Q22 - Dinosaur expert: Some paleontologists

[hwsitgoing]

Hello,

I can see why D is correct, but what is wrong with C? If the expert assumes that the knowledge of fossils is complete and the oldest bird fossils are older than the dromeosaur fossils, wouldn't that imply that birds could no have evolved from dromeosaurs?

Thank you!

[maryadkins]

Good question!

Our core is:

earliest bird fossils date before the earliest dromeosaur fossils

-->

birds didn't descend from dromeosaurs

The assumption is that the dates of the fossils that have been discovered correspond to the dates when birds and Ds originated. (D) states it directly.

(A) doesn't work because the argument doesn't hinge on the characteristics point. That's the background information.
(B) is irrelevant. The issue is whether birds came from Ds.
(C) is tempting but doesn't get to the core issue--whether the dates of the fossils reflect the date of origin. If we know everything to know about the fossils, that still doesn't assure us that the fossils paint a complete picture of history. Maybe Ds preceded birds, but the earlier D remains that would have been "fossils" today were destroyed.
(E) is irrelevant.

[slimjimsquinn]

Could you explain further why the relative dates are necessary to the argument?

[chmeitzler]

I think this question hinges on the word known. "[Bird records] date back tens of millions of years before the oldest known dromeosaur fossils."

That is assuming that the record of known fossils accurately shows the dates of origin, which is what D says.

I think C is wrong because C discusses the knowledge of the fossils themselves. I think it would have to have the additional assumption that knowledge of the fossils = knowledge of the dates to get C to work.

[anjelica.grace]

Just to be clear ...

Is (C) wrong because having complete knowledge of the current fossil record does not preclude the possibility of there being older, undiscovered dromeosaur fossils not yet a part of the fossil record?

In other words, just because I know everything about the fossils in front of me doesn't mean that these are the only fossils ever. Am I right?

[sukim764]

Just to be clear ...

Is (C) wrong because having complete knowledge of the current fossil record does not preclude the possibility of there being older, undiscovered dromeosaur fossils not yet a part of the fossil record?

In other words, just because I know everything about the fossils in front of me doesn't mean that these are the only fossils ever. Am I right?

I like how you're able to analyze this answer choice in depth. However, you should try to always relate the answer choice into the argument core, especially if the question you're dealing with falls under the assumption family. As far as your analysis goes, I'm not sure I agree. The answer choice isn't wrong because it does 'not preclude the possibility of there being older, undiscovered dromeosaur fossils,' but rather it's wrong because it is just not necessary to conclude that birds did NOT descend from dromeosaurs. In other words, the fossil record can certainly contain one or a thousand more fossils that have yet to be discovered that may support or may not support the conclusion.

[yhyuna]

I was just wondering whether (d) can also be considered sufficient for the argument core. It seems to me it would be enough to make the argument work, but wanted to make sure. Thanks!

[noah]

I was just wondering whether (d) can also be considered sufficient for the argument core. It seems to me it would be enough to make the argument work, but wanted to make sure. Thanks!

I'm not seeing any reason it isn't. Good catch, we seem to have a necessary and sufficient assumption.

[redcobra21]

Hi

I saw this problem in the Manhattan LR strategy book, but I was still a little confused so I figured I'd give the forum a shot.

One thing that jumped out to me was the strength of the dinosaur expert's conclusion. The strategy book says that a negation of (C) does not "damage the conclusion at all," but I am having a hard time seeing why this is the case. The argument's conclusion is very definite (and somewhat extreme) insofar as the dinosaur expert rejects the paleontolgist's claim as false. But if (C) is negated and we now know that the fossile record is NOT complete, then how could the dinosaur expert still make such a strong conclusion that the paleontolgist's claim is false? He'd have to modify the conclusion by making it less definitive, which would destroy the original strength of the conclusion. As the strategy book states, there is the possibility that an older dromesaur fossil might be buried somewhere deep in the ground that we haven't discovered yet that came before the bird fossils, so the dinosaur expert would be forced to acknowledge that the absence of this evidence is not enough to prove the falsity of the claim. It seems like the negation would then "damage the conclusion"

