Anthropologist: It was formerly believed that prehistoric Homo sapiens

Question

Anthropologist: It was formerly believed that prehistoric Homo sapiens ancestors of contemporary humans interbred with Neanderthals, but DNA testing of a Neanderthal’s remains indicates that this is not the case. The DNA of contemporary humans is significantly different from that of the Neanderthal.

Which one of the following is an assumption required by the anthropologist’s argument?

(A) At least some Neanderthals lived at the same time and in the same places as prehistoric  Homo sapiens  ancestors of contemporary humans.
(B) DNA testing of remains is significantly less reliable than DNA testing of samples from living species.
(C) The DNA of prehistoric  Homo sapiens  ancestors of contemporary humans was not significantly more similar to that of Neanderthals than is the DNA of contemporary humans.
(D) Neanderthals and prehistoric  Homo sapiens  ancestors of contemporary humans were completely isolated from each other geographically.
(E) Any similarity in the DNA of two species must be the result of interbreeding.

Resource: LSAT

GMATNinja · Accepted Answer

The author uses the evidence that "the DNA of contemporary humans is significantly different from that of the Neanderthal" to conclude that prehistoric Homo sapiens ancestors of contemporary humans did NOT interbreed with Neanderthals. In other words, according to the author, if the PHS ancestors of contemporary humans HAD interbred with Neanderthals, the DNA of the Neanderthal would have been passed down to contemporary humans and there would not be significant differences between the DNA of contemporary humans and the DNA of the Neanderthal.

If we negate choice (C), that would mean that the differences between the DNA of contemporary humans and the DNA of their PHS ancestors are COMPARABLE to the differences between the DNA of contemporary humans and the DNA of the Neanderthal. This would tells us that we CANNOT rely on similarity of DNA to determine whether contemporary humans descended from a particular group (since we KNOW that contemporary humans descended from their PHS ancestors).

This would nullify the author's evidence, so choice (C) is the best answer.

I hope this helps!

therick79 · Answer

I don't know what is technically the right answer, but I'd have to pick A. That seems to me to fit the best.

Sent from my iPhone using GMAT Club Forum

akshayk · Answer

Old Belief - Prehistoric homesapinen ancestors of contemporary humans interbred with Neanderthals.
Contradiction - DNA testing of Neanderthal remains indicates this is NOT the case.
Result - DNA of contemporary humans is SIGNIFICANTLY different from that of N's.

Which one of the following is an assumption required by the anthropologist’s argument?
 
The argument is about the similarity or lack thereof of the DNA, so this is irrelevant. OUT!

This is a far-fetched assumption that LSAT has made for us, but the argument in no shape or form refers to this idea. OUT!

If pre-historic homosapien's interbred with neanderthals, then the author would have to assume that the contemporary human's DNA has not evolved at all to showcase similarity. And is further proven as the researcher test the DNA of contemporary humans with neanderthals. This is a good option. KEEP!

Contradicts the old belief i.e. the premise so this is OUT!

Let's say this is true, but we did not find any overlap in the DNA. Does that mean they did not interbreed especially when we have not compared the DNA of prehistoric homosapiens with neanderthals. Close, but C is better. This is OUT too!

C is the right answer.

saurabhSuman · Answer

from what I understand in choice C is Unlike DNA of Homo Sapiens, DNA of contemporary humans are much more closer to Neanderthals.
but the argument says otherwise "The DNA of contemporary humans is significantly different from that of the Neanderthal."
 akshayk 
Can you please elaborate on what you mean by "evolving to showcase similarity" in these lines 
"If pre-historic homosapien's interbred with neanderthals, then the author would have to assume that the contemporary human's DNA has not evolved at all to showcase similarity. And is further proven as the researcher test the DNA of contemporary humans with neanderthals. This is a good option. KEEP!
"

arvind910619 · Answer

Hi mikemcgarry

I chose E but that is not the answer .
C is the answer .
I chose option E because it says similarity in DNA is caused by interbreeding than the DNAs are different and that is why the conclusion follows.
Regarding C I did not understood it in the first place but I'm more close reading it says that the DNA of ancestors is not more similar to the DNA of the Neanderthal than the DNA of the modern human beings .
Please help me in my reasoning and what is rationale for C to be the correct answer

gmatexam439 · Answer

abhimahna 
Please explain option C and E. Why is C correct and E wrong?
The conclusion of the argument is that "the ancestors didn't breed with neanderthals". I think E correctly shows that.

Regards

abhimahna · Answer

Hi  gmatexam439  ,

Here is the catch. We are told that since their DNAs donot match, they didn't interbreed.

