PrepTest 102, Section 3, Question 9
Ornithologist: The curvature of the claws of modern(68 more words not shown)
Which one of the following(9 more words not shown)
- AModern tree-dwelling birds(6 more words not shown)
- BArcheopteryx made use(6 more words not shown)
- CThere have never(6 more words not shown)
- DArcheopteryx was in(5 more words not shown)
- EThe curvature of(14 more words not shown)
Reading the argument
What do the curved claws actually tell us about how Archeopteryx lived?
Perhaps they helped it grip branches. But they might also have been useful for grabbing prey. Even accepting that the claws enabled perching doesn't establish that the creature lived in trees. The paleontologist's chickens make that second point concrete: they perch in trees while remaining primarily ground-dwelling. We have to distinguish having a useful feature, using it in a particular way, and making that use central to a way of life.
What we’re looking for
This time the question asks what the ornithologist's argument depends on. I want a connection between the claws and the behavior we're trying to infer from them. If the claws' curvature tells us nothing about what the creature actually did, why use it as evidence of where it lived? Look for something the ornithologist needs for this line of reasoning.
Working the answers
- A
Similar structures can be compared without the modern birds being direct descendants of Archeopteryx. The argument relies on the similarity in claw shape and proposed function, not a stated family tree. Direct descent isn't required for that comparison to be informative.
- BCorrect
Archeopteryx must have made use of the claws' curvature for the ornithologist's proposed connection to work. If the curvature played no part in its activities, the fact that it could have helped with perching wouldn't establish the suggested tree-dwelling behavior.
This is a modest requirement, not proof of the whole conclusion. Using the curved claws to grab prey would satisfy B without making the creature tree-dwelling. That's consistent with our earlier objection. An assumption the argument needs can be necessary for its reasoning while still falling short of making every step convincing.
- C
The ornithologist doesn't need curved claws to be the only possible way a bird can live in trees. Another bird might grip branches through some different feature. That wouldn't prevent these curved claws from being useful evidence about Archeopteryx. A proposed way of doing something doesn't have to be the only way.
- D
Earliest known and actually earliest aren't the same. An earlier birdlike creature might be discovered later. More importantly, the argument about habitat relies on claw shape, not on Archeopteryx winning a contest to be first. Its place in that chronology needn't settle whether it lived in trees.
- E
The ornithologist cites this evidence without saying it is the only evidence available. Other evidence could also support a tree-dwelling life. That would not undermine using the claws as one piece of support. The argument needs this feature to matter; it doesn't need every other potential source of evidence to be absent.
More Necessary Assumption questions
Learn the LSAT our way
Our platform drills Necessary Assumption questions at your level and adjusts as you improve.