best captures this central relationship.
The statement about cultural practices directly shaping genetic evolution summarizes this relationship, whereas other options are either too broad, too narrow, or incorrect.
Selecting the most accurate and comprehensive option yields the correct answer.

Key Concept

Identifying Implicit or Unstated Main Ideas
Estimated Time:1m 30s
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Topics

Identifying Implicit or Unstated Main Ideas

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