Note that we cannot NEVER assume that if they match they MUST interbreed.

This is a common mistake that we all do.

Take the following example:

If I am an Indian IT Male, I cannot get into Harvard.

Now, if you say the following, it would be 100% incorrect.

If I am not an Indian IT Make, I must get into Harvard. Really?? What if I am chinese?

So, be extremely careful about such situations.

C is correctly saying that DNA doesn't change in time, meaning my current DNAs are similar to the DNAs of my ex-ex-ex-ex-ex grand parent.

Does that make sense?

arvind910619 · Answer

Hi mikemcgarry

I chose E but that is not the answer .
C is the answer .
I chose option E because it says similarity in DNA is caused by interbreeding than the DNAs are different and that is why the conclusion follows.
Regarding C I did not understood it in the first place but I'm more close reading it says that the DNA of ancestors is not more similar to the DNA of the Neanderthal than the DNA of the modern human beings .
Please help me in my reasoning and what is rationale for C to be the correct answer

subrataroy0210 · Answer

Anthropologist: It was formerly believed that prehistoric Homo sapiens ancestors of contemporary humans interbred with Neanderthals, but DNA testing of a Neanderthal’s remains indicates that this is not the case. The DNA of contemporary humans is significantly different from that of the Neanderthal.
 
Conclusion: Since DNA of contemporary humans is significantly different from that of the Neanderthal, the prehistoric Homo sapiens ancestors of contemporary humans did not interbreed with Neanderthals.

Falsification Situation: 
1) What if the remains only give partial information about the DNA of the Neanderthals?
2) It is not necessary that when A and B breed, the offspring C will have the DNA traces of both A and B in a significant amount.

Possible assumptions:
1) DNA does not destroy with time and thus the remains do not provide any partial information.
2) The offspring has DNA traces of both the parents in significant proportion.

Which one of the following is an assumption required by the anthropologist’s argument?

(A) At least some Neanderthals lived at the same time and in the same places as prehistoric Homo sapiens ancestors of contemporary humans.
 Negate: No Neanderthals lived at the same time and in the same places as prehistoric Homo sapiens ancestors of contemporary humans.
This rather supports the fact that prehistoric Homo sapiens and Neanderthals did not breed; they never got a chance.
 
(B) DNA testing of remains is significantly less reliable than DNA testing of samples from living species.
 Negate: DNA testing of remains is significantly reliable than DNA testing of samples from living species.
This means that the DNA testing of the remains is reliable and thus the conclusion is okay.

(C) The DNA of prehistoric Homo sapiens ancestors of contemporary humans was not significantly more similar to that of Neanderthals than is the DNA of contemporary humans.
 Negate: The DNA of PHS ancestors of contemporary humans was significantly more similar to that of Neanderthals than is the DNA of contemporary humans.
This information tells us that the PHS is not the ancestors of contemporary human as the DNA will not match. This information destroys the conclusion from within because it makes us believe that the DNA-testing is faulty. This option is a possible conclusion. 
 
(D) Neanderthals and prehistoric Homo sapiens ancestors of contemporary humans were completely isolated from each other geographically.
 Negate: Neanderthals and prehistoric Homo sapiens ancestors of contemporary humans were not completely isolated from each other geographically.
This does not affect the conclusion.

(E) Any similarity in the DNA of two species must be the result of interbreeding.
 Negate: No similarity in the DNA of two species must be the result of interbreeding.
As per the argument, the DNA of contemporary humans and the DNA of the remains of Neanderthals are significantly different but we cannot say that there is no similarity between them. Thus, this information does not affect the conclusion.

gmatexam439 · Answer

Hi @abhimanha Bro,

The DNA of  prehistoric Homo sapiens ancestors  (father) of  contemporary humans  (child) was not significantly more similar to that of  Neanderthals  (step mom) than is the DNA of  contemporary humans  (child).

This argument is basically saying father's dna wasn't similar to step-mom's dna. father's dna was similar to dna of child.

So we are basically stating that dna of father and child are same that's why they are ancestors and successors. but the same is not the case with step-mom and child.

Is my understanding of the statement correct?

Regards

arvind910619 · Answer

Hi GMATNinja ,

Thanks for the wonderful explanation.

Regards,
Arvind

Kritisood · Answer

I was down to C and E because of POE, but didnt really understand C, hence chose E. After reading C 5 plus times, i still cant understand how it proves that contemporary humans DNA hasnt evolved at all to showcase similarity. Please help.

