SAT Reading & Writing · Command of Evidence (textual)
The ability to digest lactose into adulthood is associated with different genetic regulatory variants in European populations compared to…
The ability to digest lactose into adulthood is associated with different genetic regulatory variants in European populations compared to several African pastoralist populations, even though both groups independently developed the same basic ability. A student argues that this shared ability must trace back to a single common ancestral population that passed the trait to both groups. Which finding would most directly undermine the student's argument?
Answer and explanation
Answer: C: The specific genetic variants responsible for adult lactose digestion differ between the two populations, indicating the trait arose through separate mutations instead of being inherited from one…
The student's claim depends on a single shared genetic origin, and C directly refutes that by showing the underlying genetic variants are actually different between the two populations, meaning the same outward trait arose through independent evolutionary paths, not one shared ancestor. A simply restates the shared trait, which is exactly what makes the single-origin theory tempting but isn't itself evidence for or against it. B and D are general background facts unrelated to genetic origin.
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