#12 - It has long been thought that lizards evolved from a group of amphibians called anthracosaurs

[Administrator]

Complete Question Explanation

Assumption. The correct answer choice is (A).

Answer choice (A): This is the correct answer choice.

Answer choice (B):

Answer choice (C):

Answer choice (D):

Answer choice (E):

This explanation is still in progress. Please post any questions below!

[cutiepie]

Why is answer choice D incorrect. The "no unknown" language confuses me.

[atierney]

Hello,

Well, so for this question, the "unknown" part of the answer choices, which is not explicitly referenced in the argument itself, refers to those fossils that may exist but have not yet been found by archeologists. It's basically that absence of evidence that we should rarely (if ever) take to be evidence of absence. The reason we need an answer choice to include the possibility of unknown fossil record is because we know that the earliest fossil of anthracosaurs is not older than the recent lizard fossil found to be 340 million years old. In fact, it's this piece of evidence that is used in the argument to conclude that the lizard could not have possibly evolved from anthracosaurs. However, what if we find an anthracosaur fossil that is 350 million years old? Then, we have evidence that anthracosaurs preceded the lizards, and therefore become a viable candidate as its predecessor down the evolutionary chain. This is not possible from the known evidence though, but may be possible, unless defended against by the defender assumption in answer choice A, from evidence as yet unknown, but to be discovered.

Hopefully that makes sense. Let me know if you have further questions!

[riabobiia]

Hi!

I'm still a bit confused about answer choice A vs answer choice D. If there are "no known anthra fossils that predate lizard fossils" then doesn't that imply that the anthra fossils that predate lizard fossils are unknown?

What is the difference in the fossils being unknown and known? I think the wording of the question stem + the answer is what's bending my brain.

Or does "no known" in answer choice D imply that there is still evidence out there, we just haven't found it yet?

[srusty]

Hi!

I'm still a bit confused about answer choice A vs answer choice D. If there are "no known anthra fossils that predate lizard fossils" then doesn't that imply that the anthra fossils that predate lizard fossils are unknown?

What is the difference in the fossils being unknown and known? I think the wording of the question stem + the answer is what's bending my brain.

Or does "no known" in answer choice D imply that there is still evidence out there, we just haven't found it yet?

Hi Ria,

For sure, the repetition in phrasing in this question makes it tricky. First, let's break down the question.

Conclusions: Lizards could not have evolved from anthracosaurs.
Why?: We don't have anthracosaur fossils older than 300 million years, but we just found a lizard fossil that is 340 million years ago. A species (lizard) cannot be evolved from a species (anthracosaur) it came before.

For this conclusion to make sense from the premise, the author needs to assume that there are no anthracosaur fossils that would be older than 340 million years. This is what answer choice (A) gets at. The author is assuming that anthracosaur fossils older than 340 million years will never be discovered.

Answer choice (D) states something that the argument does not assume. Answer choice (D) says "there are no known anthracosaur fossils that predate some lizards." This is not an assumption - this is stated in the stimulus itself.

Let me know if that helps!