Although many lines of evidence indicate that birds evolved from groun

Question

Although many lines of evidence indicate that birds evolved from ground-dwelling theropod dinosaurs, some scientists remain unconvinced. They argue that theropods appeared too late to have given rise to birds, noting that Archaeopteryx lithographica—the oldest known bird—appears in the fossil record about 150 million years ago, whereas the fossil remains of various nonavian maniraptor theropods—the closest known relatives of birds—date only to about 115 million years ago. But investigators have now uncovered bones that evidently belong to nonavian maniraptors dating to the time of Archaeopteryx. In any case, failure to find  fossils of a predicted kind  does not rule out their existence in an undiscovered deposit. Skeptics also argue that the fused clavicles (the "wishbone") of birds differ from the unfused clavicles of theropods. This objection was reasonable when only early theropod clavicles had been discovered, but fossilized theropod clavicles that look just like the wishbone of Archaeopteryx have now been unearthed. Finally, some scientists argue that the complex lungs of birds could not have evolved from theropod lungs, an assertion that cannot be supported or falsified at the moment, because no fossil lungs are preserved in the paleontological record.    1  
 1. The primary purpose of the passage is to

A. compare the development of two hypotheses concerning the evolutionary origin of birds
B. suggest revisions to the standard theory of the evolutionary history of birds
C. evaluate the usefulness of fossil evidence in determining the evolutionary history of birds
D. challenge the theory that birds evolved from ground-dwelling theropod dinosaurs
E. respond to criticisms of the theory that birds evolved from ground-dwelling theropod dinosaurs

2  
 2. In the context of the passage, the phrase " fossils of a predicted kind " most likely refers to which of the following?

A. Theropod fossils with fused clavicles
B. Theropod fossils that are similar in structure to Archaeopteryx fossils
C. Theropod fossils dating back more than 150 million years
D. Fossils indicating the structure of theropod lungs
E. Fossils indicating the structure of Archaeopteryx lungs

3  
 3. Which of the following is mentioned in the passage as an argument made by scientists who are unconvinced that birds evolved from theropod dinosaurs?

A. There are no known theropod dinosaur fossils dating from a period after the time of Archaeopteryx.
B. There are no known theropod dinosaur fossils that indicate the structure of those dinosaurs' lungs.
C. Theropod dinosaurs appear in the fossil record about 150 million years ago.
D. Theropod dinosaurs did not have fused clavicles.
E. Theropod dinosaurs had certain bones that look just like those of Archaeopteryx.

mikemcgarry · Accepted Answer

Dear Kritesh , I'm happy to respond. :-)

For #1, think about the flow of the entire passage. Pay close attention to the action of "direction words," words that serve to direct the flow of an argument, either by adding on and amplifying, or by creating a change in direction by a contrast word. Although many lines of evidence indicate that birds evolved from ground-dwelling theropod dinosaurs, some scientists remain unconvinced. Ambiguous opening sentence, typical of academic writing--the author has not yet shown his hand, what he believes. They argue that .... so far, we don't know what the author really thinks . . . BUT investigators have now uncovered Ah ha! That word " but " is HUGE! This is a very classic argument format: " My opponent thinks X, BUT I think Y " This is a very effective strategy in argument, because the implication is that I know & understand my opponent's argument but I know better. The next sentence " in any case ," which is a way of adding on an additional point. This strengthens his response to the first objection. Now, another round: Skeptics also argue . . . Again, the author is stating the opinions of those with whom he disagrees, more objections. This objection was reasonable when . . . but . . . Rhetorically very effective: he gives a partial concession to the opponents view--yes, it worked in the past, but it's nonsense to believe it now! " Finally " = another strong summary word. Throughout the whole passage, the author was stating the objections to the theory and then was arguing against those objections. He was defending the theory that " birds evolved from ground-dwelling theropod dinosaurs ." Anything that states the meaning of the paragraph should capture this back-and-forth, objection and then response to objection, which happens a few times. The author is not simply evaluating, which implies a neutral agenda. The author has constructed sophisticated argumentative structures to respond to objections. Thus, the best answer to #1 is (E) respond to criticisms of the theory that birds evolved from ground-dwelling theropod dinosaurs For #2, look at that section of the text: They argue that theropods appeared too late to have given rise to birds, noting that Archaeopteryx lithographica—the oldest known bird—appears in the fossil record about 150 million years ago, whereas the fossil remains of various nonavian maniraptor theropods—the closest known relatives of birds—date only to about 115 million years ago. This is objection #1: birds are old, 150M years old, and nonavian maniraptor theropods are not that old. But investigators have now uncovered bones that evidently belong to nonavian maniraptors dating to the time of Archaeopteryx. First, specific response to objection #1 In any case, failure to find fossils of a predicted kind does not rule out their existence in an undiscovered deposit. More general response to the objection. Let's think about the author. The author is defending the theory that " birds evolved from ground-dwelling theropod dinosaurs ." Obviously, what would strength his case the most is if scientist found definitive evidence of ground-dwelling theropod dinosaurs from the time of the first birds (150 MYA) or older. Short of that, he argues that the current absence of these are simply due to the fact that we haven't discovered them yet. The particular fossils that interest him are " ground-dwelling theropod " as old as birds (150 MYA) or older. The best answer is (C) Theropod fossils dating back more than 150 million years Does all this make sense? Mike :-)

