LSAT 155 - Section 1 - Question 05

This is a Strengthen question.

We’re asked to find support for the paleontologist's hypothesis, which is the conclusion of the argument.

Here we have an argument that presents phenomena followed by a hypothesis that tries to explain the phenomena. We start with the set of dinosaurs, then we move into the subset called ornithomimids, which are birdlike, then we move into a further subset called the later-ornithomimids, which had toothless beaks and weak jaw muscles. A fossil of one particular member of that subset called G. bullatus shows a comblike plate inside its beak. We know that in modern birds like ducks and geese, plates like that are used to strain small bits of food from water and mud. So the argument concludes with a hypothesis that G. bullatus also fed by filtering food from water and mud.

The phenomenon is that G. bullatus has a comblike plate, and the hypothesis explains the function of the beak: for feeding. Support also comes from a premise about modern ducks and geese. That means this argument also uses reasoning by analogy. Therefore, one assumption is that the functionality of the beaks on ducks and geese is relevant as evidence of their function on G. bullatus .

As with most Strengthen and Weaken questions where the stimulus takes the form of phenomena-hypothesis, it's hard to anticipate the right answer choice because there are so many different directions that the question can go. Usually, the best strategy is POE.

Answer Choice (A) says some dinosaurs with toothless beaks and weak jaw muscles are believed to have pursued small prey and to have eaten eggs. First, it’s not clear how this is relevant to G. bullatus. If we assume that the dinosaurs in this answer exhibit similar behavior to G. bullatus, then that's not good for the hypothesis. This reveals that dinosaurs with toothless beaks can feed in some other manner. But this is not an effective Weaken answer choice either precisely because we have no reason to assume that the dinosaurs in this answer exhibit similar behavior to G. bullatus.

Answer Choice (B) says toothless beaks and weak jaw muscles were not common to any dinosaur group other than ornithomimids. All this tells us is that toothless beaks and weak jaw muscles are good evidence that the creature belonged to ornithomimids. If we were trying to identify a particular fossil and it showed signs of toothless beaks and weak jaw muscles, then this information might be helpful. However, the phenomenon we’re trying to explain above is what functionality comblike plates had. (B) doesn't help resolve that issue.

Answer Choice (C) says that except for the comblike plates in their beaks, G. bullatus shared few anatomical features with modern ducks and geese. (C) stresses points of dissimilarity between G. bullatus and modern ducks and geese. Whatever it's doing, it's certainly not strengthening the analogous reasoning above. But it's also not weakening that reasoning either, at least not by much, because (C) doesn't tell us what the few anatomical features that are shared between the two are. It merely tells us that there are few that are shared while most are not shared. But what we really need to know in order to either weaken or strengthen the reasoning by analogy is not just the proportion of similar to dissimilar features, but rather exactly which features are similar or dissimilar, because only the relevant similarities and dissimilarities matter, not all of them.

Correct Answer Choice (D) says most G. bullatus fossils have been found in sediments deposited in lakes, rivers, and other wet environments. This is evidence that corroborates the hypothesis by empirically confirming a prediction. If it's true that G. bullatus fed by filtering food from water and mud, then one would predict that these animals lived near water and mud. And if that's true, then one would expect to find their fossils near wet environments.

This is not dispositive evidence that the hypothesis is true. It is just another piece of evidence that gives a bit more weight to the hypothesis. In other words, it strengthens. You can see this by changing the quantifier on this answer choice. If instead of “most,” it said “nearly half,” or “some,” then the weight of this evidence diminishes accordingly. In fact, if it said “none,” then this would disconfirm a prediction of the hypothesis, which would weaken the hypothesis. Now, you might have concerns in the back of your mind like, “Wait, we’re talking about fossils, and surely after tens of millions of years, the fossils moved around.” Those are legitimate concerns. But I think the answer choice largely takes care of that by telling us that the fossils were found in sediments deposited near wet environments.

Answer Choice (E) says paleontologists have not found evidence that any dinosaur other than G. bullatus had comblike plates. This is similar to (B). If the issue above was that of identification, like if we had to figure out what species a particular fossil belonged to, then (E) may be relevant. If G. bullatus is unique in having comblike plates, then finding a fossil with comblike plates is evidence that the fossil is one of G. bullatus. But this is not the issue in the argument above. Rather, the issue is about the functionality of the comblike plates.