Passage Summary: Some researchers argue that animal extinctions aren't actually speeding up, but the author disagrees, citing data that shows North American fish extinctions more than doubled in the second half of the last century.

Conclusion: The claim that there is no evidence of an accelerating extinction rate for animal species is incorrect.

Reasoning: In the twentieth century, 40 North American fish species went extinct, with significantly more extinctions occurring between 1950 and 2000 (27) than between 1900 and 1950 (13).

Analysis: To evaluate this argument, we must bridge the gap between a very specific data set—North American fish—and the broad conclusion regarding all animal species globally. The author is essentially trying to win a global debate by pointing at one specific neighborhood's fish tank, so we need to know if fish are actually representative of the animal kingdom at large. Furthermore, we should consider if our ability to detect extinctions improved after 1950; if we simply became better at noticing when fish went missing, the 'acceleration' might just be a byproduct of better record-keeping. Look for an answer choice that questions the representativeness of the fish data or the consistency of the data collection over time.