Q14 - Geologists recently discovered marks

[boasfin]

hello,

Why D? What's wrong with C? More importantly, I see the logical leap between marks made a 1/2 a billion years earlier and marks probably the traces of geological processes rather than worms. However, I def don't see how D addresses it. thank you!

[ManhattanPrepLSAT1]

Thanks for posting your question on the forum! Answer choice (D) addresses both the time when the marks were made (half a billion years before multi-cellular life) and the geological processes the argument concludes were responsible for leaving the marks. According to this answer choice, the geological processes could not have occurred at the time the marks were left. This puts a big question mark on whether the marks were left by geological processes.

We can eliminate the other answer choices for the following reasons:

(A) attempts to call into question the evidence. However, this answer choice is consistent with the evidence that this particular field of sandstone is half a billion years older than the first multi-cellular life. Regardless, we need to call into question the conclusion, and almost never is attacking a premise the correct approach.
(B) supports the conclusion.
(C) doesn't push the date back far enough. Even if there were these other life forms, they too would only exist way after the marks were left on the sandstone.
(E) is irrelevant. Those worms wouldn't exist until a half of billion years after the marks were left on the sandstone.

Hope that answers your question!

[goriano]

Thanks for posting your question on the forum! Answer choice (D) addresses both the time when the marks were made (half a billion years before multi-cellular life) and the geological processes the argument concludes were responsible for leaving the marks. According to this answer choice, the geological processes could not have occurred at the time the marks were left. This puts a big question mark on whether the marks were left by geological processes.

We can eliminate the other answer choices for the following reasons:

(A) attempts to call into question the evidence. However, this answer choice is consistent with the evidence that this particular field of sandstone is half a billion years older than the first multi-cellular life. Regardless, we need to call into question the conclusion, and almost never is attacking a premise the correct approach.
(B) supports the conclusion.
(C) doesn't push the date back far enough. Even if there were these other life forms, they too would only exist way after the marks were left on the sandstone.
(E) is irrelevant. Those worms wouldn't exist until a half of billion years after the marks were left on the sandstone.

Hope that answers your question!

While I agree that (D) is the correct answer, I don't think (E) is as irrelevant as you suggest (please correct if I am wrong)

The stimulus states that the the marks were made more than half a billion years earlier than the earliest KNOWN traces of multicellular animal life. I saw (E) as capitalizing on this uncertainty, saying that evidence of their earliest existence is scarce.

Could (E) have been eliminated because it just elaborates on what has already been presented in the stimulus?

[ManhattanPrepLSAT1]

While I agree that (D) is the correct answer, I don't think (E) is as irrelevant as you suggest (please correct if I am wrong)

You're right, irrelevant was probably too strong a word. Answer choice (E) does discuss worms as one of the earliest forms of multicellular existence. But the problem with answer choice (E) is that it does not push the period of when worms appeared on Earth forward at all. It says that the evidence of their existence is scarce, but does not provide any reason to believe that they existed before our earlier estimates of the arrival of multicellular life.

Make sense?

Could (E) have been eliminated because it just elaborates on what has already been presented in the stimulus?

When you say elaborate, do you mean that it is just restating a claim, or that it is adding something new. Adding something new is exactly what we're looking for from the correct answer, but simply restating a claim from the argument, would neither strengthen nor weaken an argument.

Hope that helps!

[melmoththewanderer88]

I'd like to join the discussion on (E).

To me it suggests that the "earliest known traces of multi-cellular life" may not be complete, because the evidence, being composed of soft tissue may not have been fossilized.

So do we now weigh (E) with (D)?

(E) presents the realm of possibility... it is possible that the worm evidence may not be complete

and (D) which presents the realm of likely impossibility (so, for that reason, it is stronger)... the most likely geological cause was impossible at the time of the sample.

This was my process to selecting D, but would like to know if this is a valid way of approaching this question.

[zainrizvi]

(D) seemed a bit off to me because it said that "At the place where the sandstone was FOUND".... but what if it was found somewhere else? Didn't seem to be strong enough for me. Am I holding weaken questions to too high standards? Weaken are not necessary assumptions after all...


(C) seemed tempting because the argument is assuming that only multi-cellular animals are leaving those tracks... what if some early life forms could have done that? Or is my interpretation a bit off because I'm assuming early life forms = single celled, whereas early life forms could mean anything... I can't just use the assumption that supports my case?


