Most archaeologists have held that people first reached the Americas

Most archaeologists have held that people first reached the Americas less than 20,000 years ago by crossing a land bridge into North America. But recent discoveries of human shelters in South America dating from 32,000 years ago have led researchers to speculate that people arrived in South America first, after voyaging across the Pacific, and then spread northward.

Speculation is that people first entered south america and then moved to north America. We have to find any evidence which is against the above conclusion.

A. A rock shelter near Pittsburgh, Pennsylvania, contains evidence of use by human beings 19,000 years ago. .Humane were there 19000 years ago no effect on conclusion

B. Some North American sites of human habitation predate any sites found in South America.means people might have come to north america first...

C. The climate is warmer at the 32,000-year-old South American site than at the oldestknown North American site. more chance people moved to south america first

D. The site in South America that was occupied 32,000 years ago was continuously occupied until 6,000 years ago. no info about north amrica

E. The last Ice Age, between 11,500 and 20,000 years ago, considerably lowered worldwidesea level . out of scope

The actual premise says, "Most archaeologists have held that people first reached the Americas less than 20,000 years ago by crossing a land bridge into North America." This is followed by the word "but"...THIS IS A CLASSIC SETUP ON THE GMAT. The author of the stimulus is not saying that the migration happened less than 20 thousand years ago. He or she is saying that someone (in this case archaeologists) believe it. With the word "but" we have a negation and we see that the author of the stimulus does not take the belief as a fact and is indeed contradicting it immediately. ­

Conclusion: [recent discoveries of human shelters in SA dating from 32k years ago have led] researcher [to] speculate that people arrived in SA 1st, AFTER voyaging across the Pacific, and THEN spread northward
Prethink: What if it’s the opposite? What if they inhabited NA and went down to SA?
Which of the following, if it were discovered, would be pertinent evidence against the speculation above?

(A) A rock shelter near Pittsburgh, Pennsylvania, contains evidence of use by human beings 19,000 years ago.
This is a neutral trap – the conclusion could still very well be true. What if people arrived at SA 32k years before THEN moved upward to NA (particularly Pittsburgh, PA) by the 19k year mark. It’s a trap because this number is fairly close to the 20k number within the first sentence. The test makers want you to choose this because of that reason. But if you really think about it, it has no real impact and doesn’t cast doubt on the conclusion.

(B) Some North American sites of human habitation predate any sites found in South America.
Reversal: This shows that instead of SA -> NA, it was NA -> SA, weakening the conclusion.

(C) The climate is warmer at the 32,000-year-old South American site than at the oldest known North American site.
Out of scope – climate is completely irrelevant.

(D) The site in South America that was occupied 32,000 years ago was continuously occupied until 6,000 years ago.
Potentially, opposite. If it was occupied for so long, wouldn’t one think that they would eventually venture out, eventually landing up north? This is kind of big stretch, but at worst, this does nothing to the conclusion.

(E) The last Ice Age, between 11,500 and 20,000 years ago, considerably lowered worldwide sea levels
Out of scope/story trap. We have that the rough ball park number that’s within the first sentence. This doesn’t change anything still. It’s very much possible that people still arrived in SA first, then moved up north, regardless of when the last ice age occurred.

Hello experts,
I went through the answers and post given by many people for this question but can you please help me understand what exactly option B is saying and why it is the correct answer and not option D because Option D does provide the evidence that people were there 32,000 years back so they must have traveled to North America. Please correct me if I applying the wrong logic over here.

(D) doesn't really change much. The fact that people were at that site in South America from 32,000 years ago to 6,000 years ago does not mean they traveled to North America. They could have just remained near that one site.

The question ask us "Which of the following, if it were discovered ...?"

So, this question is confusing, because it asks us not about a fact that is already known to be true, but about the effect of a new fact, one that has not been discovered yet.

If we keep in mind what the question is asking, then that (B) is correct becomes pretty clear.

