Logical reasoning PrepTest 111 · Section 4 · Question 20

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Phenomenon - A mastodon skeleton with a human-made projectile in it was found
Background
- (1) The mastodon went extinct during the Ice Age
(2) The projectile was different from those found in the parts of Eurasia closest to North America at the time
(3) Eurasians didn't settle in North America until right before the Ice Age
Explanation - The first settlers of North America from Eurasia came from farther away

Answer Anticipation:
This argument falls into a common pattern of reasoning we see on the LSAT—a phenomenon is raised, and an explanation for what happened is presented. However, that pattern, and the details, are buried under a whole bunch of information about the Ice Age at the time that we need to work through.

Let's start with the explanation/conclusion—the first Eurasian settlers in North America probably came from a part of Eurasia that wasn't closest to North America. Why does the author believe that?

It revolves around the phenomenon and the timeline. A mastodon was found with a human-made projectile, and it's known that mastodons went extinct around the peak of the Ice Age. On the same timeline, Eurasians didn't settle North America until right before the Ice Age—meaning there was a small window between the Eurasian settlement of North America and when this mastodon could have been hunted.

The projectile didn't resemble anything that was used by humans in the parts of Eurasia that were closest to North America, which the author takes to mean guarantees the projectile wasn't made by that group. That's not necessarily true, however, as they could have adapted their projectiles to local needs, so this is one potential avenue to weaken the argument.

However, assuming that the projectile's dissimilarity to anything used by that group of Eurasians does establish that this group wasn't the one that made the projectile, does that prove it was a group of Eurasians from farther away? Not at all—as with many phenomenon/explanation passages, this answer ignores the possibility that a non-Eurasian group made the projectile. Maybe it was Native Americans, or South Americans who migrated north during the Ice Age. This is another potential avenue for weakening the argument.

Answer Explanation:
This answer suggests that the projectile in question wasn't from Eurasian settlers at all, since it doesn't resemble anything they would have used, which lines up with the second assumption we noted. If the projectile was actually from a non-Eurasian group, then there's no evidence about Eurasian settlers at all in the stimulus, and so a conclusion that one group of them settled North America before another has no support. This weakens the argument by making the evidence cited in support of it irrelevant to it.

Key Takeaway:
This is a hard question, but the argument falls into a common pattern of phenomenon/explanation. When that happens, the argument is generally overlooking alternative explanations. Here, it assumed that the settlers were Eurasian, neglecting the possibility that they were from North or South America, or somewhere else.

Also, in a Weaken question, an answer that establishes the evidence isn't relevant to the conclusion weakens that argument. That can seem weird, as it doesn't provide evidence against the conclusion. However, a conclusion that goes from having some support—even if it's not great support—to having no support is weakened.

Incorrect. This answer is trying to get you to think that it provides evidence that the settlers in North America who hunted the mastodon were from the closer part of Eurasia because that group remained nomadic. However, them being nomadic in no way supports the conclusion that they were in North America at the time. They could have been nomadic but moved exclusively within Eurasia. At best, this answer establishes that it was possible that this group moved to North America, for reasons completely unrelated to the mastodon/projectile evidence, which wouldn't weaken the argument that another possibility is probable.

Incorrect. More and similar evidence to what is presented in an argument serves to strengthen arguments, not weaken them.

Incorrect. This answer provides more evidence that it was the Eurasians from farther away that settled North America during this time, thus strengthening the argument.

Incorrect. First, this answer is about the time period just before the Ice Age, whereas the stimulus talks about Eurasians settling in North America shortly before the peak of the Ice Age. Second, humans in Eurasia would have no way of knowing that the conditions in North America were better—that's far away, and they didn't have the internet and Weather.com! Third, this answer is relative—North America could have been marginally more habitable at the time, and Eurasia could still have been very habitable to humans, thus not providing a reason to leave.