ShashankDave · Answer

Please explain why 2. is not B.

VenoMfTw · Answer

There was an objection raised by the scientists that there was no record of fossil (theropods) found about 150 M years ago.
But since in new investigations fossils(theropods) were found that dated back 150 M years, the scientists claim was refuted.

On this note, author argues that   "Even if there was no fossil found, which dated back 150M years, scientists cannot completely override any future possibility on finding one"

"fossils of a predicted kind" --> referring to the new evidence (theropods fossils dating back 150)

Skywalker18 · Answer

-The author presents a point of debate
- The author then points out the challenges presented by scientists on a certain topic
- The author then responds to the challenges presented by the scientists

Took 5 mins 40 seconds in total , including 2 mins to read

1. The author clearly states the criticisms of scientists and responds to each one of those criticisms. Hence option (E) is the best answer choice.

2. "noting that Archaeopteryx lithographica—the oldest known bird—appears in the fossil record about 150 million years ago, whereas the fossil remains of various nonavian maniraptor theropods—the closest known relatives of birds—date only to about 115 million years ago. But investigators have now uncovered bones that evidently belong to nonavian maniraptors dating to the time of Archaeopteryx. In any case, failure to find fossils of a predicted kind does not rule out their existence in an undiscovered deposit."

The fossils dating back to 150 years ago are what are being referred to and hence option (C ) is the right answer.

3. "Skeptics also argue that the fused clavicles (the "wishbone") of birds differ from the unfused clavicles of theropods"

Answer D

arunavamunshi1988 · Answer

Hi, I did not understand how come the ans of qstn 3 is D. will the sentence 'Skeptics also argue that the fused clavicles (the “wishbone”) of birds differ from the unfused clavicles of theropods' imply that 'Theropod dinosaurs did not have fused clavicles.'? It might also be possible that Theropod dinosaurs have both fused and unfused clavicles but here the comparison is drawn only with unfused clavicles for some reason.

Kritesh · Answer

Total time taken 8 mins

1.C
2.B
3.D

mikemcgarry  - Could you please explain that for questions 1&2 why the answer is E & C .

Adi93 · Answer

Hi  mikemcgarry

Can you please explain question 3.I chose option B..I dont know why the answer is D.

