Researchers have long noted strange grooves near the gum lines on

Question

﻿Researchers have long noted strange grooves near the gum lines on dental remains of some early humans. The marks are absent from the teeth of modern-day toothpick users, and have therefore been assumed not to present evidence of tooth picking where they have been present. But an anthropologist has recently proposed that the early humans used grass stalks, which, unlike wood, contain abrasive silica, a substance that would facilitate the development of the grooves.

Which of the following would, if found to be true, be most useful to the evaluation of the anthropologist's hypothesis?

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.

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.

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

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

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.

MartyMurray · Accepted Answer

The anthropologist's hypothesis is the following:

the early humans used grass stalks

The support for that hypothesis is the following:

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  E

Paras96 · Answer

The hypothesis being evaluated is that early humans used grass stalks to create grooves on dental remains.  Option E  is crucial because it directly challenges the hypothesis. If grooves occur on the teeth of early humans whose remains were found in places where no suitable grass for tooth picking was available, then it weakens the idea that these grooves were a result of using grass stalks. This information would suggest that some other factor might be causing the grooves, thus making the anthropologist's hypothesis less convincing.

GmatKnightTutor · Answer

﻿Researchers have long noted strange grooves near the gum lines on dental remains of some early humans. The marks are absent from the teeth of modern-day toothpick users, and have therefore been assumed not to present evidence of tooth picking where they have been present. But an anthropologist has recently proposed that the early humans used grass stalks, which, unlike wood, contain abrasive silica, a substance that would facilitate the development of the grooves.

Which of the following would, if found to be true, be most useful to the evaluation of the anthropologist's hypothesis?

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.

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.

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

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

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.

The passage talks about certain gum marks found in early humans but not in humans today who do tooth picking. Although this may suggest early humans did not do tooth picking, an anthropologist's theory is that this could be because early humans used grass stalks. The idea being that grass stalks have an abrasive substance (unlike wood) that would help cause these marks.

We're asked to look for something that would help in evaluating the anthropologist's theory

(E) is the answer. If early humans - in an area where there is no grass for tooth picking STILL had these gum marks - it would mean something ELSE was the cause.

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jaky_nguyen · Answer

Hi  MartyMurray ,

Would you think if the information in B is not true, it will weaken the argument? Thanks

MartyMurray · Answer

Here's (B).

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.

Here's the negation of (B).

B.  No dental remains of early humans without the grooves have been found  at places where the available grass could have been suitable for tooth picking during their lifetimes.

If anything, that negated version of (B) would strengthen the argument a little, by showing that, wherever grass that could have been suitable for tooth picking existed, early humans had the grooves and that, wherever dental remains without the grooves were found, there hadn't been grass that could have been suitable for tooth picking. That information would indicate that the grass was connected to the grooves in teeth and thus to tooth picking.

Aarushi0505 · Answer

Hi,

For option B, in the question prompt it has been mentioned that grass stalks contain silica, however, in option B it has been mentioned that toothpicks contain silica but in the explanation for option B it's eliminated by stating that the information is already present in the prompt. I am a bit confused regarding this option. Can someone please explain.

Thanks.

tribui · Answer

MartyMurray , I would think that for an "evaluate" question, the answer choice does not have to strongly prove or disprove the conclusion, so in this case it only needs to affect ie. strengthen or weaken the hypothesis.
For B: - if that info is true, it would weaken the hypothesis a little since there's remains without grooves where there's grass available, so maybe the grass does not cause the grooves. Again, there could be many other factors, but all else being the same, shouldn't it weaken the hypothesis?
- If the info is false ie. negation, that would strengthen the hypothesis a little, as you already explained.

I can see the same pattern for E. So in this case I'm struggling to see why E is better than B at all. Can someone help?

MartyMurray · Answer

Notice that the conclusion of the argument is about the cause of the grooves in teeth in which the grooves are present. Some people say that cause of the grooves is not tooth picking, but this one anthropologist has proposed that picking with abrasive grass stalks caused the grooves.

So, it doesn't really weaken the argument to say, "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," because it's fairly clear that picking with abrasive grass would cause grooves. After all, picking one's teeth with something abrasive would result in tooth wear.

