Explanations for PT 59 (Dec 2009) Section 2 LR PLZ?

ola_em
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Explanations for PT 59 (Dec 2009) Section 2 LR PLZ?

Postby ola_em » Wed Sep 15, 2010 1:56 pm

#5, 7,15, 21,26

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Re: Explanations for PT 59 (Dec 2009) Section 2 LR PLZ?

Postby Atlas LSAT Teacher » Wed Sep 15, 2010 5:38 pm

#21 -

This is a weakener question, so find the core. The conclusion is that the disease-causing bugs brought by prehistoric migrants to North America were probably the main reason that many animals encountered by these folks became extinct 2,000 years later. Why? Because it is implausible that hunting by these migrants could have had this effect and the migrants surely had some disease-causing bugs with them. We have an argument involving causation, so we would expect the gap has something to do with some other path of causation. Couldn't it have been something else that resulted in the extinctions? Just because you've ruled out one reason doesn't mean it has to be another one.

It turns out that this is a rare weakener where we find a premise attacked instead of the connection between the premises and the conclusion. (C) calls into question the statement that the hunting could not have had this effect by noting that the animals that were not hunted tended to not go extinct as quickly (or at all perhaps). Analogously, let's imagine that someone argues that even though most New Yorkers have a cough, living in NY does not cause you to cough. If you can show that a very small percentage of those who live outside of NY cough, you've called that argument into question. You're strengthening the connection between coughing and living in NY (though still not proving a specific causation). Similarly, the essayist shows that there is a strong correlation between hunting and extinction.

The wrong answers are tricky.

(A) does not weaken the conclusion but instead explains how disease would have led to extinctions.

(B) is out of scope - we are not interested in how the disease-causing bugs affect humans.

(D) is tempting. While the part about some humans being immune to the diseases is irrelevant, perhaps the part about some animals being immune weakens the idea of these bugs destroying the animals. However, we don't know that many animals would have been unaffected, nor do we know which species -- does this even apply to the prehistoric animals we're discussing?

(E) is too weak to weaken! Of course some species became extinct later - what does that have to do with why the ones that did go extinct actually did? Frankly, it'd be pretty crazy if all the extinctions happened within those first 2,000 years. What would the nature channel make us feel bad about?

Some of the other questions are explained are here: http://www.atlaslsat.com/forums/preptes ... -f139.html

[edited for clarity]




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