Critical Reasoning

Agricultural societies cannot exist without staple crops. Several food plants, such as kola and okra, are known to have been domesticated in western Africa, but they are all supplemental, not staple, foods. All the recorded staple crops grown in western Africa were introduced from elsewhere, beginning, at some unknown date, with rice and yams. Therefore, discovering when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there. Which of the following is an assumption on which the argument depends?

A. People in western Africa did not develop staple crops that they stopped cultivating once rice and yams were introduced.
B. There are no plants native to western Africa that, if domesticated, could serve as staple food crops.
C. Rice and yams were grown as staple crops by the earliest agricultural societies outside of western Africa.
D. Kola and okra are better suited to growing conditions in western Africa than domesticated rice and yams are.
E. Kola and okra were domesticated in western Africa before rice and yams were introduced there.

what's the logic behind discarding option C

richachampion wrote:what's the logic behind discarding option C

The main problem with C is the word "earliest," Clearly yams and rice had to have been cultivated somewhere outside of Western Africa. But when they were first cultivated isn't clear. Maybe the earliest agricultural societies produced mostly wheat and it was a later society that produced the rice and yams that were later brought to Western Africa.

X = All the recorded staple crops are grown in western Africa were introduced from elsewhere, beginning, at some unknown date, with rice and yams.

Conclusion =Y → Therefore, discovering when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there.

I have recently seen a pattern in the GMAC questions.

X, therefore Y. Did you see or realize something?

X, THEREFORE Y.

How can you break this equation, which is stated above.
Let's do this.

What if they were not all brought from "elsewhere", but developed and were grown in the western Africa itself.

And this possibility is what the assumption is. The question assumed that western Africa never developed and grown the staple crop.

So what I was saying was X, THEREFORE Y.
The assumption lies in X and can be found by attacking X.

Right?

richachampion wrote:X = All the recorded staple crops are grown in western Africa were introduced from elsewhere, beginning, at some unknown date, with rice and yams.

Conclusion =Y → Therefore, discovering when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there.

I have recently seen a pattern in the GMAC questions.

X, therefore Y. Did you see or realize something?

X, THEREFORE Y.

How can you break this equation, which is stated above.
Let's do this.

What if they were not all brought from "elsewhere", but developed and were grown in the western Africa itself.

And this possibility is what the assumption is. The question assumed that western Africa never developed and grown the staple crop.

So what I was saying was X, THEREFORE Y.
The assumption lies in X and can be found by attacking X.

Right?

It sounds as though you're employing the same logic we use when we negate the answer choices - if 'x' is assumed in a given argument, then "not x" should undermine the conclusion. True. So let's use that approach here.

C negated: Rice and yams were NOT grown as staple crops by the earliest agricultural societies outside of western Africa. This has no effect on the conclusion. If the earliest agricultural society were active in, say, 8500 B.C., and this society was not growing rice, but a later one in, say, 7000 B.C. did grow rice, it could certainly be the case that the rice was transferred from this later society to Western Africa, and that this rice was the first instance of crop domestication in Western Africa. Because the negation of C does not undermine the conclusion, this cannot be the correct answer.

A negated: People in western Africa DID develop staple crops that they stopped cultivating once rice and yams were introduced. The argument is predicated on the notion that rice and yams were the first crop domesticated in Western Africa. If there were some earlier, discontinued crop, we can no longer persuasively argue that knowing when rice and yams were introduced can tell us when agricultural societies in Western Africa began. Because the negation of A undermines the conclusion, we know this is our answer.