It has long been thought that lizards evolves from a group of amphibia

Question

It has long been thought that lizards evolves from a group of amphibians called anthracosaurs, no fossils of which have been found in any rocks older than 300 million years. However, a fossil of a lizard was recently found that is estimated to be 340 million years old. Lizards could not have evolved from creatures that did not exist until after the first lizards. Therefore, lizards could not have evolved from anthracosaurs.

An assumption made in the argument is that there are no

(A) unknown anthracosaur fossils older than 340 million years

(B) unknown lizard fossils older than 340 million years

(C) known lizard fossils that predate some anthracosaur fossils

(D) known anthracosaur fossils that predate some lizard fossils

(E) known lizard fossils whose age is uncertain

NorickHill · Accepted Answer

Lets understand the argument through a timeline.

----------340Years old-------------------300Years Old--------------------present-----------------
 (lizard fossil do exist) (Known anthracosaurs fossil exists) (Analyising the evolution of lizards)

Reasoning:  Since no anthracosaurs fossil predates lizard fossil, lizards can't have evolved from something that came to existence much later than itself.

if something makes us believe that anthracosaurs existed before the oldest traced lizard then conclusion will suffocate.

Assumption:  There doesn't exist any 340 years old anthracosaurs fossil or evidence that is not yet excavated or found.

Ques. Stem: An assumption made in the argument is that there are no

A) unknown anthracosaur fossils older than 340 million years -   This is inline with the thought that no such fossil exist. If we negate this the conclusion will fall apart as it wont be able to claim lizards have not evolved from anthracosaur.
  
(B) unknown lizard fossils older than 340 million years -  irrelevant, single evidence of 340 years old lizard is enough to evaluate the evolution if anthracosaur existence before lizards is not proved. on negating this still the conclusion stands strong.

(C) known lizard fossils that predate some anthracosaur fossils -  Irrelevant; even if there are some it doesn't gives a proof that A evolved from B. It will be like some dogs fossil predates rabbits. Not even linked.
 
(D) known anthracosaur fossils that predate some lizard fossils -  Irrelevant: again "some".

(E) known lizard fossils whose age is uncertain -  Inconsistent: If anthracosaur would be there instead of lizards it could have been the potential contender.

iamdivs · Answer

a) seems to be the correct answer

h31337u · Answer

The answer is D.

An assumption made in the argument is that there are no  (D) known anthracosaur fossils that predate some lizard fossils

dhruvsharma2117 · Answer

I believe the answer to be D. As we do not know any fossil of anthracosaurs older that the lizard so we can safely say that Lizards did not evolve from anthracosaurs

Masterclass_Space · Answer

It has long been thought that lizards evolves from a group of amphibians called anthracosaurs, no fossils of which have been found in any rocks older than 300 million years. However, a fossil of a lizard was recently found that is estimated to be 340 million years old. Lizards could not have evolved from creatures that did not exist until after the first lizards. Therefore, lizards did not have evolved from anthracosaurs.
 
 An assumption made in the argument is that there are no

(A) unknown anthracosaur fossils older than 340 million years (The best option)
The premise is Lizards could not have evolved from creatures that did not exist until after the first lizards and the conclusion is lizards did not have evolved from anthracosaurs so the assumption is anthracosaurs did not exist until 340 million years as the lizard was found estimated around 340 million years.
 
 (B) unknown lizard fossils older than 340 million years: ( incorrect)
The option is about only the premise though assumption is a link between premise and conclusion hence it should discuss the relation between anthracosaurs and lizards.
 
 (C) known lizard fossils that predate some anthracosaur fossils (incorrect)
Rejecting the conclusion that says lizards did not have evolved from anthracosaurs. 
 
 (D) known anthracosaur fossils that predate some lizard fossils (incorrect)
Out of scope as an argument is about the relation of lizards with anthracosaurs instead of anthracosaurs relation with lizard
 
 (E) known lizard fossils whose age is uncertain (incorrect)
Extra assumption based on no evidence

ashish2023 · Answer

no "unknown " means "known", right? so then option A becomes "there are known anthro fossils older than 340 mn years. so option D seems close to correct assumption. Masterclass_Space

Posted from my mobile device

Elevated_person · Answer

I am confused between option A and E. Please help

Dbrunik · Answer

I believe this should say “could not have”, can we please edit to fix?

bb · Answer

You are absolutely right. This appears to be from LSAT (found the exact question online) and updated the text to match it. 
Thank you.

oscarpiastri81 · Answer

E is not relevant. The argument assumes that lizards came before because no evidence is found of the other species 340 mil years ago. What if there are fossils that are not discovered yet? This is not taken into account.

Elevated_person

I am confused between option A and E. Please help

It has long been thought that lizards evolves from a group of amphibia

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It has long been thought that lizards evolves from a group of amphibia

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