Also, I'm not sure about (D) since it seems like this still depends on the fossil record being complete. It seems like LSAT common sense would allow us to assume that dating a fossil should tell us when that animal existed. So if you negate (D) and say that the known fossils do NOT indicate relative dates of origins, the dinosaur expert could say "that's fine, but that doesn't matter because the fossils still show that there were birds even when there were no dromeosaurs." To prove the dinosaur expert wrong, it seems like you'd have to make one additional move to show that there actually were other fossils showing an earlier date, which depends on the fossil record being complete.

Am I missing something? Would appreciate any help, and thanks!

[noah]

Great questions.

The second question is a bit easier to address than the first

Also, I'm not sure about (D) since it seems like this still depends on the fossil record being complete. It seems like LSAT common sense would allow us to assume that dating a fossil should tell us when that animal existed. So if you negate (D) and say that the known fossils do NOT indicate relative dates of origins, the dinosaur expert could say "that's fine, but that doesn't matter because the fossils still show that there were birds even when there were no dromeosaurs." To prove the dinosaur expert wrong, it seems like you'd have to make one additional move to show that there actually were other fossils showing an earlier date, which depends on the fossil record being complete.

The fossils showing the relative age is necessary. Even if there were some pieces of the puzzle (fossil record) missing, if the fossil record doesn't show the relative age of the animals, how can we use it all?

So, what it comes down to is whether "complete" is necessary for drawing conclusions from this record. But, this argument is all about whether the "some paleontologists" are justified in making their claim or not. Even if the fossil record is incomplete, the Dinosaur expert could use the bit of fossil evidence mentioned to argue that the paleontologist's appeal to the fossil record doesn't lead to their stated conclusion. As long as it shows relative age.

In other words, the record doesn't have to be complete, it just has to show the relative age.

I worry I'm just throwing the same words at you again. That help?

[agersh144]

I'm with everyone else, I think (C) is an additional necessary assumption. Think of it this way, the conclusion is that "paleontologists claim [the earliest bird fossils that have been discovered date back tens of millions of years father than the oldest known dromeosaur fossils and thus are descendants of a group of dinosaurs called dromeosaurs] is false."

How are they able to make such a definitive claim? Because they are by necessity assuming the KNOWN fossils record is in fact complete. If it were not complete they could assuredly make no such claim with certitude, only that given the available evidence such derivation is unlikely or improbable. What if we negate this necessary condition? The FOSSIL RECORD IS INCOMPLETE. Well if it's incomplete -- their opens a gaping hole in the argument -- the existence of undiscovered fossils that in fact indicate the opposite of what the paleontologists are claiming with certitude -- the existence of actual counterevidence that in fact the earliest fossils are indeed dromeosaur fossils and NOT bird fossils. This evidence would obliterate the argument and thus must be assumed in order for the definitive claim in the conclusion to be maintained. Thus (C) correctly identifies a necessary condition in addition to D.

Here's my motion to get this question removed from scoring lol

[noah]

Good discussion!

Here's an analogous argument that I think highlights why (C) is not necessary:

Gilad is convinced that Acme has committed tax fraud because the company only paid $1 in taxes last year. However, it turns out that when I reviewed Acme's tax return, Acme donated enough money to warrant a huge tax write-off. Thus, Gilad is wrong.

Do we have to assume that I saw each and every tax form? Is it OK if I didn't look at some tax form regarding a lost receive from an employee's trip to a conference? Yes, it's OK, as long as what I haven't seen doesn't screw up my argument. In essence, incomplete is OK as long as it's not misleading about the part I care about.

Anyone convinced now? Can I get a whoop-whoop?

[WaltGrace1983]

I understood (C) as only a sufficient assumption while (D) was necessary and (arguably) also sufficient. I agree with you, Noah!

