## #19 - Paleontologist: It is widely, but falsely, held that

angie23

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I was stuck between C and D and unfortunately picked C because I thought that the answer choice does not have any impact on the argument. Can someone show me how C) strengthens? Thanks!
Lucas Moreau
PowerScore Staff

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Hello, angie,

Answer choice C strengthens because since carbon 14 was found "throughout" these 1.2 billion year old rocks, and parts of them were clearly never submerged in water, that means that water-dwelling life could not have imbued the dry parts of the rocks with carbon 14. This strengthens the conclusion that there was in fact life on dry land more than half a billion years ago.

Hope that helps,
Lucas Moreau
brettb
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I'm having trouble understanding how answer choice D doesn't strengthen the argument.

If plants & microbes extract C14 from the atmosphere to fuel reactions then release C14 when they die. Is it unreasonable to think that it's released back into the atmosphere? This to me doesn't seem like a far reaching assumption or an one that is by common sense standards implausible. And it seems like the argument implies that it is in fact released back into the atmosphere.

D says the rocks were formed from soil that contained very small amounts of C14 that entered directly from the atmosphere. But if we know that C14 is released to atmosphere by plants and microbes when they die then the fact that it is a very small or large amount of C14 shouldn't actually matter. Because either way it came from a living microbe/plant.

The way I'm looking at this from a diagrammed point of view is

A = Microbes/Plants release C14 to atmosphere when they die
C = C14 enters rocks

B is new information in answer choice
B = enters soil from atmosphere & forms rocks

B simply adds an extra step in the process to make the chain go from A > C
to
A > B > C

I guess a lot of this hinges on the assumption I made that it is released back into the atmosphere. Can someone tell me why this assumption is or isn't incorrect? Or any other problems I'm running into with my logic.

Thanks
David Boyle
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brettb wrote:I'm having trouble understanding how answer choice D doesn't strengthen the argument.

If plants & microbes extract C14 from the atmosphere to fuel reactions then release C14 when they die. Is it unreasonable to think that it's released back into the atmosphere? This to me doesn't seem like a far reaching assumption or an one that is by common sense standards implausible. And it seems like the argument implies that it is in fact released back into the atmosphere.

D says the rocks were formed from soil that contained very small amounts of C14 that entered directly from the atmosphere. But if we know that C14 is released to atmosphere by plants and microbes when they die then the fact that it is a very small or large amount of C14 shouldn't actually matter. Because either way it came from a living microbe/plant.

The way I'm looking at this from a diagrammed point of view is

A = Microbes/Plants release C14 to atmosphere when they die
C = C14 enters rocks

B is new information in answer choice
B = enters soil from atmosphere & forms rocks

B simply adds an extra step in the process to make the chain go from A > C
to
A > B > C

I guess a lot of this hinges on the assumption I made that it is released back into the atmosphere. Can someone tell me why this assumption is or isn't incorrect? Or any other problems I'm running into with my logic.

Thanks

Hello brettb,

Though carbon 14 may be released by microbes, that doesn't it must be. So if an alternate source of the carbon 14 in the rocks is the atmosphere rather than microbes, that's the way it is.
Whether the microbes/plants release back into the atmosphere or not (and they may well do so), that isn't the real issue here.

Hope this helps,
David
Khodi7531
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Im so confused on this question. I chose C and I didn't realize the importance of " though other portions clearly never were" - probably just glanced over it so I see why C wouldn't work.

But D....I have no idea how this can work. I see how it says the rocks were actually formed from soil and the soil, as a result of the atmosphere, brought in small amounts of C14. The ONLY way I can justify D is because the stimulus says the C14 came from plants and microbes but D says it came from the atmosphere..... is that why D is correct, and the only one of the 5 that is "strengthen EXCEPT"?

If so...it's veryyyy strange to me for answers to be like this. Because overall, the conclusion still stands for the most part. Me hearing that it came from the atmosphere and not plants and microbes doesn't really feel like it hurts the idea of the Paleontologist - that life existed longer than half a billion years.

But then again because it's going for the direct evidence that the Paleontologist used to reach is conclusion...I guess that's why this is the answer?

What's the approach here, am I in the ball park? Any recommended way for me to approach this in the future a different way? Anytime after review from #17+ I get a TON wrong and don't blame myself because even without time i'll sit and look at the question for 10 minutes thinking like, how could I have seen this when I have 30 seconds?
Robert Carroll
PowerScore Staff

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Points: 436

Khodi,

This is a Strengthen - Except question. The four wrong answer choices will strengthen the argument, and the correct answer choice will not strengthen it. You seem to think that the correct answer choice will weaken the argument. It doesn't have to. The logical opposite of "strengthen" is "does not strengthen," so anything which doesn't affect the argument at all would fail to strengthen it and thus be correct (because of the "except" nature of this question).

However...it seems to me that answer choice (D) does weaken the argument. If the carbon-14 came from the atmosphere directly, then the rocks did not get their carbon-14 from life. Because these rocks were the only evidence the paleontologist had, if they don't provide proof of life 1.2 billion years ago, the paleontologist has no evidence.

The issue here is understanding how the argument works and what evidence it has. The carbon-14 in the rocks has to have come from life forms, and, more than that, life forms on land, for the paleontologist's argument to work.

If you're getting things wrong after #17, realize some of these questions are more difficult, and it can be helpful to concentrate on earlier questions to try to get as many of those correct as possible. Then allocate your time later in the section so that you're getting at least some questions correct. Rushing to try to finish all the questions without putting enough thought into the questions to make sure of getting them right won't work. If you finish only 20 questions, but get all of them right, you're putting yourself in a great position. Getting to every question but getting only 15 right because you rushed too much to make sure of your answers is worse.

Robert Carroll