Here's (B).

(B) Some North American sites of human habitation predate any sites found in South America.

Notice, this is a NEW discovery, one that has not been taken into account by the archeologists who have held that people first reached the Americas less than 20,000 years ago.

This new discovery would indicate that, even before people were at that 32,000 year old site in South America, people were in North America.

Of course, such a new discovery would be evidence against the speculation that people arrived in South America first, after voyaging across the Pacific, and then spread northward.

By eliminating all incorrect options, I was able to choose the correct option. I am even convinced that the correct option is B because it tell us that people must have reached NA first as we have sites inhabited by human that predate any sites inhabited by human in SA (i.e 32,000 years old)

Can someone please explain how can the researchers opined that the people first reached NA less than 20,000 years ago when they could find sites older than 32,000 years?

sidharthbanda1
Sadly, in real life, many people hold positions that are contradicted by the available evidence. But in this case, no such failure of logic is required. Note the timing: archaeologists have held that people came to NA less than 20,000 years ago, but now recent finds show that this may not be as likely. Presumably, many of them will now change their position.

Most archaeologists have held that people first reached the Americas less than 20,000 years ago by crossing a land bridge into North America. But recent discoveries of human shelters in South America dating from 32,000 years ago have led researchers to speculate that people arrived in South America first, after voyaging across the Pacific, and then spread northward.

Which of the following, if it were discovered, would be pertinent evidence against the speculation above?


(A) A rock shelter near Pittsburgh, Pennsylvania, contains evidence of use by human beings 19,000 years ago. X

OK, but this doesn’t weaken the conclusion. What we need to show is that people settled in the Americas BEFORE they settled in South America. This has to have occurred more than 32,000 years ago.

(B) Some North American sites of human habitation predate any sites found in South America.

Correct. Key word here is ‘predate’. This is exactly what we need to weaken the idea that people arrived in SA first.

(C) The climate is warmer at the 32,000-year-old South American site than at the oldest known North American site. X

“Climate” is irrelevant

(D) The site in South America that was occupied 32,000 years ago was continuously occupied until 6,000 years ago. X

OK, but this does nothing to weaken the main conclusion

(E) The last Ice Age, between 11,500 and 20,000 years ago, considerably lowered worldwide sea levels X

“Sea levels” is irrelevant

The speculation presented suggests that people arrived in South America first and then spread northward. To weaken this speculation, we need to find evidence that supports the traditional belief that people first reached the Americas via a land bridge into North America. Let's evaluate each option:

(A) A rock shelter near Pittsburgh, Pennsylvania, contains evidence of use by human beings 19,000 years ago.
This option supports the traditional belief that people reached North America first, as it provides evidence of human habitation in North America around 19,000 years ago. It does not directly address the arrival in South America.

(B) Some North American sites of human habitation predate any sites found in South America.
This option further supports the traditional belief by indicating that human habitation in North America predates any known sites in South America. It suggests that people were present in North America before South America.

(C) The climate is warmer at the 32,000-year-old South American site than at the oldest known North American site.
The climate difference does not directly address the issue of the initial arrival of people in the Americas or the sequence of their migration. It is not pertinent evidence against the speculation.

(D) The site in South America that was occupied 32,000 years ago was continuously occupied until 6,000 years ago.
This option supports the possibility of long-term occupation in South America but does not provide evidence against the speculation of people arriving in South America first. It does not address the initial migration or the spread northward.

(E) The last Ice Age, between 11,500 and 20,000 years ago, considerably lowered worldwide sea levels.
While this information is relevant to the history of sea levels during the last Ice Age, it does not directly address the speculation or provide evidence against it.

Based on the analysis, the option that provides pertinent evidence against the speculation is (B) Some North American sites of human habitation predate any sites found in South America. This evidence supports the traditional belief that people reached North America first, suggesting that the migration to South America occurred after the initial arrival in North America.