PrepTest 149, Section 4, Question 2
When the ancient fossils of a primitive land(58 more words not shown)
Which one of the following,(7 more words not shown)
- AThe unearthed land(15 more words not shown)
- BThe recently discovered(12 more words not shown)
- CThe site at(17 more words not shown)
- DCountries with rich(15 more words not shown)
- ESome other island(19 more words not shown)
Reading the argument
Were the mammals still there when the birds became established?
Finding a fossil establishes that a mammal once lived in New Zealand. It doesn't establish that the mammal competed with the bird population we're trying to explain. Imagine the mammals dying out, leaving an island where the birds later develop without that competition. The fossils and the proposed explanation could both fit that history.
What we’re looking for
That's the timing I'd want a weakener to address. The author treats evidence of mammals at some point in the past as enough to reject an explanation based on their absence. Show that the mammals were gone during the relevant period, and the discovery no longer defeats the theory.
Working the answers
- A
More ancient mammals don't resolve whether they overlapped with the birds. Several mammal species could all have disappeared before the bird population became established. Their existence therefore doesn't supply the timing that would make this discovery contradict the theory—or the absence of overlap that would directly weaken the author's rejection.
- BCorrect
The mammal died out long before the bird population was established. So its ancient presence doesn't show that the birds faced competition from it while their population developed. The author can no longer use this fossil as evidence that the proposed absence of competition was false. B doesn't prove the theory; it removes the discovery's supposed conflict with it.
- C
Reptiles and insects are different animals from the mammals at issue. Finding their fossils at the same site doesn't tell us whether the land mammal lived alongside the relevant bird population. Nor does it establish how those other species affected the birds. The crucial timing question remains unanswered.
- D
This broad pattern could fit the idea that abundant mammals and abundant birds don't go together. But it doesn't directly address why this particular ancient mammal disproves the explanation for New Zealand. We still wouldn't know whether the mammal and the birds overlapped. B supplies that missing historical fact instead of a comparison across other countries.
- E
A mistaken belief about other islands' mammal histories doesn't settle New Zealand's history. Those islands might have different timelines and different bird populations. We need to know whether the newly discovered New Zealand mammal actually interferes with the explanation being rejected here.
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