Scientists studying fossils of a species of dinosaur found stones in the dinosaurs' stomach area. These dinosaurs were vegetarians, but...

GMAT Critical Reasoning : (CR) Questions

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Critical Reasoning

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Scientists studying fossils of a species of dinosaur found stones in the dinosaurs' stomach area. These dinosaurs were vegetarians, but their teeth could not have chewed a sufficient quantity of vegetation well enough to provide nutrition to support their large size. Thus, the stones may have served to help grind up the dinosaurs' food, just as happens with ostriches and some other modern birds. Alternatively the stones may have served as nutritional supplements, supplying minerals not found in vegetation in large enough quantities.

In order to help decide between the two hypotheses for the stones' function, which of the following would it be most useful to know?

Whether the stones had sufficient volume to efficiently grind the vegetation that served as the dinosaurs food

Whether the stones swallowed by ostriches or other modern birds serve to provide any nutritional minerals

Whether stones were found in the stomachs of related species of dinosaurs

Whether any large modern animals typically eat the same sort of vegetation as did these dinosaurs

Whether there is any evidence of the presence of the relevant nutritional minerals in the fossilized bones of these dinosaurs

Solution

Passage Analysis:

Text from Passage	Analysis
Scientists studying fossils of a species of dinosaur found stones in the dinosaurs' stomach area.	What it says: Scientists discovered stones inside fossilized dinosaurs' stomachs What it does: Sets up the mystery we need to solve - why are there stones in dinosaur stomachs? What it is: Study finding
These dinosaurs were vegetarians, but their teeth could not have chewed a sufficient quantity of vegetation well enough to provide nutrition to support their large size.	What it says: These plant-eating dinosaurs had a problem - their teeth weren't good enough to chew enough food for their huge bodies What it does: Creates a puzzle that connects to the stones - if they couldn't chew well, maybe the stones helped somehow What it is: Study finding Visualization: Large dinosaur + weak teeth + massive food needs = problem that needs solving
Thus, the stones may have served to help grind up the dinosaurs' food, just as happens with ostriches and some other modern birds.	What it says: First theory - stones worked like a food processor to grind up plants, similar to how ostriches use stones today What it does: Offers the first possible explanation for the stone mystery using modern bird behavior as evidence What it is: Author's hypothesis
Alternatively the stones may have served as nutritional supplements, supplying minerals not found in vegetation in large enough quantities.	What it says: Second theory - stones were like vitamin pills, giving dinosaurs minerals they couldn't get enough of from plants alone What it does: Presents a competing explanation that shifts focus from mechanical grinding to nutritional needs What it is: Author's alternative hypothesis

Argument Flow:

"The argument starts with an observation (stones in dinosaur stomachs), then establishes a problem (dinosaurs couldn't chew well enough), and finally presents two competing theories to explain how the stones might have solved this problem."

Main Conclusion:

"There are two possible explanations for why dinosaurs had stones in their stomachs - either for grinding food or for providing essential minerals."

Logical Structure:

"This isn't a traditional argument with one conclusion. Instead, it's a hypothesis-generating passage that uses the evidence (inadequate teeth + large size + stones present) to develop two competing theories that both could explain the same phenomenon."

Prethinking:

Question type:

Evaluate - We need to find information that would help us decide between two competing hypotheses about why dinosaurs had stones in their stomachs

Precision of Claims

The passage presents two specific theories: stones as mechanical grinders (like ostriches) versus stones as mineral supplements. Both are presented as equally plausible explanations for the same observed phenomenon

Strategy

For evaluate questions, we need to think of what information would clearly point toward one hypothesis over the other. We want evidence that would strongly support the grinding theory OR strongly support the nutritional supplement theory. The best evaluation criteria will create a clear distinction between these two competing explanations

Answer Choices Explained

Whether the stones had sufficient volume to efficiently grind the vegetation that served as the dinosaurs food

This directly tests the mechanical grinding hypothesis by asking if the stones were actually capable of doing the job they're supposed to do according to theory 1. If the stones had sufficient volume to grind vegetation efficiently, this would strongly support the grinding hypothesis. If they lacked sufficient volume, it would weaken the grinding theory and make the nutritional supplement theory more plausible. This creates a clear way to distinguish between our two competing explanations.

Whether the stones swallowed by ostriches or other modern birds serve to provide any nutritional minerals

This asks whether stones in modern birds provide nutritional minerals. However, this doesn't help us decide between hypotheses because even if bird stones do provide some minerals, it doesn't tell us whether dinosaur stones primarily served for grinding or nutrition. The passage already establishes that bird stones are used for grinding, so learning they also provide some minerals doesn't resolve our dinosaur mystery.

Whether stones were found in the stomachs of related species of dinosaurs

Knowing whether related dinosaur species also had stomach stones might be interesting for understanding dinosaur evolution, but it doesn't help us determine the function of stones in our specific species. Related species could have used stones for the same purpose or different purposes, so this information doesn't distinguish between grinding versus nutritional functions.

Whether any large modern animals typically eat the same sort of vegetation as did these dinosaurs

Information about what modern animals eat compared to these dinosaurs doesn't directly address either hypothesis about stone function. Whether modern animals eat similar vegetation tells us nothing about whether stones in dinosaur stomachs served for grinding food or providing minerals.

Whether there is any evidence of the presence of the relevant nutritional minerals in the fossilized bones of these dinosaurs

This asks about evidence of nutritional minerals in dinosaur bones. While this might seem relevant to the nutritional supplement hypothesis, it's actually not decisive. Even if we found these minerals in bones, we couldn't conclude the stones provided them - the dinosaurs might have gotten adequate minerals from vegetation and used stones purely for grinding. Conversely, absence of minerals in bones wouldn't definitively rule out the nutritional hypothesis since fossilization might not preserve all mineral evidence.

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