Thanks

mikemcgarry · Answer

Dear gamerguy0074 , I'm happy to respond. :-)

Here's Q#3: 3. Which of the following is mentioned in the passage as an argument made by scientists who are unconvinced that birds evolved from theropod dinosaurs? A. There are no known theropod dinosaur fossils dating from a period after the time of Archaeopteryx. B. There are no known theropod dinosaur fossils that indicate the structure of those dinosaurs' lungs. C. Theropod dinosaurs appear in the fossil record about 150 million years ago. D. Theropod dinosaurs did not have fused clavicles. E. Theropod dinosaurs had certain bones that look just like those of Archaeopteryx. Since you ask about (B) and (D), I'll just discuss those two. B. There are no known theropod dinosaur fossils that indicate the structure of those dinosaurs' lungs. This is a very sophisticated trap answer. Here's the relevant part of the passage: Finally, some scientists argue that the complex lungs of birds could not have evolved from theropod lungs, an assertion that cannot be supported or falsified at the moment, because no fossil lungs are preserved in the paleontological record. These skeptic scientists do have an argument about lungs, but the fact that " no known theropod dinosaur fossils that indicate the structure of those dinosaurs' lungs " does not in any way constitute part of these skeptics' argument. Quite to the contrary, this is the reason that their argument can be neither supported nor falsified. This fact comments on the possible evaluation of their argument, not on the content of their argument. Does this distinction make sense? D. Theropod dinosaurs did not have fused clavicles. Very clear proof text: Skeptics also argue that the fused clavicles (the "wishbone") of birds differ from the unfused clavicles of theropods. This is, quite directly, something that the skeptics argue. Does this make sense? Mike :-)

Nunuboy1994 · Answer

The only thing I don't understand about question 3 is that is says "skeptics" rather than "scientists." I narrowed down question 3 to B and D however I felt that skeptics could have referred to a different group of people? Or I suppose with question 3 it would be better to eliminate B because that statement is not necessarily supported by the passage? It doesn't say anywhere that scientists are challenging the lack of fossil lungs.

sananoor · Answer

Can anyone explain that why the answer of question 3 is D..why not A?

GMATNinja · Answer

The passage states that "some scientists remain unconvinced." In other words, some scientists are skeptical. Thus, those scientists are the skeptics.

The author presents three arguments made by scientists who are unconvinced that birds evolved from theropod dinosaurs:

1) Theropods appeared too late to have given rise to birds.
2) The fused clavicles (the “wishbone”) of birds differ from the unfused clavicles of theropods.
3) The complex lungs of birds could not have evolved from theropod lungs.

Choice (D) specifically refers to the second item in the list.

Choice (B) is not an argument made by the skeptics. Rather, it is a statement made by the author to show that #3 in the list cannot be supported or falsified at the moment.

As for choice (A), notice the word "after". There ARE certainly theropod fossils dating from  after  the time of the Archaeopteryx. The passage tells us that 150 million-year-old Archaeopteryx fossils have been found and that 115 million-year-old theropod fossils have been found. The problem, according to the skeptics, is that there are no known theropod dinosaur fossils dating from a period BEFORE the time of the Archaeopteryx.

Choice (D) is the best answer.

gmat8998 · Answer

jennpt  question 3: 'Skeptics also argue that the fused clavicles (the “wishbone”) of birds differ from the unfused clavicles of theropods' imply that 'Theropod dinosaurs did not have fused clavicles.'?
choice C :Looks like a very close choice in this one-->
Theropod dinosaurs appear in the fossil record about 150 million years ago.

BrightOutlookJenn · Answer

Hi  gmat8998

Thanks for the tag. For this question, it could help to first get very clear about what the question is asking you to find.
 (bolding is mine)

OK, so we want a piece of evidence brought up by the people who DO NOT think that the therapods were the ancestors of birds. Or to put it another way, evidence raised to suggest that therapods COULD NOT BE the ancestors of birds.

Answer choice C actually does the opposite of what you are looking for, so it can't possibly be our answer.

When does the author discuss the age of the therapod fossils? Twice. 
The first time, he brings up that we had only found therapod fossils that are 115 million years old. Why does he bring this up? To explain one argument of the skeptics, who say that therapods could not have been the ancestor of birds (which first started appearing 150 million years ago.)
The second time, he says "But investigators have now uncovered bones that evidently belong to nonavian maniraptors dating to the time of Archaeopteryx." Why does he bring up this fact? To argue  against  the skeptics, and say that now we have fossils old enough to suggest that therapods are at least as old as the oldest bird - both now 150 million years old.