CrackverbalGMAT · Answer

One good reason to eliminate option E is the fact that E is a blanket statement of sorts ("any two species") and is extreme. Look at the keywords "any similarity" and "must be".

Now, let's look at Option C: 
(C) The DNA of prehistoric Homo sapiens ancestors of contemporary humans was not significantly more similar to that of Neanderthals than is the DNA of contemporary humans.

One of the reasons why C is overlooked is the convoluted language. Once you disentangle the reasoning, it will be easy to see why it is the right answer.

Let’s try paraphrasing option C – 
The DNA of the PH ancestors was more similar to the DNA of contemporary humans than it was similar to the Neanderthals. This means that the contemporary human’s DNA was not evolved at all—only then would it be significantly more similar to that of the Homo sapiens (ancestors). Does that help?

Yellkrishna · Answer

The conclusion is that the ancestors of humans did not interbreed with Neanderthals.

The reason stated is that the DNA of Neanderthals is significantly different from DNA of humans.

A. While this statement is necessary for the above premise to happen, the conclusion is not dependent on it.

B. This is out of scope.

C. This is a good option. If the DNA of human ancestors is closer to that of the Neanderthals, them the argument fails. Lets keep it.

D. This is out of scope.

E. If the stimulus would have said that the Neanderthal DNA was ‘completely different’ from human DNA instead of ‘significantly different’ then this argument would have held. But now as such, significantly different means that there are some similarities between the two DNAs. Hence, this argument does not hold.

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ngochuyen1904 · Answer

Premise:    
The DNA of contemporary humans is significantly different from that of the Neanderthal

Conclusion:    
Prehistoric Homo sapiens ancestors of contemporary humans interbred with Neanderthals

Pre-think:    
In order to analyze this argument, we have to assume another thing is that If Homo sapiens are ancestors of contemporary humans, then the DNA of contemporary humans has at least some similarity with DNA of Homo sapiens

So, what if DNA of contemporary humans has more similarity with that of Neanderthal than with that of Homo sapiens?
Now, our conclusion collapses. Since how come contemporary humans whose DNA has more similarity with DNA of Neanderthal but contemporary humans are descendants of Homo sapiens, not of Neanderthal? It’s illogical

That’s exactly what  option C  is saying

Dooperman · Answer

Clearly C vs E.

We know "The DNA of contemporary humans is significantly different from that of the Neanderthal." What if the prehistoric humans did interbreed with the Ns and the resulting DNA had a similarity with that of the Ns. C helps us reject this doubt that the DNA of earlier humans was also not similar to the Neanderthals.

E says "ANY" similarity has to come from interbreeding.
We know that The DNA of contemporary humans is "SIGNIFICANTLY DIFFERENT" (say 95% or 99%) from that of the Neanderthal.
This suggests that there is "SOME" similarity (say 1%) between the DNAs. If E were true, it would mean that this little similarity has resulted from the interbreeding (which is opposite to what is stated in the passage that there was NO interbreeding)

Raman109 · Answer

Understanding the argument - 
Anthropologist: It was formerly believed that prehistoric Homo sapiens ancestors of contemporary humans interbred with Neanderthals, but DNA testing of a Neanderthal’s remains indicates that this is not the case. - Conclusion "The prehistoric Homo sapiens and Neanderthals did not interbred."

The DNA of contemporary humans is significantly different from that of the Neanderthal. - Fact

Which one of the following is an assumption required by the anthropologist’s argument?

(A) At least some Neanderthals lived at the same time and in the same places as prehistoric Homo sapiens ancestors of contemporary humans. - Strengthener but not an assumption. Negation says they did not live in the same time and place, but they still could have interbred. It's about genetics and not about time and location.

(B) DNA testing of remains is significantly less reliable than DNA testing of samples from living species. - reliability is out of scope.

(C) The DNA of prehistoric Homo sapiens ancestors of contemporary humans was not significantly more similar to that of Neanderthals than is the DNA of contemporary humans. - negation means they were similar, meaning they interbred. The current differences can be caused by other factors, such as mutations.

(D) Neanderthals and prehistoric Homo sapiens ancestors of contemporary humans were completely isolated from each other geographically. - Weakener, at best, though the argument is about genetics, and they could still have interbred, and is not about location.

(E) Any similarity in the DNA of two species must be the result of interbreeding. - The anthropologist's argument does not depend on this claim. Similar DNA could result from common ancestry or other evolutionary factors, not just interbreeding. This assumption is not required for the argument to hold.

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Anthropologist: It was formerly believed that prehistoric Homo sapiens

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