June 2011 LSAT
Section 1
Question 19
Anthropologist: It was formerly believed that prehistoric Homo sapiens ancestors of contemporary humans interbred wi...
Reply
BenMingov on December 13, 2019
Hi Shafieiava, thanks for the question!This is actually a strengthen with necessary premise question. We can identify it as such because of the words "assumption" and "required". A strengthen with sufficient premise question stem will include a sufficient condition indicator, most commonly "if".
Let me provide two examples to make this clear:
Strengthen with necessary premise = Which one of the following is an assumption on which X's argument depends?
Strengthen with sufficient premise = Which one of the following, if assumed, allows the conclusion above to be properly drawn?
For strengthen with necessary premise questions, we will want to employ negation to ensure that we have selected the correct answer choice.
This argument takes the following form:
Based on a comparison between contemporary human DNA and Neanderthal DNA, the argument concludes that the former belief that ancient humans and Neanderthals mated can be disproved.
That's all nice and dandy, but it is making a brave assumption in that our DNA has not changed over time significantly. Perhaps Homo sapiens DNA was very similar to Neanderthal DNA due to mating many millennia ago.
This is answer choice C. Let's negate this answer choice to see what effect it would have on the argument.
Negated: The DNA of ancient humans "was" significantly more similar to the DNA of Neanderthals than that of contemporary humans.
This severely weakens the argument because this opens the door to our DNA changing over millennia and us losing the genetic trace of Neanderthal.
Answer choice E is incorrect because if any similarity in DNA is the result of interbreeding, then that means that ancient humans and Neanderthals more than likely did interbreed. The argument says our DNA is significantly different, but not entirely different. Additionally, you'd be surprised the small level of DNA similarity we have with other creatures in the animal kingdom. This would mean that any DNA similarity between us and rats, whales, etc. would be the result of interbreeding... I think you get the point!
I hope this helps. Please let me know if you have any other questions!