Answer choice C is describing the second piece of evidence, which is the one that argues AGAINST the critics and is used to say that therapods actually COULD have been the ancestors of birds.
If answer choice C had said "115 million" instead of "150 million", then it would have been a relevant answer choice.

Let me know if this helps, and also if you can determine where the error was in your thinking.

sayan640 · Answer

Hi  GMATNinja   VeritasKarishma   jennpt

The argument put forward by skeptics ( scientists who believed that birds could not have evolved from dinosaurs) , is :-  "The fused clavicles (the “wishbone”) of birds differ from the unfused clavicles of theropods." 
How does it mean that "  Theropod dinosaurs did not have fused clavicles."  ?  Nowhere the passage mentions that "Theropod dinosaurs did not have fused clavicles."   VeritasKarishma   GMATNinja

Please explain.

Also Is option A incorrect because it is a wrong statement and certainly not an argument put forward by skeptics ?
It says that 'There are no known theropod dinosaur fossils dating from a period after the time of Archaeopteryx." 
This is a wrong statement as we know from the passage that there are indeed theropod dinosaur fossils which are 115 years old and 150 years old.

KarishmaB · Answer

"The fused clavicles (the “wishbone”) of birds differ from the unfused clavicles of theropods."

You are given that birds have fused clavicles. You are also given that theropods have UNFUSED clavicles (so their clavicles are not fused together). So you are given that clavicles of theropods were not fused together.

KarishmaB · Answer

Option A is wrong because the critics' argument is that there are no known theropod fossils from BEFORE the time of Archaeopteryx.

" theropods appeared too late  to have given rise to birds, noting that Archaeopteryx lithographica—the oldest known bird—appears in the fossil record about 150 million years ago, whereas the fossil remains of various nonavian maniraptor theropods—the closest known relatives of birds—date only to about 115 million years ago. But investigators have now uncovered bones that evidently belong to nonavian maniraptors dating to the time of Archaeopteryx."

The passage tells us that theropods appeared late (115 million years ago) while bird appeared earlier (150 million years ago). So birds could not have evolved from theropods. But now, theropods dating 150 million years ago have been found. Anyway, no fossils found doesn't mean no fossils exist.

sayan640 · Answer

Hi  VeritasKarishma

Thanks for clearing my doubt. I dint understand the significance of your last sentence " Anyway, no fossils found doesn't mean no fossils exist."
My reasoning is as follows ; Please correct me if it's wrong.....

Option A is wrong because the critics' argument is that "there are no known theropod fossils from BEFORE the time of Archaeopteryx" whereas option A says "There are no known theropod dinosaur fossils dating from a period AFTER the time of Archaeopteryx." 
What option A says is neither correct factually ( As we have found theropod dinosaur fossils which are 115 years old and 150 years old ) nor is it the argument put forward by the critics.

That's why option A is incorrect.
Please let me know whether my understanding is correct or not. 
 VeritasKarishma   GMATNinja

KarishmaB · Answer

"No fossils found doesn't mean no fossils exist" means that just because something hasn't been found, you cannot say it doesn't exist. It is not valid reasoning. Just because a theropod fossil older than 150 million years hasn't been found doesn't mean that there were no theropods in that time. Perhaps the fossil hasn't been discovered yet.

Anyway, your logic is correct.

Rickooreo · Answer

I got Q2 and Q3 wrong and unable to understand the reasoning for right answer...It would be great if anyone can help

For Q2, Correct answer is C but the options says "more than" 150 mn but the para says "Archaeopteryx lithographica—the 
oldest known bird—appears in the fossil record about 150 million years ago". I rejected option C, because it says more whereas para required about. 
Also to understand how to eliminate B.

For Q3, last sentence of the para does mention option B and this is unresolved, the question is asking "argument made by scientists 
(minority) who are unconvinced" now uncovinced doesnt means that agrument is right or wrong. It has to be presented by them and option B is presented as per last sentence of the para.

Although many lines of evidence indicate that birds evolved from groun

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Although many lines of evidence indicate that birds evolved from groun

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