PrepTest 115, Section 4, Question 18
Foster: Many species of extremely large North American(58 more words not shown)
Which one of the following,(6 more words not shown)
- ASimilar species living(16 more words not shown)
- BMost of the(17 more words not shown)
- CHuman migration to(11 more words not shown)
- DArchaeological evidence reveals(13 more words not shown)
- EThe huge size(16 more words not shown)
Reading the argument
The mammals disappeared around the time humans arrived. Does that mean the humans caused the extinctions? The timing makes Foster's explanation worth considering, but it doesn't establish what killed the animals.
What else was changing? Fisch points to the climate. Perhaps conditions became too harsh too quickly for the mammals to adapt. That is a competing explanation for the same deaths, not a reason to deny that the deaths occurred. It also needs support; we don't know the cause merely because someone offers a different story.
What we’re looking for
The question asks us to strengthen Fisch's climate explanation. I'd look for evidence that the change was especially rapid or severe, making adaptation difficult. Another possibility would be evidence against Foster's explanation—for instance, that the human presence was too limited to account for the losses. Those are directions to investigate, not facts we can assume about the migrants or the climate.
Working the answers
- A
Similar species survived dramatic climate changes elsewhere. That gives us a reason to question whether climate change was enough to account for these extinctions. The comparison might not settle the issue, but it points against the explanation we're trying to support.
- B
This describes mammals that survived and says where and when they migrated. It doesn't tell us why the extremely large species died. We would need another connection—perhaps a difference in their ability to handle the climate—to make the survivors' origins support Fisch's account. B doesn't provide one.
- C
This supports Foster's competing explanation. Human arrivals caused mammal extinctions in other isolated places, so a similar human effect in North America becomes more plausible. It doesn't give us evidence that the climate caused the extinctions at issue.
- D
Large weapons could give the migrants a means of killing large mammals. That doesn't prove they did so, but it fits the human-caused explanation more readily than the climate explanation. We shouldn't turn evidence about the migrants' weapons into evidence about an inability to adapt to weather.
- ECorrect
This takes a different route from simply showing how severe the climate change was: it explains why the mammals had difficulty escaping it. If their large size made migration to milder environments difficult, moving elsewhere was a less effective way to survive the harsher conditions.
That gives the climate explanation a missing practical detail. We might otherwise wonder why the animals didn't move somewhere more suitable instead of remaining exposed to conditions they couldn't adapt to. E makes that escape harder. It doesn't say migration was impossible or prove that climate was the only cause; it makes Fisch's proposed cause more convincing.
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