So, the fact that some abrasive grass was present where the teeth do not have grooves shows only that those people did not pick their teeth with grass, not that picking with grass is not the cause of the grooves. Right?

Here's a similar example.

Let's say that we found a tree that had been cut down by an animal. We see beavers in the same area. So, we hypothesize that a beaver cut down the tree. The fact that other trees are still standing where beavers are present would not mean that the tree that had been cut down had not been cut down by a beaver. It would just mean that the beaver had not cut down every tree.

So, this is a similar situation. We don't need all teeth where grass was present to have grooves in order to conclude that grass caused the grooves in teeth that do have grooves.

Thus, the answer to (B) neither weakens nor strengthens the argument.

nikitathegreat · Answer

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?

Raman109 · Answer

Understanding the argument - 
Researchers have long noted strange grooves near the gum lines on dental remains of some early humans. - Background info.

The marks are absent from the teeth of modern-day toothpick users, and have therefore been assumed not to present evidence of tooth picking where they have been present. - Premise and some general claim. Normally, after the general claim, the author will present a contrast. Basically, it says that modern-day toothpick users don't have grooves, so having grooves leads to an assumption that they may not have used toothpicks.

But an anthropologist has recently proposed that the early humans used grass stalks, which, unlike wood, contain abrasive silica, a substance that would facilitate the development of the grooves. - "but" introduces a contrast. The anthropologist proposes that this is not the case; they didn't use the toothpick and may have used a different type than the wooden ones we see now. He says they may have used the toothpicks made from grass stalks and in using those tooth picks they got the grooves. So essentially it challenges the assumption of having goorves means no toothpicks.

Which of the following would, if found to be true, be most useful to the evaluation of the anthropologist's hypothesis?

Option Elimiantion - What would be most useful to evaluate the anthropologist's hypothesis? We have grass stalks and they cause groves. So what happens without grass stalks? they should not have grooves? Right? Yes. But if that's not the case then the argument fall apart.

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 comparison is out of scope.

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. - Out of scope.

D. Abrasive silica derived from grasses and other, similar plants could be useful in the removal of cavity-causing plaque from humans' teeth. - none of our concern. Out of scope.

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. - Meaning, grooves are still happening without grass which calls the anthropologists hypothesis into question. ok.

GMATNinja · Answer

(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!

Gemmie · Answer

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.

The anthropologist proposes that the grooves were caused by using grass stalks with abrasive silica for tooth picking.

If remains with the grooves are found in locations where suitable grass wasn't available, it would challenge the hypothesis.

This finding would directly contradict the idea that the grooves are evidence of using grass stalks for tooth picking.

Let's analyze why the other options are less useful:

A. Similar decay rates:  This doesn't directly address the cause of the grooves, only the health of the teeth.

B. Grass availability:

If dental remains without grooves are found in areas where suitable grass for tooth picking existed, it suggests that access to suitable grass alone does not guarantee the presence of grooves.

However, it doesn't directly address whether early humans with grooves had access to grass with abrasive silica. It only establishes that not all early humans in areas with suitable grass had grooves, which could have other explanations (such as variations in cultural practices or individual behaviors).

In short, this weakens the connection between grooves and grass stalks in some cases, but doesn't necessarily rule it out entirely.

C. Modern toothpick materials:  This supports the idea that modern toothpicks wouldn't leave similar marks, but doesn't address the use of grass stalks in the past.

D. Abrasive silica's usefulness:  This supports the general idea that abrasive materials can clean teeth, but doesn't necessarily confirm grass stalk use.

SmileAndSolve · Answer

Elaborate answers already provided above, just breaking down the passage:

﻿Fact 1:
Researchers have long noted  strange grooves  near the gum lines on dental remains of  some   early humans . 
Fact 2:
The marks are  absent  from the teeth of  modern-day toothpick users , 
Premise 1:
and have therefore been assumed not to present  evidence  of  tooth picking  where they have been present. 
( says since grooves are not present in modern humans who use toothpicks, those early humans did not involve in tooth picking.
i.e. No tooth picking = Grooves
& Tooth Picking = No Grooves
Fact 3:
But an anthropologist has recently proposed that the early humans used grass stalks, which, unlike wood, contain  abrasive silica , a substance that would facilitate the development of the grooves.
Tooth picking with abrasive silica item = Grooves

Hypothesis = Tooth picking with abrasive silica item causes Grooves

Which of the following would,  if   found to be  true , be most useful to the  evaluation of the anthropologist's hypothesis ?

