Passage Summary: A biologist argues that goats on islands don't get smaller just to help the whole group survive; they only get smaller if being small actually helps an individual goat have more babies.

Reasoning: No reasoning (Fact Set).

Analysis: The biologist is rejecting a 'group selection' theory—the idea that traits evolve for the good of the species—in favor of 'individual selection,' where only reproductive success matters. We are looking for a statement that must be true if the biologist's rule is absolute. If the biologist is right, then any trait that doesn't help with individual reproduction won't become more common just because it helps the species as a whole. Look for an answer that reinforces this strict link between individual reproductive success and the frequency of a trait.