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Researchers have long noted strange grooves near the gum lines on 13 Jul 2025, 07:54
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MartyMurray Could you please tell me how option e) strengthens the hypothesis, for evaluating questions we need to weaken and strengthen both right?
MartyMurray
The anthropologist's hypothesis is the following:

the early humans used grass stalks [for tooth picking]

The support for that hypothesis is the following:

[The grass stalks] unlike wood, contain abrasive silica, a substance that would facilitate the development of the grooves

The correct answer must be "useful to the evaluation of the anthropologist's hypothesis."

Since the answer choices are statements, the correct answer will simply weaken or strengthen the argument.

A. The dental remains that have the type of grooves in question almost as commonly show signs of tooth decay as do the remains that lack the grooves.

This choice has no effect on the argument. The fact that the dental remains show signs of tooth decay does not indicate anything about what caused the grooves or whether the early humans used grass stalks for tooth picking. After all, dental decay could occur regardless of whether they did or didn't use grass stalks for tooth picking.

Eliminate.

B. Dental remains of some of the early humans without the grooves have been found at places where the available grass could have been suitable for tooth picking during their lifetimes.

The fact that grass suitable for tooth picking may have existed where early humans' teeth did not have the grooves doesn't tell us whether the grooves were caused by use of grass for cleaning teeth. After all, it's not the case that all early humans must have used the available resources in the same way. It's likely that some early humans didn't use grass to clean their teeth.

Eliminate.

C. Unlike grass stalks, few modern-day toothpicks contain significant amounts of abrasive silica.

This information has already been provided by the passage. The passage indicates that grass stalks are "unlike" modern toothpicks in that grass stalks contain silica. Information already provided cannot have any new effect on the argument.

Eliminate.

D. Abrasive silica derived from grasses and other, similar plants could be useful in the removal of cavity-causing plaque from humans' teeth.

This choice has no effect on the argument. The fact that abrasive silica derived from grasses and other, similar plants could be useful in the removal of cavity-causing plaque doesn't mean that early humans used abrasive silica or grass stalks containing abrasive silica to clean their teeth.

Eliminate.

E. The grooves occur on the teeth of some early humans whose remains were found at places where no grass suitable for tooth picking would have been obtainable during their lifetimes.

This choice weakens the argument. We see that the effect "grooves occur on the teeth" exists where the presumed cause "grass suitable for tooth picking" did not exist. This information indicates that the use of grass for tooth picking was not the cause of the grooves since the grooves appear to have occurred even without the grass.

The correct answer is
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Researchers have long noted strange grooves near the gum lines on 14 Jul 2025, 05:40
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MartyMurray Could you please tell me how option e) strengthens the hypothesis, for evaluating questions we need to weaken and strengthen both right?
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Actually, the correct answer to an Evaluate question does not have to both strengthen and weaken.

In most Evaluate questions in which the answers are questions, different answers to the correct answer question do strengthen and weaken. At the same time, an answer to the correct answer question has to do only one or the other for that answer to be correct. In other words, if an answer to the question posed by a choice either weakens or strengthens, then that choice is correct.

Meanwhile, in this question, the answers are not questions - they are statements - and a statement can only weaken or strengthen. So, the correct answer, (E), only weakens the case for the conclusion.
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Researchers have long noted strange grooves near the gum lines on 15 Jul 2025, 07:55
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soumyab12
Thank you for the explanation, but isn't E irrelevant if we think about mobility of early humans? Just because grass of the area where remains were found isn't suitable, doesn't mean that early humans in their lifetime did not travel and habitate in areas where grass suitable for tooth picking is found? As per my understanding, it is pretty much okay to assume that these early humans used to move around a lot.

It would be really helpful if you could clarify, thank you.
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(E) says that the "remains were found at places where no grass suitable for tooth picking would have been obtainable during [the early humans'] lifetimes."

If the early humans living in those places were able to move around to obtain the grass, then (E) would not be true because, in that case, the grass WOULD have been obtainable.

(E) says that the early humans living in those places would NOT have been able to OBTAIN the grass during their lifetimes, so that excludes the possibility of moving around and obtaining the grass elsewhere.
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Researchers have long noted strange grooves near the gum lines on 27 Jul 2025, 03:05
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a little confused about option (E) and would love some insights and help.
" E. The grooves occur on the teeth of some early humans whose remains were found at places where no grass suitable for tooth picking would have been obtainable during their lifetimes."

--> is it not possible that 'some' of these humans who might have picked their teeth with grass all their lives just died or had their remains found away from their homes? may be they travelled or their civilisation was destroyed in a flood etc.? "Some" does not tell that this group of people was sizeable so I'm confused how a one-off finding can significantly weaken the correlation the anthropologist is trying to draw.

Your help is appreciated, please do correct my reasoning!
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Researchers have long noted strange grooves near the gum lines on 10 Aug 2025, 05:25
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anushkatew
a little confused about option (E) and would love some insights and help.
" E. The grooves occur on the teeth of some early humans whose remains were found at places where no grass suitable for tooth picking would have been obtainable during their lifetimes."

