Researchers have long noted strange grooves near the gum lines on dental remains of some early humans. The marks are...
GMAT Critical Reasoning : (CR) Questions
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?
Passage Analysis:
| Text from Passage | Analysis |
|---|---|
| Researchers have long noted strange grooves near the gum lines on dental remains of some early humans. |
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| 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. |
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| 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. |
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Argument Flow:
The passage starts with a scientific puzzle (grooves on ancient teeth), explains why the obvious answer was rejected (modern toothpick users don't have grooves), then introduces a new theory that could solve the mystery (grass stalks with silica could cause grooves).
Main Conclusion:
Early humans may have used grass stalks (containing abrasive silica) for tooth picking, which would explain the grooves found on their teeth.
Logical Structure:
The anthropologist's hypothesis is supported by the key difference between materials: grass contains abrasive silica while wood doesn't, which could explain why early humans developed grooves but modern toothpick users don't.
Prethinking:
Question type:
Evaluate - We need to find information that would help us determine whether the anthropologist's hypothesis about grass stalks creating grooves is correct or not
Precision of Claims
The key claim is that early humans used grass stalks (containing abrasive silica) for tooth picking, which created the grooves that modern wooden toothpicks cannot create
Strategy
For evaluate questions, we need to think of assumptions underlying the hypothesis and create scenarios that would either strongly support or strongly contradict the anthropologist's theory when taken to extremes. We want information that directly tests the core logic of the hypothesis.
This tells us about tooth decay rates between grooved and non-grooved teeth. While this might be interesting from a dental health perspective, it doesn't help us evaluate whether grass stalks caused the grooves. The anthropologist's hypothesis is specifically about what created the grooves, not about dental health outcomes. This information doesn't test the core claim.
This describes finding early humans WITHOUT grooves in places where grass WAS available. This is somewhat relevant because it shows that access to grass doesn't guarantee grooves, but it doesn't strongly challenge or support the hypothesis. There could be many reasons why someone with access to grass might not have grooves (personal preference, other cleaning methods, etc.). This provides weak evidence at best.
This restates information we already know - that modern toothpicks (wood) don't contain silica while grass does. This doesn't add new information to help us evaluate the hypothesis. We already know this distinction is central to the anthropologist's theory, so confirming it again doesn't help us test whether the theory is correct.
This tells us that silica from grass could be useful for removing plaque. While this supports the idea that grass could be effective for dental care, it doesn't directly test whether early humans actually used grass stalks or whether grass stalks specifically caused the grooves we observe. Effectiveness doesn't prove historical usage.
This would show grooves existing in places where no suitable grass was available during the early humans' lifetimes. This directly contradicts the core of the anthropologist's hypothesis. If grooves appear where grass wasn't available, then grass stalks couldn't have caused those grooves. Conversely, if grooves only appear where grass was available, it would strongly support the hypothesis. This provides the most direct test of the theory's validity.