LSAT 158 | Section 3 | Logical Reasoning: Q20

LR Question 20 Explanation

QUESTION TEXT: The study of primates is interesting for many reasons…

QUESTION TYPE: Must be True

FACTS:

1. Only primates have opposable thumbs.
2. Lemurs are lower primates.
3. The only primate indigenous to Madagascar is the lemur.
4. Some lemurs are the only living diurnal primates.
5. All higher primates are thought to have evolved from a single diurnal lower primate.

ANALYSIS: This question gives us a lot to work with. It would be impossible to try to prephrase something here, as there are a lot of possibilities. It’s best in this case to start assessing answers.

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1. This is not supported by the stimulus. You may have picked this one because it seems to be properly inferred from facts 4 and 5. However, what you’re missing is that lemurs are the only living diurnal primate. It’s possible that chimpanzees evolved from a species that is now extinct.
2. CORRECT. We know from fact 3 that the lemur is the only primate indigenous to Madagascar. We also know that lemurs are lower primates. Therefore, there are no higher primates indigenous to Madagascar.
3. All higher primates evolved from a diurnal lower primate, but they could have adapted to become nocturnal.
4. We don’t know really anything about whether lemurs have opposable thumbs. We know that opposable thumbs are only found in primates. But it could be that all lemurs have opposable thumbs, or no lemurs have opposable thumbs.
5. It’s possible, but we can’t say for sure. We know that some lemurs are the only living diurnal primates. But remember – on the LSAT, ‘some’ can mean anywhere from ‘one’ to ‘all’. If one lemur species is diurnal, other species could be nocturnal.

Recap: The question begins with “The study of primates is interesting for many reasons”. It is a Must be True question. Learn more about LSAT MBT questions in our guide to LSAT Logical Reasoning question types.