The ancient Nubians inhabited an area in which typhus occurred, yet surprisingly few of their skeletons show the usual evidence...

GMAT Critical Reasoning : (CR) Questions

Source: Official Guide

Critical Reasoning

Assumption

HARD

...

Notes

Post a Query

The ancient Nubians inhabited an area in which typhus occurred, yet surprisingly few of their skeletons show the usual evidence of this disease. The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil. This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread. Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.

Which of the following is an assumption on which the argument relies?

The tetracycline deposits did not form after the bodies were buried.

The diseases other than typhus to which the ancient Nubians were exposed would not be affected by tetracycline.

Typhus is generally fatal.

Tetracycline is not rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.

Bread and beer were the only foods eaten by the ancient Nubians which could have contained tetracycline.

Solution

Passage Analysis:

Text from Passage	Analysis
The ancient Nubians inhabited an area in which typhus occurred, yet surprisingly few of their skeletons show the usual evidence of this disease.	What it says: Ancient Nubians lived where typhus was present, but their skeletons rarely show signs of having this disease What it does: Sets up a puzzle - why didn't more Nubians get typhus when it was around? What it is: Author's observation about historical evidence
The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil.	What it says: Nubian skeletons contain tetracycline, which is an antibiotic made by bacteria in their soil What it does: Introduces a potential clue that might explain the typhus puzzle What it is: Archaeological finding Visualization: Nubian soil → bacteria → tetracycline (antibiotic) → found in skeletons
This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread.	What it says: The tetracycline-producing bacteria grows well on dried grain that Nubians used for beer and bread What it does: Shows how the antibiotic could have gotten into Nubian food regularly What it is: Scientific fact about bacterial growth Visualization: Dried grain → bacteria flourishes → beer & bread (daily food)
Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.	What it says: The tetracycline in Nubian food likely caused the low rates of typhus What it does: Connects all the previous facts to solve the initial puzzle What it is: Author's conclusion Visualization: Tetracycline in food → protects against typhus → explains low disease rates

Argument Flow:

The argument starts with a medical mystery - why didn't ancient Nubians get typhus much despite living where it occurred? It then presents evidence about tetracycline in their skeletons, explains how this antibiotic got into their diet through bacteria on grain used for bread and beer, and concludes this dietary antibiotic protected them from typhus.

Main Conclusion:

Tetracycline in Nubian food probably explains why ancient Nubians had low rates of typhus disease.

Logical Structure:

This is a causal explanation argument. We have an observed effect (low typhus rates) that needs explaining, and the author proposes a cause (dietary tetracycline) by connecting several pieces of evidence: tetracycline presence in skeletons, its source from soil bacteria, and how that bacteria got into their daily food through grain.

Prethinking:

Question type:

Assumption - We need to find what the argument takes for granted but doesn't explicitly state. For assumption questions, we identify ways the conclusion could be falsified while respecting the given facts.

Precision of Claims

The argument makes specific claims about causation (tetracycline explains low typhus), effectiveness (tetracycline protects against typhus), and consumption patterns (Nubians regularly consumed tetracycline through food).

Strategy

The argument concludes that tetracycline in food explains low typhus rates among Nubians. We need to find unstated assumptions that must be true for this conclusion to work. We'll think about what could make this explanation fall apart - like if tetracycline doesn't actually fight typhus, or if Nubians didn't actually consume enough of it, or if there are other explanations for the low typhus rates.

Answer Choices Explained

The tetracycline deposits did not form after the bodies were buried.

CORRECT - This identifies a crucial gap in the argument. The entire explanation assumes that tetracycline deposits in skeletons reflect what living Nubians consumed, not post-mortem contamination. If tetracycline formed after burial, it wouldn't explain typhus protection in living people. The argument takes this for granted but never proves it, making this a necessary assumption.

The diseases other than typhus to which the ancient Nubians were exposed would not be affected by tetracycline.

INCORRECT - The argument only claims tetracycline prevented typhus specifically. Whether it affected other diseases is irrelevant to the conclusion. The argument doesn't need to assume anything about tetracycline's effectiveness against other diseases - it only needs the typhus connection to work.

Typhus is generally fatal.

INCORRECT - The argument focuses on incidence (how often typhus occurred), not fatality rates. Whether typhus killed people or just made them sick doesn't matter for the conclusion. The low occurrence of typhus evidence in skeletons could be explained by tetracycline prevention regardless of how deadly typhus was.

Tetracycline is not rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.

INCORRECT - While this seems relevant since bread and beer require processing, the argument doesn't actually depend on this. Even if processing reduced tetracycline effectiveness somewhat, as long as some protection remained, it could still explain the low typhus rates. The argument doesn't require perfect tetracycline preservation.

Bread and beer were the only foods eaten by the ancient Nubians which could have contained tetracycline.

INCORRECT - The argument never claims bread and beer were the only tetracycline sources. It just explains how tetracycline got into the Nubian diet through these staples. Other sources wouldn't contradict the conclusion - they might even strengthen it by providing more tetracycline protection.

Rate this Solution

Tell us what you think about this solution

...

Forum Discussions

Start a new discussion

Post

Previous Attempts

Loading attempts...