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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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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?

It is impossible to tell for certain by examining the fossil record whether dinosaurs were warm-blooded like birds or cold-blooded like reptiles.
Therapod dinosaurs evolved feathers in place of scales because feathers conferred greater protection against the cold.
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.
Several of the supporters of the theory that birds evolved from dinosaurs are paleontologists who are highly regarded in their field.
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.






c

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Hey Varun,

Great question here. Let's start by looking at the conclusion/premise:

Conclusion: Dinosaurs = ancestors of birds
Premise: Tons of features in common

At first glance, this is a great argument. So really we simply need an assumption that strengthens the link between features implying ancestry. After all, dinosaurs and people both have/had "legs," but that doesn't make dinosaurs the direct ancestors of people.

(A) This doesn't help the argument at all! It would be helpful if we could work it out, and if it turned out dinosaurs were warm-blooded like birds.

(B) This strengthens a bit, connecting birds and dinosaurs, but not as much as you'd think. Remember, we already have 85 shared characteristics. This just gives us one more.

(C) CORRECT. This tells us that this many shared characteristics can't be a coincidence/convergent evolution. Very good to know. If we negate this, the argument is ruined: "The existence of so many uniquely linked characteristics can be explained by convergent evolution, the development of similarities in separate lineages through the operation of similar selective factors on both lines."

(D) This strengthens a bit, but it's only "several...paleontologists," which isn't nearly enough to make the conclusion definitive.

(E) This is terrible for the argument, because it shows birds as predating the dinosaurs that are supposed to be their ancestors!

Hope that helps!

-t

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