Question
Some anthropologists believe that the genetic homogeneity evident in the world’s people is the result of a “population bottleneck” — at some time in the past our ancestors suffered an event, greatly reducing their numbers and thus our genetic variation.
Option A
Option B
Option C
Option D
Option E
(This question is from Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)
Solution
Sentence Analysis
The sentence talks about what some anthropologists believe.
What do they believe? That the genetic homogeneity is the result of a population bottleneck.
What kind of homogeneity? The homogeneity that is evident in the world’s people.
Then, the sentence has em dash, which is a very versatile punctuation and can provide any kind of additional information relevant to the sentence. In this question, em dash is used to enclose an independent clause.
As we read the sentence after em dash, we encounter an independent clause. This part says that at some time in the past, our ancestors suffered an event. No information about the ‘event’ is provided. The sentence then introduces a verb-ing (reducing) acting as a clause modifier and providing the result of the previous clause. The sentence means that as a result of our ancestors’ suffering of an event, the numbers of our ancestors and thus our genetic variation greatly reduced. Given the lack of information about “an event”, it doesn’t seem logical to talk about the result of the event. Also, the verb-ing modifier (reducing) doesn’t make sense with the subject of the clause (our ancestors).
The original sentence thus has the abovementioned problems.
Option Analysis
(A) Incorrect. For the reasons explained in the sentence analysis.
(B) Correct. This option corrects both the problems in the original sentence by replacing the verb-ing modifier with the relative clause (that greatly reduced). In this option, the relative clause modifies “event” and thus provides additional information about it. Our ancestors suffered an event. What kind of event? That greatly reduced their numbers and thus our genetic variation.
(C) Incorrect. The non-underlined part “and thus our genetic vision” doesn’t make sense within the sentence structure of this option.
(D) Incorrect. For the following reasons:
- We need a preposition (at) with “some time” for it modify the clause “our ancestors suffered”. Or we can use “sometime”, which is an adverb, standalone. For the difference between some time and sometime, please refer this article. In general, “sometime” means “at some point”, and “some time” means “a period of time”.
- “from which” construction stands for “their numbers were greatly reduced from the event”. Clearly, the numbers were reduced not FROM the event but BY the event.
- The error of option C
(E) Incorrect. For the following reasons:
- Error no. 1 of option D
- The purpose of “that” is not clear. It illogically seems to modify “past” or “some time in the past”.
- “so as to” indicates purpose. This option illogically means that the ancestors suffered with an intention to reduce their numbers.
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Option C another error in my opinion – use of “so that” is incorrect. Further 1st error in option C – ” sometimes is used standalone” , hence it i not an error as per your explanation.
Under explanation to option D, u have mentioned – Error no. 3 of option C, however u hv stated only 2 errors.
Hi Sej,
“so that” is not incorrect since “so that” is also used to mean “with the result that”. Refer this link for more details. Thank you for the other corrections.
Sir, please explain a bit about modifiers in this question.
“at some time in the past our ancestors suffered an event, greatly reducing their numbers and thus our genetic variation.”
according to me, preceding ” an event ” can be noun and the modifier is noun modifier.
Mistake is that we cannot use “and” between reason and its effect as given in question stem.
please clarify.
I’m sorry, Mukesh. Didn’t understand your query. Would you mind explaining it again?
Sir,
In “at some time in the past our ancestors suffered an event, greatly reducing their numbers and thus our genetic variation.”
“an event” is the noun modified by ING modifier. and ING modifier is explaining the effects of event. it is perfectly fine.
May be mistake is that we cannot use “and” between reason and its effect in ING Modifier.
” reducing their numbers and THUS our genetic variation.”
Hope it clarify.
A comma+verb-ing at the end of a clause never modifies the preceding noun. Even if we remove the comma, it’d still be wrong since “our ancestors suffered an event reducing their numbers” is wrong; the correct version is “our ancestors suffered an event that reduced their numbers”
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