[oscey12]

It's true that the way (C) has been described is a necessary assumption for the argument. It's the same reasoning that has proved dozens of assumption answers correct (negating answer choices to see if the argument still holds water), and I don't think that we're doing ourselves any favors by convincing ourselves otherwise. The only way that I could reconcile my problem with this question is that answer (C) says that our KNOWLEDGE of d-fossils and the earliest b-fossil is complete. This is not the same as our collection of the fossils being complete, only that of the fossils which we DO have, our understanding is complete (just because I have a complete knowledge about present-day relativistic physics doesn't mean that there can be no discoveries made in the future, and that the field is complete..choppy example but I think it works). Negating answer (C) doesn't open the door that introduces the possibility of older d-fossils than b-fossils (as would be a correct answer). The actual meaning of answer choice (C) is far weaker than others and myself had supposed.

[lsatzen]

I hated this question when I first saw it in the MLSAT LR book. But now upon review, I think I clearly see why (C) is not a necessary assumption.

Hopefully, my explanation is of some use to future MLSAT students.

Question Type: Necessary Assumption
1) Task: Pick an answer choice that must be true in order for the conclusion to be possibly true. With all Assumption Family questions, we should be on the look out for 1) the core 2) why the premises don't fully support the conclusion (i.e. identify the flaw(s) / gap(s) in logic)
2) Conclusion: Birds are not descendants of dromeosaurs.
3) Why? Premise: earliest discovered bird fossils are older than the earliest known dromeosaur fossils.
4) Identify the flaw(s)/gap(s):
Okay, we get a relative comparison between bird fossils and dromeosaur fossils. B-fossils are older than d-fossils. What does that tell us? Without imposing our own assumptions, it just tells us b-fossils are older than d-fossils, that's it. From this, the author concludes that birds are not descendants of dromeosaurs. But wait, how does he arrive at that conclusion based on the relative comparison of fossil dates? He has to assume that the known fossil dates are indicative of the relative dates of origin between birds and dromeosaurs. If they weren't, the premise would have no bearing on the conclusion, they would be two dis-jointed ideas. He needs the assumption stated in answer choice (D) to connect the two ideas together.

If he can prove that the origin of birds actually pre-dates the origin of dinosaurs, then he can prove that birds are NOT descendants of dromeosaurs. But given the information in the stimulus, the dinosaur expert's conclusion does not follow, unless some additional assumptions are made.

Negated version of (D):
"Known fossils do NOT indicate the relative dates of origin of birds and dromeosaurs"

If that's the case, then the given premise can no longer act as support for the conclusion. It would severe the connection between premise and conclusion.

5) Eliminate Wrong AC's:
A) Wrong.
B) Wrong.
C) This is where I kicked myself for my loose understanding of the argument. When I first encountered this problem, I mistakenly focused on the terms "known" and "discovered" and pre-phrased an answer concerning faulty evidence. Which made me choose AC (C).

However, as others have pointed out, the complete-ness of fossil records does not seem to be the key issue here. If we want to test whether an answer choice is truly necessary, we can apply the negation test. A negated version of a necessary assumption should undermine the premises' relevance / connection to the conclusion.

Negated Version of (C): Knowledge of dromeosaur fossils and the earliest bird fossils is NOT complete.

So what?

The dinosaur expert's argument could still stand, because the relative comparison of the incompletefossils still indicate that bird fossils are older than dromeosaur fossils. Which could lend support to the conclusion that birds are not descendants of dromeosaurs.

Verify Correct Answer:
Our analysis above should prove that answer choice (D) is in fact necessary.

[Antnat]

Can someone please explain to me why (D) isn't a premise booster?

The way I see it, "... the earliest bird fossils that have been discovered date back tens of millions of years farther than the oldest known dromeosaur fossil" is a premise. In that sense, I shouldn't contest the facts of this sentence. Isn't it factually stated that (known) bird fossils are 10 mil + years older than (known) dromeosaur fossils?
So from this premise, wouldn't I already know about the relative dates of the origins of birds and dromeosaurs based on known fossils, which is what (D) is saying?

Thanks in advance.