Confused a bit...because we are assuming in (D) that it was not misplaced (i.e. the place it was found was where the geological processes must have occurred), but we can't make the assumption and use the "favorable interpretation" of (C).... why is that?

[zip]

To determine why E is wrong consider what it actually says. Some have interpreted E as saying , or at least implying that the record regarding worms is incomplete. It doesn't. It says the evidence is sparse, which doesn't mean it is insufficient. The problem with E is that it just doesn't address the issue specifically regarding the reliability of the record of worms' first existence. Even if it were true then , it wouldn't weaken the argument. If it were stated that the record of the earliest worms is incomplete, that would be relevant and weaken the argument by undermining the force of the premise, but it doesn't say that, even though it's tempting to read into it and thus fall for the trap.

[timsportschuetz]

Regarding (C), I believe the most evident reason for eliminating this answer choice is due to the following reasons: The conclusion states that the marks on the stone are probably NOT from WORMS, but, rather from geological processes. (C) would, at best, tell us that "some other life form" caused these marks... This, however, would do absolutely NOTHING to the conclusion. The conclusion is more specific in this particular case (this is why this question is located in the first tough area of every LR section), since it specifically rules out WORMS. If the conclusion stated that the marks were caused by geological factors rather than ANY LIFE FORM, then (C) would be much more attractive! The author of the argument could simply respond to (C) by stating "OK, but I specifically am ruling out the worms to be the cause of the marks. Furthermore, I never stated that life other than those of multi-cellular forms could and/or couldn't have made these marks."

[allisonellen7]

I don't agree that undermining the idea that the marks were traces of geological processes doesn't undermine the conclusion. The conclusion specifically includes that idea. C undermines this idea by stating that other early life forms could have made the marks; just because MULTICELLULAR ANIMAL life has only been traced to as early as half a billion years later does not mean that some other early life form, which is known to make similar marks, did not exist at that time. Even E seems stronger to me than D. Worms are likely to have been among the earliest forms of multicellular animal life and evidence is scarce, so they could have existed before the earliest known traces; however, I do see the difference between incomplete and scarce evidence now, which is helpful. Finally and most importantly, D seems like a very weak answer because it says "AT THE PLACE WHERE THE SANDSTONE WAS FOUND." Is it not possible that in billions of years, this piece of sandstone could have moved????? I have seen this exact scenario in other questions be the reason to eliminate a wrong answer choice, so this is extremely frustrating to me!! Thank you to anyone who can help explain how one should find the right answer.

[Garychou007]

Regarding (C), I believe the most evident reason for eliminating this answer choice is due to the following reasons: The conclusion states that the marks on the stone are probably NOT from WORMS, but, rather from geological processes. (C) would, at best, tell us that "some other life form" caused these marks... This, however, would do absolutely NOTHING to the conclusion. The conclusion is more specific in this particular case (this is why this question is located in the first tough area of every LR section), since it specifically rules out WORMS. If the conclusion stated that the marks were caused by geological factors rather than ANY LIFE FORM, then (C) would be much more attractive! The author of the argument could simply respond to (C) by stating "OK, but I specifically am ruling out the worms to be the cause of the marks. Furthermore, I never stated that life other than those of multi-cellular forms could and/or couldn't have made these marks."

I think what went wrong with C is that to be a weakening AC, it requires too much inference. True, if we can recognize the possibility where the mark is done by other life form, we can, therefore, weaken the conclusion, which states that the mark is done by geological process. However, in order to recognize that possibility from C, which states that there were life forms that could make similar marks, we need to infer that the life form causing mark really apply to our situation. But we have no strong reason to believe this is the case. In fact, unless explicitly indicated, to make such inference is invalid. To make this a little bit clearer, if the C) states that the mark on the stone is likely to be made by other life form, the AC will be much more attractive.
Overall, C) is wrong because it is OS.

[allisonellen7]

That is very helpful! Thank you!

[513852276]

Alco, C is wrong because it didn't address the when and where those early life forms left marks. In answer choice, "...found in the piece of sandstone" is modified "those (recently discovered marks)" only. There is no implication at where the early life left marks. Maybe they left marks in another country. Also, when did early life left their marks? Maybe it's at a date after the earliest known traces of multicecullar animal life.

Just like we say an ancient spoon is found at Rome probably left by Julius Caesar rather than Emperor Nero, because it's left before Nero was born. "President Obama also has a similar spoon" is not weakening choice.

