Agricultural societies cannot exist without staple crops...

[prashant.ranjan]

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.

I came with up with wrong answer choice in this question. I could understand why (A) is the correct answer choice - since its negation totally shatters the conclusion, but I would like some assistance from MGMAT experts in confirming whether my following understanding for eliminating incorrect answer choices (B) and (C) is correct.

Following is my attempt to strike out the incorrect answer choices.
(B) On negation this statement becomes:
There are SOME plants native to western Africa that, if domesticated, could serve as staple food crops.

Even if there were/are some plants that are staple crops and are native to Western Africa, we don’t know whether these staple crops were planted before the plantation of rice/yams by the agricultural societies, or after staple crops rice/yams were introduced in Western Africa. If it was the former case then it would weaken the conclusion and hence can be a valid assumption. If it is the latter case, then it’s not going to affect the conclusion anyway. Since we don’t know of this information, so this can’t be an assumption - since an assumption is something that must be true for the conclusion to be valid.
(C) The following statements in the passage already establish the fact that Rice/yams were grown outside by agricultural societies.
"Agricultural societies cannot exist without staple crops. All the recorded staple crops grown in western Africa were introduced from elsewhere..........with rice and yams".

Since we can already infer this from the passage and the assumption introduces no additional info apart from what is already stated in the passage, this can’t be an assumption.
Moreover when I negate this statement,
Rice and yams were not grown as staple crops by the earliest agricultural societies outside of western Africa.
Still it doesn’t negate the conclusion. There can still be a possibility that agricultural societies with their advent in western Africa, brought staple crops Rice/yams with them.

Thanks and Regards
Prashant
_____
BIG Fan :)

[Willy]

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.

I came with up with wrong answer choice in this question. I could understand why (A) is the correct answer choice - since its negation totally shatters the conclusion, but I would like some assistance from MGMAT experts in confirming whether my following understanding for eliminating incorrect answer choices (B) and (C) is correct.

Following is my attempt to strike out the incorrect answer choices.
(B) On negation this statement becomes:
There are SOME plants native to western Africa that, if domesticated, could serve as staple food crops.

Even if there were/are some plants that are staple crops and are native to Western Africa, we don’t know whether these staple crops were planted before the plantation of rice/yams by the agricultural societies, or after staple crops rice/yams were introduced in Western Africa. If it was the former case then it would weaken the conclusion and hence can be a valid assumption. If it is the latter case, then it’s not going to affect the conclusion anyway. Since we don’t know of this information, so this can’t be an assumption - since an assumption is something that must be true for the conclusion to be valid.
(C) The following statements in the passage already establish the fact that Rice/yams were grown outside by agricultural societies.
"Agricultural societies cannot exist without staple crops. All the recorded staple crops grown in western Africa were introduced from elsewhere..........with rice and yams".

Since we can already infer this from the passage and the assumption introduces no additional info apart from what is already stated in the passage, this can’t be an assumption.
Moreover when I negate this statement,
Rice and yams were not grown as staple crops by the earliest agricultural societies outside of western Africa.
Still it doesn’t negate the conclusion. There can still be a possibility that agricultural societies with their advent in western Africa, brought staple crops Rice/yams with them.

Thanks and Regards
Prashant
_____
BIG Fan :)

I think your reasoning is perfect. We can also infer answer choice B from the above highlighted part by me. BTW your negation test was okay!

[RonPurewal]

prashant,

your reasoning for (b) is on target.

for (c), not so much.
(c) is wrong because it's irrelevant to the argument, which is concerned only with crops grown in western africa. facts about the timeline of agriculture in other regions don't matter.

[gmat.acer]

prashant,

your reasoning for (b) is on target.

for (c), not so much.
(c) is wrong because it's irrelevant to the argument, which is concerned only with crops grown in western africa. facts about the timeline of agriculture in other regions don't matter.

I am confused why facts about the timeline of agriculture in other regions don't matter? If we just remove the word 'earliest' from (C), I think such modified (C) would be a correct assumption. Could some expert explain please?

I believe that following two statements in the passage inherently assume that staple crops came from outside of western Africa.

(1) "Agricultural societies cannot exist without staple crops."

(2) "All the recorded staple crops grown in western Africa were introduced from elsewhere.."
elsewhere = outside of western Africa.