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. 
-Irrelevant to hypothesis.

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.
-Irrelevant to hypothesis.

C. Unlike grass stalks, few modern-day toothpicks contain significant amounts of abrasive silica.
-Fact 3 already provided.

D. Abrasive silica derived from grasses and other, similar plants could be useful in the removal of cavity-causing plaque from humans' teeth.
- Supports the hypothesis that ot was used for tooth picking.

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.
- Points out that Tooth picking with abrasive silica item is not the only thing that causes grooving.

EloiseDU19 · Answer

I have looked down upon this wonderful question. I interpreted  "evaluation"  in the question directly into  "strengthen" , which confused me for quite a moment  .

Gags1611 · Answer

MartyMurray , isn't C saying the exact opposite of the information present in the statement, that toothpicks contain abrasive silica. Meaning it weakens the statement right ?

MartyMurray · Answer

Here's what the passage says:

grass stalks, which, unlike wood, contain abrasive silica

Notice that the point of the passage is that, in containing silica, grass stalks are UNLIKE wood. So, the passage indicates that wood does not contain silica.

Now, here's (C):

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

In this context, "few" means "only a small proportion of." So, the point of (C) is that the vast majority of modern-day toothpicks do NOT contain silica.

Since most modern-day toothpicks are made of wood, this information means something similar to what the passage has already indicated about wood.

SKaur3 · Answer

We are not concerned about tooth decay, specifically and we don't know whether the silica, apart from creating grooves, facilitates tooth decay, so this doesn't help. Let's eliminate.

This doesn't help us in determining or evaluating the hypothesis as it might be the case that some early humans don't prefer tooth picking.

Let's think about this in a way, if we answer, yes to this statement, so few modern toothpicks have significant amounts of abrasive silica, so here are two things

1. That might correspond to a few people having grooves in their gums, but we are not sure how many people use it.

2. Also, this info is already provided in the statement, hence doesn’t add up any new info.

Or if the answer is no, then it will contradict the premise 
Thus, eliminate it.

Here we are not concerned about plague in the tooth, we are concerned about grooves in the gums. Thus, eliminate it.

Let's try the same way of answering, yes, or no, and evaluating.

If we assume that this statement is positive, then in that case, the anthropologist hypothesis would be wrong that is, it would be wrong to conclude that they used grass stalks for tooth picking

And if we assume the statement is negative, then it will support the hypothesis.

So, in this case, answering yes, and no determines the validity of the argument. Thus, Keep E.

soumyab12 · Answer

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.

KarishmaB · Answer

Anthropologist's Hypothesis: The early humans used grass stalks (to pick their teeth), which contain abrasive silica, a substance that would facilitate the development of the grooves. 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. Tooth decay does not tell us whether they used grass stalks to pick their teeth. There is no link given between them. 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. This option says that at some places the grass was there but there were no grooves in human teeth. This doesn't impact given hypothesis at all. It is not necessary that everyone who could find that grass should have picked their teeth with it. Not everyone today uses toothpicks. Similarly, some early humans might have picked their teeth and hence the grooves developed. What we need to find is whether the humans who had the grooves in their teeth had access to the grass. C. Unlike grass stalks, few modern-day toothpicks contain significant amounts of abrasive silica. We are already told that modern-day toothpicks (made of wood) do not contain abrasive silica. D. Abrasive silica derived from grasses and other, similar plants could be useful in the removal of cavity-causing plaque from humans' teeth. This option gives us an advantage abrasive silica could have for the teeth. This option is interesting but we don't know whether the early humans knew about the plaque removal properties of abrasive silica found in grass. So let's hold on to it. 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 option tells us that at some places where grooves in teeth were found, grass was not found. So then it seems that early humans did not use grass stalks for tooth picking. This is useful to evaluate whether early humans used grass or not. This indicates that they did not. Groove making object would likely be common to all places where grooves in teeth have been found. Answer (E) Another discussion on Useful to Evaluate: https://youtu.be/1JtHjH1lWZc

Researchers have long noted strange grooves near the gum lines on

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