LSAT 63, Logical Reasoning I, Q19, LSATHacks

LR Question 19 Explanation, by LSATHacks

QUESTION TEXT: Anthropologist: It was formerly believed that prehistoric…

QUESTION TYPE: Necessary Assumption

CONCLUSION: DNA testing shows that Neanderthals and humans did not interbreed.

REASONING: The DNA of contemporary (current) humans is very different from Neanderthal DNA.

ANALYSIS: This argument is assuming that human DNA has not changed significantly since the time the Neanderthals existed. It’s possible that early humans interbred with Neanderthals but we have lost those genes since that time.

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1. This would be a necessary assumption for anyone arguing that the two species interbred. But this argument is arguing that no breeding happened.
2. This would weaken the argument. The argument is stronger if DNA testing of remains is very reliable.
3. CORRECT. If the DNA of prehistoric homo sapiens was significantly more similar then perhaps the two species did interbreed. Then we could have lost that similarity over time and erased the evidence.
4. This would be helpful to the argument but it isn’t necessary. Species don’t breed merely because they are near one another.
5. This answer weakens the argument if true. The argument is concluding there was no interbreeding. This answer says that even the slightest similarity means there was interbreeding. Humans and Neanderthals probably have some similarity, even though are DNA is significantly different. 

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