Since at least 1868, paleontologists have been arguing over

Question

Since at least 1868, paleontologists have been arguing over whether or not birds evolved from dinosaurs. In the late 1960s, a scientist from Yale University named John Ostrom declared there were 22 features in the skeletons of meat-eating dinosaurs that were also seen in birds but not in any other animals. By the year 2000, 85 such characteristics unique to dinosaurs and birds had been discovered. Some very vocal critics continue to oppose the theory, but this skeletal evidence strongly supports the idea that dinosaurs are the direct ancestors of modern birds.

Which of the following, if true, would allow the conclusion of the argument to be more properly drawn?

(A) It is impossible to tell for certain by examining the fossil record whether dinosaurs were warm-blooded like birds or cold-blooded like reptiles.

(B) Therapod dinosaurs evolved feathers in place of scales because feathers conferred greater protection against the cold.

(C) The existence of so many uniquely linked characteristics cannot be explained by convergent evolution, the development of similarities in separate lineages through the operation of similar selective factors on both lines.

(D) Several of the supporters of the theory that birds evolved from dinosaurs are paleontologists who are highly regarded in their field.

(E) The earliest "feathered dinosaur" fossil found has been dated at 129 million years old, while the earliest "true bird" fossil has been dated at 150 million years old.

vivesomnium · Answer

Answer should be C. By negating an alternate explanation, the statement supports the conclusion.

BlueRobin · Answer

Answer should be C. Convergent evolution states two species need not be related to share certain traits. So, If this theory cannot explain the findings, then the species must be dependent.

Jacksparrow1906 · Answer

Why not B? It strengthens the conclusion by giving a reason why a certain dinosaur grew feathers.

rphardu · Answer

Premises : 1868 : wht din. anc. birds 1960 : J.O. dec 22 Ft. din & brd comm not in any ot animal 2008 : 85 ft. Conc. Critics ops but sklt evd supp idea of anc. Question is asking new premise or assumption which can add for better conclusion: 1. It is impossible to tell for certain by examining the fossil record whether dinosaurs were warm-blooded like birds or cold-blooded like reptiles - This is explaining if we want to infer something about dinosaurs but here we are concentrating on birds. 2.Therapod dinosaurs evolved feathers in place of scales because feathers conferred greater protection against the cold. - We are not talking about specific "Therapod dinosaurs", considering characterstics from dinosaurs family. 3.The existence of so many uniquely linked characteristics cannot be explained by convergent evolution, the development of similarities in separate lineages through the operation of similar selective factors on both lines. - so here mentioned that C.E. is not able to explain unique characterstics, right because if it can, then there won't be any critics. 4.Several of the supporters of the theory that birds evolved from dinosaurs are paleontologists who are highly regarded in their field. - We don't doubt on palentologist's ability. 5.The earliest "feathered dinosaur" fossil found has been dated at 129 million years old, while the earliest "true bird" fossil has been dated at 150 million years old. - Again talking about one type of dinosaur. "feathered dinosaur", you started about 129 million but other dinosaur can start much before 150 million so you should keep quiet

shashankp27 · Answer

The answer lies in your sentence ...

The statement talks about only a  certain species of dinosaur  ... while the conclusion is for the dinosaurs 'in general'.

avohden · Answer

This question showed up on Kaplan's question of the day. The OA is C. Kaplan provided the following explanation.

At the end of the stimulus, we read that "this skeletal evidence strongly supports the idea that dinosaurs are the direct ancestors of modern birds." In other words, the identification of 85 skeletal features found only in dinosaurs and birds supports the idea that birds evolved from dinosaurs. The assumption here is that nothing else could account for the existence of these common skeletal characteristics. Choice (C), the correct answer, indicates that one possible alternative explanation is in fact false; this confirms the assumption that no other explanation for the linked characteristics is possible and thus supports the argument that such skeletal features prove the evolution of birds from dinosaurs.

Of the wrong answer choices, choices (A) and (B) are outside the scope; the argument concerns skeletal features rather than blood issues or the development of feathers. The existence of feathers in some dinosaurs might be a linkage between dinosaurs and birds, but it is not an assumption upon which this argument depends. Choice (D) is also irrelevant—it may very well be true that several of the opponents of the bird-dinosaur theory are also paleontologists who are highly regarded in their field. Such appeals to authority are rarely correct on the GMAT. Finally, choice (E), if anything, weakens the argument. The fact that the earliest "true bird" fossil is older than the earliest "feathered dinosaur" would seem to argue against the bird-dinosaur theory.

Helium · Answer

This question stem asks for a piece of evidence that would better allow the conclusion to be drawn, in other words, that would strengthen the argument. This is a Strengthen question.

The author's argument is that the existence of 85 skeletal features found only in dinosaurs and birds supports the idea that birds evolved from dinosaurs. The assumption here is that nothing else could account for the existence of these common skeletal characteristics.

(C), the correct answer, indicates that one possible alternative explanation is in fact false; this tends to confirm the assumption that no other explanation for the linked characteristics is possible and thus supports the argument that such skeletal features prove the evolution of birds from dinosaurs.

(A) is irrelevant; since scientists can't tell whether dinosaurs share yet another characteristic with birds, it neither helps nor hurts the argument.

(B) is also irrelevant, because the argument is about the link between skeletal features and the idea that birds evolved from dinosaurs. Information about feathers, therefore, does not relate to the link between the evidence and conclusion.

(D) is also irrelevant - it may very well be true that several of the opponents of the bird-dinosaur theory are also paleontologists who are highly regarded in their field.

(E), if anything, weakens the argument. The fact that the earliest "true bird" fossil is older than the earliest "feathered dinosaur" would seem to argue against the bird-dinosaur theory.

Posted from my mobile device

egmat · Answer

Hi there,

Let's break this argument down step by step.

The argument's structure is: 
-  Evidence:  Dinosaurs and birds share  85  skeletal features not found in any other animals.
-  Conclusion:   Therefore , dinosaurs are the direct ancestors of modern birds.

The question asks: what would allow the conclusion to be MORE PROPERLY drawn? In other words, what assumption or additional fact would strengthen the link between the evidence and the conclusion?

Here's the critical gap:  Just because two groups share unique features doesn't automatically mean one descended from the other.  There's a well-known alternative explanation called  convergent evolution  — where two completely unrelated species independently develop similar traits because they face similar environmental pressures. Think of how both bats and birds have wings, yet bats didn't evolve from birds.

So the argument has a hole: What if dinosaurs and birds independently evolved these  85  features?

Now let's evaluate the choices:

A  — Warm-blooded vs. cold-blooded is irrelevant to the skeletal evidence argument. It neither helps nor hurts.

B  — Feathers replacing scales is interesting but doesn't address whether the shared features prove direct ancestry.

C  —  CORRECT.  This directly plugs the hole. It says  convergent evolution  CANNOT explain  85  shared unique features. If the only other explanation is eliminated, then direct ancestry becomes the only viable conclusion.

D  — The reputation of scientists is an  appeal to authority , not a logical strengthening of the evidence.

E  — This actually  WEAKENS  the argument! If true birds appeared  150  million years ago but feathered dinosaurs only  129  million years ago, then birds came FIRST — making it impossible for dinosaurs to be their ancestors.  Common mistake : don't pick an answer that goes in the opposite direction of what the question asks.

Key takeaway:  When an argument claims X caused Y based on a correlation or shared features, always ask — is there an alternative explanation? The correct strengthen answer will often eliminate that alternative explanation.

Answer: C

Since at least 1868, paleontologists have been arguing over

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Since at least 1868, paleontologists have been arguing over

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