[helenaygu]

Can someone please explain to me why (D) isn't a premise booster?

The way I see it, "... the earliest bird fossils that have been discovered date back tens of millions of years farther than the oldest known dromeosaur fossil" is a premise. In that sense, I shouldn't contest the facts of this sentence. Isn't it factually stated that (known) bird fossils are 10 mil + years older than (known) dromeosaur fossils?
So from this premise, wouldn't I already know about the relative dates of the origins of birds and dromeosaurs based on known fossils, which is what (D) is saying?

Thanks in advance.

No. The passage proceeds like this:

1. Paleontologists think birds are descendants of dromeosaurs.
2. They think so b/c fossil records indicate similarities.
3. However, earlier bird fossils are older than the oldest dromeosaur fossils.
4. Paleontologist's claim is false.

With assumption questions, you're better off negating the AC. We are simply trying to make this argument work. If bird fossils predates dromeosaur fossils - but those dates do NOT indicate relative dates of origins - then the author's argument here doesn't work.

You can't assume the "dates of origin" part when the author didn't explicitly state it.

[roflcoptersoisoi]

This is a typical five star curve breaker question, I like many of you felt for trap answer (C)

Argument:
Earliest bird fossils millions of years older than oldest known dromeosaur fossils. There it is not true that birds descended from dromeosaurs

Gap: There aren't undiscovered dromeosaur fossils that date back earlier than the earliest bird fossils.

This seems like a "blocking" necessary assumption question i.e., a correct answer choice will likely negate the possibility of there being undiscovered dromeosaur fossils that date back earlier than the earliest bird fossils in order to preserve the validity of the argument.

(A) This is tempting, it strengthens the argument but it does nothing to bridge gap between fossil records and birds not descending from dromeosaurs and thus is not necessary to the argument
(B) This doesn't need to be true in order for us to conclude that birds did not descend from dromeosaurs.
(C) This is extremely tempting and I fell for it. This is sufficient as in it allows the conclusion to be properly drawn but it is not necessary. We don't need the fossil record to be COMPLETE to substantiate the claim that birds did not descend from dromeosaurs. Even if it were not complete the argument is not completely destroyed, because hypothetically speaking, it could be true that undiscovered dromeosaur fossils date from the same period as the known fossils in which case despite the incompletion of fossil records, the argument would still stand.
(D) I eliminated this on the first go because I thought that it was just a premise booster by confirming the accuracy of dates of fossils. In fact however, the author never states what the RELATIVE dates of origins of the birds and dromeosaurs are, rather he makes an assumption about it (earliest birds are millions of years older than dromeosaurs) to arrive at his conclusion. IF negated the argument is destroyed.
(E) Completely irrelevant.

[roflcoptersoisoi]

Can someone please explain to me why (D) isn't a premise booster?

The way I see it, "... the earliest bird fossils that have been discovered date back tens of millions of years farther than the oldest known dromeosaur fossil" is a premise. In that sense, I shouldn't contest the facts of this sentence. Isn't it factually stated that (known) bird fossils are 10 mil + years older than (known) dromeosaur fossils?
So from this premise, wouldn't I already know about the relative dates of the origins of birds and dromeosaurs based on known fossils, which is what (D) is saying?

Thanks in advance.

You're making the same assumption that the author is making. You wouldn't know the relative dates of origin between the birds and dromeosaurs because we don't know the date of origin of dromeosaurs, only the date of it's oldest known dromeosaur fossils. The author presumes that there aren't older undiscovered dromeosaur fossils and from this makes an erroneous inference as to the relative dates of origin between the two species.

[VishwaksenaM817]

I came across this question in the LR strategy guide and was a bit confused by one of the explanations.
The book said that answer choice C would be the right answer to a sufficient assumption question but is C really sufficient ie: Does this assumption bridge the gap between the premise and the conclusion completely ?
Even if we assume C, we still don’t know if we can trust that the dates the fossils represent when the animals originated. Which means that answer choice C only partially fills the gap.
So how can it be a sufficient assumption ?