LSAT 119, Section 1, RC Passage 3, Pronghorn

RC Passage 3 Explanation

PASSAGE TEXT: The pronghorn, an antelope-like mammal that lives on the western plains of North …

Paragraph Summaries

1. The pronghorn is extremely fast even though no current North American predator is fast enough to catch it. One explanation is that its speed evolved to escape predators that went extinct thousands of years ago, such as American cheetahs and long-legged hyenas.
2. Biologists are usually skeptical of explanations based on “relict behaviors”, i.e. traits that remain after the original reason for them disappears, because they are difficult to test. They usually only consider these explanations when other explanations do not work.
3. Evidence supports the idea that pronghorns have adaptations from extinct predators. Their herd behavior, despite having little need to avoid current predators, may have developed for protection against past threats. Their mating behavior also supports this because females choose males based on speed and endurance, suggesting these traits were once important for survival.
4. Other animals also show behaviors that appear to be leftovers from extinct threats. Some fish still react defensively to predators they no longer encounter, and some squirrels still fear snakes that disappeared long ago. However, these behaviors eventually fade when animals have been separated from the threat for extremely long periods.

Analysis

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