Passage Summary: Two people are arguing about why big animals in North America died out; one blames humans, but Fisch blames a sudden, harsh change in the weather.

Conclusion: The extinction of large North American mammals was caused by a rapid shift to a harsher climate rather than human migration.

Reasoning: The climate changed so quickly during the last ice age that these species were unable to adapt to the new, harsher conditions.

Analysis: To strengthen Fisch's argument, we need to bolster the climate change theory or weaken the human migration theory. A great way to do this would be to provide evidence that the extinctions occurred in a pattern that matches climate shifts better than it matches human movement. For example, if extinctions happened in areas before humans arrived, or if similar extinctions occurred in regions where humans never migrated, Fisch's position becomes much more plausible. We are looking for an answer that provides that extra bit of empirical support for the climate-death link.