Recently discovered fossil evidence casts doubt on the evolutionary th

Here is a great explanation from from David@VeritasPrep - GMAT Instructor

"This question is from the October 1993 LSAT the first Logical Reasoning Section, number 11.

This is a method of reasoning question, it asks you to describe how the argument proceeds. This is a type of question that does appear on the GMAT and is one of the "m"s in the Veritas SWIMMER method.

Method of reasoning questions are some of the best questions to study to improve your overall critical reasoning skills. They help you to understand how arguments are structured - how they are supposed to lead to their conclusion.


You can start this type of question as you would any "normal' - meaning not inference and paradox. So start by identifying the conclusion. In this case the conclusion comes at the very beginning of the argument. This would be rare for a GMAT question! So the conclusion is

"Recently discovered fossil evidence casts doubt on the evolutionary
theory that dinosaurs are more closely related to reptiles than to
other classes of animals."

Now we want to look to the evidence for this conclusion. The rest of the passage is really the evidence - several examples of things that are not true of present-day reptiles and are true of present day birds and other warm-blooded animals.

So that is what the argument is doing - arguing for a conclusion about a type of animal that is long extinct by comparing that type to two current types of animals.

This is what answer choice E says, "presenting evidence that a past phenomenon is more similar to one
rather than the other of two present-day phenomena." Please do not get caught up in the term phenomenon. On the GMAT and the LSAT the word phenomenon has very little real meaning - it only means a thing or an event.

In this case the past phenomenon is dinosaurs and the present phenomena are warm-blooded creatures and cold-blooded creatures".

He made the analysis so simple

OFFICIAL EXPLANATION

(A) No. None of the evidence mentioned in the passage is refuted.

(B) No. This is the second-best answer. Although the passage does state several general principles (e.g., “all fast-breathing animals are warm-blooded), this is done as part of a series of evidence rather than directly used to deduce the conclusion of the argument.

(C) No. The passage is casting doubt on a present claim about the past.

(D) No. This is too strong. The passage merely implies, “fossil evidence casts doubt on the evolutionary theory that dinosaurs are more closely related to reptiles than to other classes of animals.”

(E) Yes. The passage presents a sequence of evidence indicating that dinosaurs were similar to modern birds and dissimilar to modern reptiles.




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The main point of the argument is that recently discovered dinosaurs' fossils support that dinosaurs were warm blooded (like birds), not cold blooded (like reptiles) as previously thought.
Then it goes on to give 4 specific points why it is likely that dinosaurs were warm blooded. The author uses present day evidence (warm blooded vs cold blooded animals today) to establish something about the past (how dinosaurs were millions of years ago)

(A) attempting to justify one position by demonstrating that an opposing position is based on erroneous information

The passage attempts to justify "dinosaurs were warm blooded" and oppose "dinosaurs were cold blooded".
The passage does not give any erroneous info on which cold blooded position is based. Instead, it gives recent discovery evidence that suggests warm blooded.

(B) establishing a general principle that it then uses to draw a conclusion about a particular case

The argument does not really establish any general principle. A general principle would be something like "only warm blooded animals have hollow bones".
The author gives us facts about today - today only warm blooded animals have hollow bones - and says that since dinosaurs' fossils show that they had hollow bones, so dinosaurs must have been warm blooded etc.

(C) dismissing a claim made about the present on the basis of historical evidence

It is the other way around. He makes a claim about the past based on present day evidence.

(D) assuming that if all members of a category have a certain property then all things with that property belong to the category

This would have been true if the author had said that all warm blooded animals have hollow bones and since dinosaurs had hollow bones too, dinosaurs must have been warm blooded. But that is not what he says. He says that today ONLY warm blooded animals have hollow bones (no cold blooded animals have hollow bones) so dinosaurs must have been warm blooded. The same for all other points he mentions too. He says ALL fast breathing are warm blooded so dinosaurs must have been warm blooded too.

(E) presenting evidence that a past phenomenon is more similar to one rather than the other of two present-day phenomena

Correct. He says that dinosaurs were more similar to warm blooded animals than to cold blooded animals.

Answer (E)
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E for me too
phenomena according to Webster dictionary: an observable fact or event
In this case, the past fact would be "dinosaurs" and the present two facts would be "reptiles" and "birds"

I feel D is convincing. I could not understand E but Paul's explanation is very nice.

The argument says that recently discovered fossil evidence ( of one dinosaur ) is more similar to birds than to any other aninal. If a generalization has to be made then it is necessary to assume that if one animal belongs to a catagory and all the animals with same characteristics must also belong to the same catagory.

Can any one refute this please...

Let me try to refute..

A snake is a reptile which bites.

Characteristic being "it bites".

A dog bit the boy.

=> Dog is a reptile ?

