According to the traditional hypothesis, the first humans to inhabit

Question

According to the traditional hypothesis, the first humans to inhabit North America came across a land bridge between northeast Asia and Alaska approximately 12,000 years ago. But a group of archaeologists now theorizes that some humans arrived in Baja California approximately 13,500 years ago. This hypothesis must be false, however, because the oldest human fossil remains that have been found in North America are only 12,000 years old.

The argument above assumes that:

A. There will be no new archaeological discoveries in North America that disprove conventional theories.
B. The land bridge used by humans 12,000 years ago was not in existence 13,500 years ago.
C. There have not been discoveries of fossilized human tools from more than 13,000 years ago made in North America.
D. Archaeologists have an incentive to make up incorrect theories regarding early human migration.
E. Human beings did not have a way to reach North America prior to the formation of the land bridge known to have been used by people 12,000 years ago.

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bidita · Answer

So the basis behind the author making the conclusion is that 'the oldest human fossil remains that have been found in North America are only 12,000 years old' and hence 'the first human to inhabit NA was approximately 12,000 years ago'.

Now try negating answer choice C: There  have been  discoveries of fossilized human tools from more than 13,000 years ago made in North America. Wouldn't that mean that some humans indeed arrived in NA 13,500 years ago? 
Therefore, negating C will make the argument fall apart.

Bunuel · Answer

VERITAS PREP OFFICIAL SOLUTION:

Like many assumption problems, this problem features an argument with a broad conclusion ("this hypothesis must be false") hanging precariously on one premise (essentially "there are no human fossil remains to support that hypothesis"). A helpful thing to keep in mind on assumption questions - and a reason that the Assumption Negation Technique can be so helpful - is that often the correct answer is necessary to keep the lone existing premise relevant.

Here's how that works on this problem: the lone premise is very specifically worded to include "no human fossil remains." But are human fossil remains the only type of evidence that could indicate or prove human existence?

When choice C is negated, it provides that other type of evidence: "there HAVE been discoveries of fossilized human tools" that date back well before the established theory's timeframe. If this were true, then those purveying the new theory would have evidence for it, thereby directly weakening this argument.  Choice C therefore is correct . And note again its structural function - as it reads pre-negation, it helps to protect the current premise (there are no human fossils that support the new theory) from becoming irrelevant.

Choice A is too broad: there may very well be future discoveries that disprove some current theories, but that doesn't necessarily mean that they will disprove the current prevailing theory about when people arrived in North America. Even if that theory is ultimately disproven, too, that doesn't mean it will be replaced with the proposed new theory.

Choice B fails the negation test: if you negate B, you'll see that the land bridge WAS in existence 13,500 years ago. But is that evidence that people were there, particularly in light of the existing premise that there is no fossil evidence from that 1,500 year period?

Choice D similarly is unnecessary: it doesn't have to be that the archaeologists lied, as they could just be wrong. If you negate it and it then says "archaeologists do not have a reason to make up incorrect theories" the argument could still hold - they'd be wrong and maybe even bad scientists, just not liars.

Choice E also fails the negation test: if you negate it, it actually gives a little more hope to the new theory by saying that people DID have a way to get to North America even without the land bridge. That certainly doesn't prove the case, but it leaves the door open even a bit further that the new theory could be correct.

vasu1104 · Answer

conclusion- this hypothesis must be false. 
 reason- oldest human fossils remains are only 12000 years old. 
 So they are rejecting one hypothesis based on the fact that human remains was 12000 old but what if its been sitting there before that but they found the tools to evaluate after it?

options A,B, D are easy to eliminate. 
 E talks about not having any other way to enter but that doesnt break the cocnlusion. 
 C it must be assumed. if there were tools before 13000 then conclusion breaks down because we can accurately figure out. so they are assuming that there was nothing apart from human fossils to make their conclusion.

egmat · Answer

Your Logic:  "If archaeologists can't make mistakes (negating D), their theory must be true, so the argument falls apart."

