LSAT 123 – Section 3 – Question 25

LSAT 123 - Section 3 - Question 25

June 2007

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Target time: 1:25

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Question QuickView	Type	Tags	Answer Choices	Curve	Question Difficulty	Psg/Game/S Difficulty	Explanation
PT123 S3 Q25	+LR	Flaw or descriptive weakening +Flaw Conditional Reasoning +CondR	A 27% 158 B 8% 147 C 23% 148 D 27% 150 E 14% 150	154 161 168	+Hardest	144.044 +SubsectionEasier

J.Y.’s explanation

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Some anthropologists argue that the human species could not have survived prehistoric times if the species had not evolved the ability to cope with diverse natural environments. However, there is considerable evidence that Australopithecus afarensis, a prehistoric species related to early humans, also thrived in a diverse array of environments, but became extinct. Hence, the anthropologists’ claim is false.

Summarize Argument: Counter-Position

The author concludes that the claim “ability to cope in diverse natural environments was necessary for humans to survive prehistoric times” is false. This is based on evidence that a species related to early humans had the ability to cope in diverse natural environments, but didn’t survive.

Identify and Describe Flaw

The author confuses the claim that coping in diverse environments was NECESSARY for human survival with the claim that coping in diverse environments was SUFFICIENT for human survival. This confusion is why the author thinks his evidence is relevant. The fact a related species had the ability to cope in diverse environments but didn’t survive doesn’t show that the ability wasn’t necessary. It shows that the ability wasn’t sufficient; but the claim the author calls false didn’t say that the ability was sufficient.

confuses a condition’s being required for a given result to occur in one case with the condition’s being sufficient for such a result to occur in a similar case

The anthropologists claimed that coping ability was required for humans’ survival. But the author misinterpreted that as a claim that coping ability was enough to survive in a similar case (species related to humans). This is why the attempt to reject the initial claim is flawed.

takes for granted that if one species had a characteristic that happened to enable it to survive certain conditions, at least one related extinct species must have had the same characteristic

The author uses the fact the extinct species had the coping ability as a premise. So the author isn’t assuming that the extinct species had this quality simply because humans had it. There’s evidence that the extinct species had it, and we should just accept this as true.

generalizes, from the fact that one species with a certain characteristic survived certain conditions, that all related species with the same characteristic must have survived exactly the same conditions

The conclusion is not drawn “from” the fact one species survived. It’s drawn from the fact a related species went extinct. Also, the author doesn’t conclude that “all related species” with coping ability survived the same conditions.

fails to consider the possibility that Australopithecus afarensis had one or more characteristics that lessened its chances of surviving prehistoric times

(D) goes along with the author’s misinterpretation. If the related species had features that made it less likely to survive, that’s a reason to think coping in diverse environments doesn’t ensure survival. But that’s the author’s point — coping ability doesn’t ensure survival.

fails to consider the possibility that, even if a condition caused a result to occur in one case, it was not necessary to cause the result to occur in a similar case

There’s no condition that caused a result. The related species in the premise had coping ability, but died; this doesn’t mean coping caused extinction. With respect to humans, the anthro.’s claim is that coping was required for suvival. This doesn’t assert coping caused survival.

Relevant lessons: Conditional logic | Contrapositive mistakes | How to approach Flaw/Descriptive weakening questions | 21 common flaws

LSAT 123 – Section 3 – Question 25

LSAT 123 - Section 3 - Question 25

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J.Y.’s explanation

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LSAT PrepTest 123 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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