LSAT Explanation PT 41, S3, Q22: Paleontologists recently discovered teeth from several

LSAT Question Stem

Which one of the following, if assumed, would allow the conclusion to be properly drawn? 

Logical Reasoning Question Type

This is a Sufficient Assumption question. 

Correct Answer

The correct answer to this question is D. 

LSAT Question Complete Explanation

Let's first break down and analyze the argument in the passage. The passage states that paleontologists found teeth from several woolly mammoths on an isolated Arctic island where no mammoth fossils had previously been found. These teeth were 25 percent smaller on average than adult mammoth teeth found elsewhere. The conclusion drawn is that, provided the teeth are representative of their respective populations, woolly mammoths that lived on the island were smaller on average than those that lived elsewhere.

In this argument, the premise is that the teeth found on the island were 25 percent smaller on average than adult mammoth teeth found elsewhere. The conclusion is that woolly mammoths on the island were smaller on average than those that lived elsewhere.

To make this more understandable, let's use a simple example. Imagine we found shoes on two different islands. On one island, the average shoe size is 25 percent smaller than the shoe size found on the other island. If we assume that shoe size is representative of the people's height, we might conclude that people on the first island are shorter on average than those on the second island.

An "Evaluate" question for this argument would be: "Is the size of the teeth proportional to the overall size of the mammoths?"

Now, let's discuss the answer choices:

a) This answer choice states that neither tooth size nor overall body size is completely uniform among adult members of most species, including woolly mammoths. This does not help us prove the conclusion that island mammoths were smaller on average based on their smaller teeth.

b) This answer choice discusses the tooth wear that naturally occurs in many animals over the course of their adult years. It states that this wear did not result in a significant change in tooth size among adult woolly mammoths as they aged. While this information is interesting, it does not connect mammoth size to tooth size, so it cannot prove the conclusion.

c) This answer choice talks about unusually small mammoth teeth found at locations other than the island. It states that these teeth have always been those of juvenile mammoths rather than adult mammoths. However, this information is irrelevant to the conclusion, which is about mammoths found on the island.

d) This answer choice states that tooth size among adult woolly mammoths was always directly proportional to the overall size of those mammoths. This is the correct answer choice because it links tooth size with actual mammoth size, showing that the two are related and that teeth are indicative of overall size. If mammoth size is always proportional to tooth size, then mammoths with smaller teeth would be smaller than mammoths with larger teeth, and the conclusion would be true.

e) This answer choice states that woolly mammoths of the kind that lived on the island had the same number and variety of teeth as mammoths that lived elsewhere. While this information might be interesting, it does not help us prove the conclusion that island mammoths were smaller on average based on their smaller teeth.