[contropositive]

I read the explanations provided for D and E. During review, I went for answer choice D but initially I had picked E because I assumed its putting a dent on the premise by implying that the knowledge of earliest known traces of multi. animal life is not complete. Reading the explanations, I understand how E is not actually explicitly telling us that.
However, wouldn't E also be wrong because it is unknown whether or not the author relies on "scientists knowledge" in his premise/evidence. When he discusses earliest known traces of mult. animal life he could have been relying on the knowledge of historians, who arguably could have a complete and accurate knowledge of earliest known traces of multi. animal life, so answer E doesn't really do much because it is unknown whether or not the author is relying on the knowledge of scientists.

That's my thought process for E. I am probably wrong.

[g1oriaaa]

After reading everyone's amazing response to this question I wanted to see if I can put it all together:

The first thing to do is identify the conclusion:
The marks are probably (more likely than not) the traces of geological processes rather than of worms.
Why is this?
Because the marks were made more than half a billion years earlier than the earliest known traces of multi-cellular animal life

The assumption that I see that is obvious is that the geologist is assuming that our knowledge of the earliest known traces of multi-cellular animal life is correct. The answer choice might have something to do with this or not. However this is not too important because the author does say "probably" in the conclusion so there is some wiggle room. Another obvious assumption is that if it not an animal then it is "non-living" creatures (i.e. geographical process) that was the cause of these traces. I think this is a warranted assumption since on a simple level we believe everything is liviing or nonliving. Sometimes pointing out an assumption can help us prephrase an answer in our minds before we look at the answer choices but this did not happen here really.

The LSAT creators tend to allow for us to weaken an argument's support of conclusion via premise regarding cause and effect in the following ways:
1. Find alternative cause for stated effect
2. show that even when cause occurs, effect does not occur
3. show that although the effect occurs the cause did not occur
4. show that the stated relationship is reverse
5. show that a statistical problem exists with the data used to make the causal statement. This most likely pans out by showing that the information is incomplete. Incomplete information for the lsat is defined as the author failing to consider all possibilities or relies upon evidence that still can be attacked by bringing up new possibilities because it does not have all the necessary or appropriate parts.

A. This does not weaken the argument. This tries to say that maybe it is the case that the sandstone is not as old as we think it is and therefore there may be a possibility that the age of the sandstone is young enough where there were worms but the operative/key word in this answer choice is "the PRECISE age" maybe we are off by a century, but in a grand scheme of things regarding billions of years, that still does not hurt the argument. Even if we do not know the precise year, we dont have to when talking billions of years. (I feel like there is a better way of explaining this but hopefully you get the gist). Furthermore there are a lot of assumptions that had to be made as you can see.
B. This strengthens the conclusion by saying yea cause happened (geological processes) and effect happened (left a substantial amount of marks) a bunch of times (the opposite of number two above) before early multi-cellular animals existed
C. Okay..but this answer choice does not do two things. It does not weaken the conclusion because it does not mention that it was not geographical process (totally omits that) and there is no time factor. (when were these early life forms?) there is a HUGE UNWARRANTED assumption that one has to make if you pick this to be your strengthening answer choice and that assumption is that the early life forms were around more than half a billion years earlier than stated in the argument. And even so, lets say that there were ants that also left these marks in some sand stones in general at some time in the past then why cannot it be geographical processes still for the specific sandstone in question?
E. This last one tries to be number 5 written above but fails miserably. SCARCE is not the same as INCOMPLETE. Maybe the scarce information we have has all the necessary parts we need to deduct what the argument in the stimulus says. This answer choice kind of coincides with answer choice A because once again yea it could be earlier but how much earlier? we would have to assume half a billion years earlier.

D is kinda simple and straight forward. It addresses the sandstone in question ("at the place where the standstone was found" so it starts off on a good note and then basically says that no stated cause (no geographical process) but still stated effect (still tracks in the sandstone) which is number 3 above.

Hope that some how helped. I wish I could be more technical in my writing but I too am still learning !

[WesleyC316]

C is wrong because we know nothing about those early life forms. If they were among the multicellular animal lives, then the answer choice could be immediately dismissed because we were already told by the stimulus that they couldn't have left the marks. If they weren't, then to make C right, we have to assume that they existed half a billion years before the earliest know multicellular animal life did, which is not a reasonable assumption.