--> is it not possible that 'some' of these humans who might have picked their teeth with grass all their lives just died or had their remains found away from their homes? may be they travelled or their civilisation was destroyed in a flood etc.? "Some" does not tell that this group of people was sizeable so I'm confused how a one-off finding can significantly weaken the correlation the anthropologist is trying to draw.

Your help is appreciated, please do correct my reasoning!
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Remember: weakening a conclusion isn't the same as obliterating it. It just has to be less likely.

Imagine that you're investigating a murder. You have a suspect in mind. Let's suppose that his name is Tim.

In the course of your investigation, you learn that the murder weapon was acquired in New Hampshire on a day when Tim was in Spain. Can you be 100% certain that Tim is innocent? Nope. Maybe someone else bought the weapon and gave it to Tim!

But should this knowledge weaken your confidence in Tim's guilt? Yeah. Seems more likely that the actual perpetrator bought the weapon while Tim was eating tapas and taking four-hour siestas.

Similar reasoning here. If the bodies of these early humans were found in places where the grass "would not have been obtainable in their lifetimes," it makes it seem less likely that they were using this unavailable grass to pick their teeth, right?

Is it theoretically possible that these proto-people traveled to places where the grass was obtainable, picked their teeth, and then traveled back to the grass-free location where they were subsequently gored by tigers? I guess. But I'm definitely less confident in the original grass-tooth-picking hypothesis. And that's good enough to qualify as a weakener.

The takeaway: a good weakener doesn't have to be bulletproof. It just has to make the conclusion less likely to be true.

I hope that helps!
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Researchers have long noted strange grooves near the gum lines on 13 Aug 2025, 15:34
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Hi, I found this question to be unusual or at least very different from the rest of the evaluate question..because generally...we get....choices like..whether there was xxxxx ..Which gives us the possibility to do the Yes/No test or as some call it the extreme test...

Here, its different. I get Option B is strengthening, but is Option E not weakening the argument?.....Also, how do we do the extreme test, because the question stem says..if true...so we have to consider it true.....
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GMATNinja - Can you please help in explaining option choice B and E. For me grass stalks caused the grooves in the early humans.

B. Dental remains of some of the early humans without the grooves have been found at places where the available grass could have been suitable for tooth picking during their lifetimes.

From B option choice are we interpreting that those people could have used tooth picking but they didnt use and hence no grooves? Hence, this is acting as a strengthener?­
(­B) is only a strengthener if we assume that the anthropologist is correct. In that case, the absence of grooves would suggest an absence of tooth picking.

But what if the anthropologist is wrong? In that case, the grooves could be present with or without tooth picking. And since the humans described in (B) COULD have engaged in tooth picking, their lack of grooves might actually work against the anthropologist's hypothesis -- it's evidence that you can have tooth picking without grooves.

Without additional information, (B) doesn't strengthen or weaken the hypothesis -- it could go either way.

(E), on the other hand, gives us an example of having grooves in a place where tooth picking with grass stalks would NOT have been possible. That means that the grooves MUST have been caused by something else besides tooth picking.

That's strong evidence that the anthropologist's hypothesis is incorrect and thus very useful in evaluating the argument (note that "evaluating" and "strengthening" are not the same thing).

I hope that helps!­
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Researchers have long noted strange grooves near the gum lines on 17 Aug 2025, 17:12
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Aboyhasnoname
Hi, I found this question to be unusual or at least very different from the rest of the evaluate question..because generally...we get....choices like..whether there was xxxxx ..Which gives us the possibility to do the Yes/No test or as some call it the extreme test...

Here, its different. I get Option B is strengthening, but is Option E not weakening the argument?.....Also, how do we do the extreme test, because the question stem says..if true...so we have to consider it true.....
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You're right, the wording of this question is different and important.

Often with "evaluate" questions, your job is to ask yourself, "Would knowing the answer to the question posed in this answer choice help me evaluate the hypothesis?"

But in this case, you have to ask yourself, "If this answer choice is true, would that help me evaluate the argument?". It's an entirely different question, and that's why the so-called "extremes test" does not apply.

If (E) is true, then we have strong evidence that the anthropologist's hypothesis is incorrect. So knowing that (E) is true absolutely helps us to evaluate the hypothesis (our evaluation, based on (E), is that the hypothesis is incorrect). Meanwhile, knowing that (B) is true does not necessarily strengthen the argument.

For more on that, check out these posts from earlier in the thread:


  1. https://gmatclub.com/forum/researchers-have-long-noted-strange-grooves-near-the-gum-lines-on-417070.html#p3401098
  2. https://gmatclub.com/forum/researchers-have-long-noted-strange-grooves-near-the-gum-lines-on-417070-20.html#p3603559
  3. https://gmatclub.com/forum/researchers-have-long-noted-strange-grooves-near-the-gum-lines-on-417070-20.html#p3614718

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