#16 - A favored theory to explain the extinction of

[Administrator]

Complete Question Explanation

Weaken. The correct answer choice is (E)

This question asks you to weaken the asteroid impact theory, so you should look to critique the idea that an asteroid impact caused the extinctions.

Answer choice (A): The fact that some dinosaurs congregated closely does not have clear relevance to whether an asteroid strike would have caused the extinction, so this choice is wrong.

Answer choice (B): You should not assume that a theory about complete global extinction would be affected by the fact that some dinosaurs migrated and could escape local catastrophes, because the asteroid strike is presented, word-for-word, as “globally catastrophic.” Furthermore, it is fundamentally incorrect to presume that simply because an asteroid strike must occur locally, the catastrophic effects must be local. This choice does not address the large asteroid strike in question, and is incorrect.

Answer choice (C): The fact that people were familiar with the fossils of dinosaurs establishes little about the time at which dinosaurs went extinct. This choice should be eliminated immediately. If you read it incorrectly, you may have believed that this choice inferred that people lived at the same time as dinosaurs. It does not; furthermore, the possibility that humans survived an asteroid strike is not good evidence that the strike did not cause the extinction of dinosaurs, since the species are very different.

Answer choice (D): The fact that large dinosaurs lived in an environment in which only small animals can live today might be taken to support the idea that dinosaurs were tough creatures that were better able than are today’s animals to handle dry environments. However, this incorrect choice merely implies that dinosaurs might be better than are today’s creatures at surviving a single presumed effect of an asteroid strike, which is definitely not good evidence that dinosaurs were overall better equipped to, or at all able to, survive all the actual effects of an asteroid strike.

Answer choice (E): This is the correct answer choice. If the numbers of dinosaur species are drastically decreasing both below (before) and above (after) the layer of extraterrestrial dust, that suggests that the extinctions probably occur before and after the asteroid strike, and thus that there is another important cause of the extinctions. That indicates that the asteroid-impact theory is probably not a complete explanation.

[PositiveThinker]

So is E essentially saying that "we see a decrease in the amount of dinosaurs that existed after the asteroid hit, but the dinosaurs do still exist"

Which basically weakens the argument that the asteroid did cause the *extinction*??


I ask questions regarding the diction and vernacular of a lot of these abstract answer choices and stimuli. I do that so i have a better idea of what these things are saying and have a better chance on my own to parse out the grammar during practice and when the real test comes. Obviously the LSAT makers are not my friends so i don't expect them to make these things any easier. But understanding the ideas has been so beneficial to me moving forward. That is why i ask.

[Emily Haney-Caron]

Hi PositiveThinker,

Great question! E is essentially saying that the majority of species went extinct before the asteroid hit (and we know because the number os species whose fossils were found at different layers dropped from 35 to 13 all below the dust that marks the point where the asteroid fell). Does that make sense?

[PositiveThinker]

Hi PositiveThinker,

Great question! E is essentially saying that the majority of species went extinct before the asteroid hit (and we know because the number os species whose fossils were found at different layers dropped from 35 to 13 all below the dust that marks the point where the asteroid fell). Does that make sense?

yes this makes sense. Which means that i didn't understand fully what E was saying. Even though i eliminated all the wrong answer choices correctly, i couldn't parse out what E was actually saying. Im glad. thanks a lot!

[LSAT2020]

Answer choice E is still giving me a hard time. I had to draw it out to try to better understand:

35 fossils found , 13 teeth found
_____________________________________ (above the line is extraterrestrial dust, and below there is none)

13 fossils found, 5 teeth found



I'm not sure if I interpreted E correctly. If so, does it matter that the numbers at the top are higher than those at the bottom? If the numbers were lower at the top and higher at the bottom, couldn't you still conclude that it may not have been the asteroid that caused the extinction of the dinosaurs, since dinosaurs were still dying before the extraterrestrial dust?

Thanks in advance!

[Luke Haqq]

Hi LSAT2020!

I'd be happy to address answer choice (E) more in depth.

First, let's briefly summarize what is covered in the stimulus. It explains that one theory--the "asteroid-impact theory"--makes a particular cause-and-effect claim. Under asteroid-impact theory, an asteroid impact was the cause and the effect was dinosaur extinction:

C E
asteroid extinction (asteroid-impact theory)

Under a "new competing theory," it was not an asteroid impact that caused the extinction of dinosaurs. The stimulus notably does not claim that this new theory claims that such an asteroid impact never happened. Rather, the new theory claims this is not what caused the extinction of dinosaurs because the cause was instead volcanic eruptions:

C E
eruptions extinction (new theory)

With these diagrams of the information from the stimulus in hand, we can next turn to the question stem. The question asks us to select the answer choice that, if true, "most strongly indicates that the asteroid-impact theory is at least incomplete, if not false"--it thus asks for us to weaken the cause-and-effect reasoning behind asteroid-impact theory.

Finally, turning to answer choice (E), that answer states, "The fossil record in Montana from below the layer of extraterrestrial dust shows a diminution over time in dinosaur species from 35 to 13, and dinosaur teeth found above the dust layer show a diminution in species from 13 to 5." What this answer choice does is it suggests that the "layer of extraterrestrial dust" (which would be evidence of an extraterrestrial cause like an asteroid) doesn't have much of a bearing on dinosaur extinction. If one looks below that layer, one will see a diminution of dinosaur species to roughly a third of the prior level. However, if one looks above the layer, one will see the same thing--a diminution roughly to a third of the prior level of species. Further, since there was a considerable decrease in dinosaur species before the asteroid impact even happened (the decrease from 35 to 13 below the layer of extraterrestrial dust), this suggests an alternative cause. This alternative cause might be volcanic eruptions, as suggested by the new, competing theory, or it might be some other cause, but it is unnecessary to go that far. Rather, (E) is the correct answer choice because it weakens asteroid-impact theory by pointing to some alternate cause, based on the lack of much difference in the diminution of dinosaur species before and after the asteroid impact.