The Problem:  You're mixing up two different things:
 1.  Having no bad motive (what D talks about)
 2.  Being factually correct

Think of it this way:  I could be the most honest, well-intentioned person with zero incentive to lie... and still be  WRONG  about something.

Honesty ≠ Accuracy

The argument author isn't attacking the archaeologists' character or motives. They're saying: "Your theory is wrong because the  EVIDENCE  doesn't support it (only  12,000 -year-old fossils found)."

Why C is the Answer:

The argument's core logic is: "Oldest fossils found =  12,000  years →  Therefore , no humans before  12,000  years."

This  assumes  we haven't found  ANY  evidence of earlier humans - not just bones, but  tools  too.

Negation Test for C: 
• Negate it: "Fossilized human tools from  13,500  years ago  HAVE  been found"
• Result:  The argument completely falls apart!  You can't claim "no evidence of earlier humans" if we found their tools.

Negation Test for D: 
• Negate it: "Archaeologists have NO incentive to make up theories"
• Result: So what? The argument is about  evidence , not motives. The argument still stands.

Where you went wrong:  Option D is about  motive/character , but the argument is built on  physical evidence . Even if archaeologists are perfectly honest (no bad incentives), that doesn't make their specific theory true or false - only evidence can do that.

agrasan · Answer

Hi  KarishmaB   MartyMurray   IanStewart

E. Human beings did not have a way to reach North America prior to the formation of the land bridge known to have been used by people 12,000 years ago.

I understand how (C) is correct but unable to reject (E).  My reasoning is:  If there was a way to reach NA prior to the bridge formation 12000 yrs ago then how the author can conclude that humans didn't arrive in California 13,500 yrs ago, in that case we cannot believe in author's conclusion  "hypothesis must be false" , thus, (E) has to be an assumption.

Please let me know where I am going wrong.

miag · Answer

Hi, Let me try to help out with this one: The issue with (E) is that the argument never relies on how humans reached North America. It relies only on the absence of fossil evidence older than 12,000 years. Even if there were a way for humans to reach North America before the land bridge (negating E), the author could still conclude the hypothesis is false by saying: "If humans were here 13,500 years ago, we would have found older fossils." Therefore, (E) is not required for the argument to work. Hope this helps!

ParamjitDasGMAT · Answer

Hi,
Although the question isn’t addressed to me, I’ll try to help out with (E).

Even if humans had a way to reach North America prior to 12k years ago, it doesn’t mean that they used the way. The argument/conclusion is about whether humans arrived 12k/13.5k years ago.

Hence, the assumption - what is the statement that the author takes as true in his mind of minds when going from the premise to the conclusion - of the author wouldn’t be that people didn’t *have a way* to reach that location. It would be more along the lines of whether the reported evidence is accurate or that no additional evidence -the argument is also about the evidence *collected to date*- will prove that humans arrived 13.5k years ago.

Hope it helps.

Let me know if anything is unclear.

agrasan · Answer

Thanks  ParamjitDasGMAT

If I follow you, the author says   "  This hypothesis must be false, however, because the oldest human fossil remains that have been found in North America are only 12,000 years old."    which is in the form    Since X, therefore Y,    so we have to find an assumption which bridges the gap between X and Y right? Is this why the bridge or an alternative route not a concern for us?

ParamjitDasGMAT · Answer

Not quite. Had option (E) stated “there is no alternative evidence which needs to be reviewed before we can conclude humans didn’t arrive 13.5k years ago”, it would have been correct. This is, in fact, similar to what (C) says.

My point was that *having a way to do something* doesn’t mean that something was done. This is a common type of flaw in a CR arg - planning to do X vs actually doing X.

Here the focus would be on the actual arrival date, not whether some mechanism existed for them to arrive.

Hope this helps.

agrasan · Answer

Thanks, much helpful, am clear now.

According to the traditional hypothesis, the first humans to inhabit

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According to the traditional hypothesis, the first humans to inhabit

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