Specifically, with re to the choice D, draw two sets P (Mbr of same category) and Q (property), with Q as a superset of P.
All P is Q..but all Q is not P.

hi ashwyn,

We are not debating whether the argument is wrong or right. The Q is asking how does the argument proceed.

Anand.

[quote="anandnk"]I feel D is convincing. I could not understand E but Paul's explanation is very nice.

The argument says that recently discovered fossil evidence ( of one dinosaur ) is more similar to birds than to any other aninal. If a generalization has to be made then it is necessary to assume that if one animal belongs to a catagory and all the animals with same characteristics must also belong to the same catagory.

Can any one refute this please...[/quote]

Anand,

Pls read Option D again. There is a slight difference between ur statement above and choice D.

Choice D says- if ALL members of a category have a certain property then ALL THINGS with that property belong to the category

What u have stated is a REQD and necessary assumption, but this is not what is stated in Choice D.

Ur interpretatioin- if ONE animal belongs to a catagory and ALL animals with same characteristics must also belong to the same catagory.
is perfectly true and necessary.

Pls let me knw if the above is unclear or u dont agree. Tks.

Hi Ashwyn

I will give it to you. I guess D has a flaw in itself.
More importantly the author is giving evidence. I believe E makes more sense. I just thought properties of birds cannot be called the phenomenon.

Anand.

I like the explanations you guys gave, but I think I'd go with B on this one, if I saw this Q on the exam. My reasoning:

If the author states that the Din. are not closely related to Reptiles, he must show why previous claims were made about the similarity of Din and Reptiles. Also, one might question the evolution of present day reptiles, what were they like back during the times of evolution. Similarly, while the author demonstrates with examples that D had many characteristics of birds and other warm blooded animals, I am still not sure what the previous claims were based on. Maybe Din breath like birds, have hollow bones and so on, but they are still more closely related to Reptiles. E is most definitely a convincing statement, but I still believe that the author establishes a principle--dinosaurs cant be resmble reptiles-b/c they have many carachteristics of warm blooded animals, which is not true Din can still belong to the reptile family. Cat's breath thru mouth, and do many other things like dogs, yet they dont belong to the canine family. Anyway, thats my take on it. Feel free to correct any flaws in my reasoninig.

Needed a little editing. This question is really tough in my opinion, and I REALLY dont like the "general principle" phrase, unless we can assume that the first statement can be called a general principle, which is what I did.

Is this really what you call a principle or is it just a mere claim the author is trying to prove?

Paul,

I agree with E, but I am still not sure why B is wrong, if it is. Yes, I was a little hesistant to call it a principle. Id like to see the official explanation. The core of my reasoning was that, while it is possible that Din resemble Birds, we still dont know, but it is possible that Din have greater similarity with Reptiles. If that is a phenomenon, then I would agree with E. But using the same reasoning, we could call a hundred of accepted principles a phenomenon. There are many birds that can't fly, but we still classify them as birds, is that a phenomenon? Hmm, maybe I am taking it too far, or even in the wrong direction.

(E) presenting evidence that a past phenomenon is more similar to one rather than the other of two present-day phenomena

May I ask what is the past phenomenon refer to? and the two present-day phenomena?

According to the OE, the past phenomenon is the dinosaur and the two present day phenomena are reptiles and birds.

Hi,

presenting evidence that a past phenomenon is more similar to one rather than the other of two present-day phenomena

evidence:--
Fossils show that some dinosaurs had hollow bones-a feature
Dinosaurs had well-developed senses of sight and hearing, which is not true of present-day cold-blooded creatures like reptiles.
The highly arched mouth roof of some dinosaurs would have permitted them to breathe while eating, as fast-breathing animals, such as birds, need to do.
Today, all fast-breathing animals are warm-blooded. Finally, fossils reveal that many dinosaurs had a pattern of growth typical of warm-blooded animals.

a past phenomenon:-
these evidences talk of a past phenomenon- Dinasours/evolution of dinasours

more similar to one of two present-day phenomena:-
birds..

rather than the other of two present-day phenomena:-
reptiles
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Hello chetan2u,

I agree with the explanation provided by you. Can you let me know how can we eliminate D?

D) assuming that if all members of a category have a certain property then all things with that property belong to the category

category - warm-blooded animals/growth of warm-blooded animals

property - hollow bones or breathe while eating

all things with that property - dino with the above property

belong to the category - Finally, fossils reveal that many dinosaurs had a pattern of growth typical of warm-blooded animals.

warriorguy
Here's why- the argument talks about 'some' (not all) members of a category ('dino').

My question on E.

"two present-day phenomena" - What are these two?

Fc733

The past phenomenon is the evolution of dinosaurs/dinosaurs themselves

The two present-day phenomena are:

1) birds (similar to dinosaurs)
2) reptiles (less similar to dinosaurs)

Hope that helps