I didn't select (C) because it says "earliest societies". It says staple crops were grown by the earliest agricultural societies outside of western Africa.
I believe it is not necessary to assume that these societies who were growing staple crops were the "earliest" societies outside Africa. It is only necessary that these are some societies OUTSIDE western Africa who first grew staple crops IN western Africa, because it could be possible that outside of western Africa there were some societies earlier than these ones who grew staple crops but did not bring them to western Africa.

So, I believe if we remove the word "earliest" from (C), will it be a correct answer choice?

Rice and yams were grown as staple crops by agricultural societies outside of western Africa.

Negating this modified (C) would weaken premise#(1) mentioned above.

I understand that negated (A) completely shatters the conclusion, and thus (A) is the correct assumption. Whereas negated (C) weakens premises.

But in the absence of (A), can above modified (C) be a correct assumption?

[jlucero]

I'm repeating what Ron already said: C is irrelevant to the argument.

Conclusion: Discovering when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there.

Assumption: Rice and yams must have been the earliest crops ever used by agricultural societies IN WESTERN AFRICA.

Answer C: Rice and yams were grown as staple crops by the (earliest) agricultural societies outside of western Africa. (who cares about any place other than western Africa- irrelevant)

[gbyhats]

Hi dear Manhattan instructors

Can you explain a little bit deeper how we to rule out choice (B)?
(I have no double that choice A is correct)

[RonPurewal]

remember that "assumption" means something that is NECESSARY for the argument work. (an assumption is NOT just "something that supports/strengthens an argument"!)

choice B is way too strong to be necessary.

see, the point is this:
the FACT is that, to date, no staple crops have actually been domesticated in western africa.
this is the only thing that's relevant here: the fact that, so far, people have not actually created a staple crop in that area of the world.

B takes it to a whole new level, though. basically, B is saying that people CAN'T ever create a staple crop in that region-- even if they want to-- because no potential staple crop even exists.
it should be clear that this is much too strong to be necessary. (even if hundreds of such potential staple crops exist... well, it doesn't matter, because no one has domesticated any of them.)

[RonPurewal]

you can also kill B using the negation test.

if you negate B, you get:
There are plants native to western Africa that, if domesticated, could serve as staple food crops.

...to which the answer is:
"ok, great!
but (according to the passage) no one has actually domesticated any of them, so i don't care." the argument is not affected at all. (remember that, when an actual assumption is negated, the argument should be completely destroyed/invalidated.)

[gbyhats]

Hi dear Ron,

Thank you so much for your explanation

remember that "assumption" means something that is NECESSARY for the argument work. (an assumption is NOT just "something that supports/strengthens an argument"!)

choice B is way too strong to be necessary.

That's interesting! I never think about this question in this way!

you can also kill B using the negation test.

Whoa! You killed B on the spot! You totally convinced me, thank you for clearing up my question!

[RonPurewal]

this isn't a matter of rhetoric (i.e., there's no "convincing" to do). rather, this is simply a matter of knowing what the word "assumption" means.

[gbyhats]

this isn't a matter of rhetoric (i.e., there's no "convincing" to do). rather, this is simply a matter of knowing what the word "assumption" means.

Hahaha, yes you are right! What you say is fact -- there is not a "convincing" or "not convincing" fact.

[RonPurewal]

yep.

more generally, there shouldn't be any "convincing" at all on this exam.

this exam has to be administered almost a million times a year, without controversy. thus, EVERY question should, ultimately, have an essentially "black-and-white" quality to it.

[said79]

choice A states that people did not develop staple crops THAT THEY STOPPED cultivating once rice and yam were introduced.

my understanding is that there used to be staple crops (since they stopped cultivating ) earlier than when rice and yam were introduced. Isn't this statement self contradictory? how can one stop cultivating when he/she did not even develop it in the first place?.

please clarify if my thinking is wrong.

thanks in advance

suhas.

[RonPurewal]

choice A is the negation of "People in western Africa developed staple crops that they stopped cultivating once rice and yams were introduced".

that sentence should make perfect sense -- so, just think of choice A as saying "that sentence is false".

[RonPurewal]

by the way, i've noticed that no one has posted the original source of this problem anywhere in this thread. there can be absolutely no further discussion of this problem until someone posts the original source, as per the forum rules.
thanks.