Q6 - Recently discovered bird fossils

[haeaznboiyoung]

Narrowed it down to A and E. Chose A because it sounded better but just can't see how E is wrong yet.

C: So these newly discovered fossils show that no bird could have descended from any dino

I usually have problems with flaws like this... whether the argument itself is flawed in the way it brings about the conclusion OR that it ignores an alternative possibility (essentially weaken.) In this case, I feel like these two answers provide both scenarios.

A of course points out the conclusion goes way too far from the evidence it provides. But does E not provide an alternative possibility? That the conclusion can be false because both dinos and birds could have both descended from a common ancestor (another dinosaur perhaps?). I thought that maybe that would be too big of an inference to make that such a common ancestor could be another dinosaur but doesn't the fact of the answer saying "ignores the possibility" essentially allow us to bring in new information?

[bbirdwell]

Conclusion: birds did not descend from dinos

(E): maybe dinos and birds both descended from something else

There's no friction here. These statements are actually in accord. See what I mean?

This answer would more appropriately fit the "alternative possibility" scenario you described if the conclusion argued that birds DID descend from dinos.

[eunjung.shin]

I chose A debating between A and E. How can you draw the answer A from "recently discovered bird fossilS" it is not just one fossil and we actually dont know how many there are. Then how can you be sure the flaw is drawing a generalization that is broder than is warranted?


Thanks a lot!

[shirando21]

To better understand the choice A, what can be drawn and warranted by the findings cited?

[bbirdwell]

Great question! Nothing more than what is explicitly stated!

In other words, we know only two things from the statements:

1. the new bird fossils are older than the dino fossils,
2. the birds are generally (mostly) claimed to have descended from dinos.

Even more specific to your question, "the findings" are only the first: the new bird fossils are older than the dino fossils.

[smsotolongo]

If I can take a stab at why E is wrong and not A. Answer E says that BOTH descended from a common ancestor. The conclusion in the stimulus is that no bird descended from any dinosaur. If they have a common ancestor in which they both sprung from that strengthens his argument. If they are traced to a common ancestors then birds did not descend from dinosaurs. Answer choice A addresses the fact that he went to far with his conclusion. Perhaps he's right, but the theory that birds descended from dinosaurs is still correct if it happened earlier than we thought.

[erikwoodward10]

I kept A on my BR, because it sounded OK. But I couldn't disprove D so I chose it. Why is D wrong? Bird fossils were found 20 million years before bird like dinosaurs. The conclusion states that no bird descended form any dinosaur, and we need to find a flaw.

Well, what if the evolutionary chain (of the same species) went something like this:

80 Million years ago: Bird ---> 60 MYA: Dinosaur ---> Today: Bird

In this case the information in the stimulus is correct, and the conclusion is improperly drawn. It makes perfect sense to me... but according to 7sage only 2% of test takers select D. So what am I not seeing here? Is it really that ridiculous to assume that a bird couldn't evolve into a dinosaur in 20 million years? I mean, we all evolved from single cell organisms so it doesn't seem all that crazy to me.

Additionally, this same logic should allow E to be correct. E never specifies that they evolved along separate evolutionary trees from a common ancestors, like humans and horses for example. So the answer choice could be understood to say that birds and dinosaurs evolved from a common ancestor along the same line, for example, another bird 80 million years ago!

Maybe it's ridiculous to think that even if a bird like creature evolved into a dinosaur, and then into another bird, that the two bird like species were actually the same... Maybe I'm haven't slept in a week because I've been studying for the LSAT non-stop!

Help!

[rachel.zuliniak]

Here is how I understood the question (I've paraphrased):

Conclusion: No birds descended from any dinosaur.

Why? These newly found bird fossils older than the birdlike dinosaur fossils.

A) Yes! This single piece of evidence could have a ton of explanations. It's a huge jump from the premise to the conclusion. A sillier (and slightly imprecise) example that might make it clearer: My can of beans has an expiry date before (i.e. it's older than) than my loaf of bread. Therefore, canned beans were invented before sliced bread.

E) This answer seems to fit the "common sense trap" the best. If I had to guess this would be my answer. However, the wording here is important as to why it is not the correct logical flaw. "Ignores that they are descended from a common ancestor". The argument doesn't do this. It only says birds are not descended from dinosaurs. The argument allows the possibility that they had a common ancestor - maybe they evolved from the same type of bacteria or some sort of other flying creature. The argument only rules out a single possibility (bird and dinosaur).