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# Some anthropologists believe that the genetic homogeneity

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Some anthropologists believe that the genetic homogeneity [#permalink]

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22 Jun 2012, 02:28
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The Official Guide for GMAT Review 2017

Practice Question
Question No.: SC 736
Page: 695

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.

(A) at some time in the past our ancestors suffered an event, greatly reducing their numbers

(B) that at some time in the past our ancestors suffered an event that greatly reduced their numbers

(C) that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced

(D) some time in the past our ancestors suffered an event from which their numbers were greatly reduced

(E) some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,
[Reveal] Spoiler: OA

Last edited by hazelnut on 09 Dec 2017, 07:00, edited 1 time in total.
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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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25 Jun 2012, 21:12
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In answer choice (A) there is a problem with modification. (A) is implying that our ancestors greatly reduced their own numbers (this is incorrect because it was the event that greatly reduced ancestors). When we have an independent clause followed by a participle phrase (one that starts with a gerund and serves as an adjective clause), the participle phrase modifies the subject of the sentence.

In non-grammarese: 'ancestors' is the subject of the independent clause, 'at some time...' and because of the comma after event, we have the incorrect meaning. It was not the ancestors but an event that 'reduced their numbers.'

Therefore, we want to make sure that it is clear that 'event' is 'greatly reducing the numbers.' One way to fix that is by using the relative pronoun 'that.' In (B), we have 'an event that greatly reduced their numbers' that does a good job of correcting the error in (A).

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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22 Jun 2012, 06:58
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A at some time in the past our ancestors suffered an event, greatly reducing their numbers ------ A hyphen is not the tool to connect two ICs.
B that at some time in the past our ancestors suffered an event that greatly reduced their numbers -------- ‘that ’ is the right connector ---correct choice.
C that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced ------- altered notion; it looks as if the ancestors suffered a calamity in order to reduce their numbers.
D some time in the past our ancestors suffered an event from which their numbers were greatly reduced -------- conjugation of two ICs with hyphenation is wrong.
E some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly, ------ same as in D

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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31 Oct 2012, 23:14
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COMMA + VERBing should refer to the SUBJECT of the preceding clause. In A, reducing seems to refer to our ancestors, implying that OUR ANCESTORS were greatly reducing their numbers. The intended meaning here is that an EVENT greatly reduced their numbers. Eliminate A.

So that (in C) and so as (in E) imply PURPOSE. The result is a strange meaning: that our ancestors suffered for the PURPOSE of reducing their numbers. Not the intended meaning. Eliminate C and E.

In D, which seems to refer to an event, implying that our ancestors' numbers were reduced FROM an event -- a nonsensical meaning. Eliminate D.

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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25 Sep 2012, 23:21
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divineacclivity wrote:
ChrisLele wrote:
In answer choice (A) there is a problem with modification. (A) is implying that our ancestors greatly reduced their own numbers (this is incorrect because it was the event that greatly reduced ancestors). When we have an independent clause followed by a participle phrase (one that starts with a gerund and serves as an adjective clause), the participle phrase modifies the subject of the sentence.

In non-grammarese: 'ancestors' is the subject of the independent clause, 'at some time...' and because of the comma after event, we have the incorrect meaning. It was not the ancestors but an event that 'reduced their numbers.'

Therefore, we want to make sure that it is clear that 'event' is 'greatly reducing the numbers.' One way to fix that is by using the relative pronoun 'that.' In (B), we have 'an event that greatly reduced their numbers' that does a good job of correcting the error in (A).

Use of 'that' in 'that greatly reduced their numbers" sounds good as you explained but how's the use of 'that' in "that at some time in the past.." justified. Please explain.
If "that at some time in the past.." were parallel to "that the genetic homogeneity..", shouldn't the sentence rather look like:
Some people believe that X and that Y.
The sentence as it looks to me actually is like this:
Some people believe something population bottleneck - definition of population bottleneck.

I rejected option B because 'that' in 'that at some time in the past...' sounded awkward and I got the question wrong

I had thought on the same lines initially (that X and that Y) - but closely looking at these two choices you would notice there is a clear change of meaning in the second choice (C)

we can replace 2nd "that" in B with "which" and sentence makes same sense. so its not ( that X and that Y)
B that at some time in the past our ancestors suffered an event that greatly reduced their numbers

"so that" in this means "because of". It conveys as if the ancestors suffered an event to cause a reduction in their own numbers.
C that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced

Hope it makes sense.
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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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14 Jun 2013, 05:40
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ChrisLele wrote:
In answer choice (A) there is a problem with modification. (A) is implying that our ancestors greatly reduced their own numbers (this is incorrect because it was the event that greatly reduced ancestors). When we have an independent clause followed by a participle phrase (one that starts with a gerund and serves as an adjective clause), the participle phrase modifies the subject of the sentence.

In non-grammarese: 'ancestors' is the subject of the independent clause, 'at some time...' and because of the comma after event, we have the incorrect meaning. It was not the ancestors but an event that 'reduced their numbers.'

Therefore, we want to make sure that it is clear that 'event' is 'greatly reducing the numbers.' One way to fix that is by using the relative pronoun 'that.' In (B), we have 'an event that greatly reduced their numbers' that does a good job of correcting the error in (A).

Hi,
I am bit confused about your explanation, I thought that a participle phrase (gerund) will modify the entire independent clause - in this case the fact that "our ancestors suffered an event"
Example (Taken from MGMAT just to make sure I don't introduce something estrange):
Crime has recently decreased in our neighborhood, leading to a rise in property values

I may be missing something in your explanation, so it will be great if you can expand a bit more on it.

I originally had chosen A, not thinking about the required parallelism: Anthropologist believed that x - that y. I didn't think it made sense to make those two clauses parallel because of the lack of 'and', and thus I figured that the clause after the dash ('=') was just emphasizing the definition of a 'population bottleneck'.

I hope this thread is not to old.

Thanks,

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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24 Apr 2014, 21:41
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kinjiGC wrote:
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.

(A) at some time in the past our ancestors suffered an event, greatly reducing their numbers
(B) that at some time in the past our ancestors suffered an event that greatly reduced their numbers
(C) that some time in the past our ancestors suffered an event so that their numbers were greatly reduced,
(D) some time in the past our ancestors suffered an event from which their numbers were greatly reduced
(E) some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,

Meaning: Some anthropologists believe that the genetic homogeneity evident in the world's people is the result of a "population bottleneck". Population bottleneck – an event that occurred sometime back in the past which greatly reduced their numbers and thus our genetic variation.

Option A) “greatly reducing their numbers” – Verb-ing modifier comma separated, so presenting (modifying) more information about the preceding clause “at some time in the past our ancestors suffered an event” which is incorrect as the event reduced their numbers.

Option C) so that presents reason which is incorrect.

Option D) “from which” is incorrect. The correct sentence would be “some time in the past our ancestors suffered an event that greatly reduced their numbers”.

Option E) “so as” provides an intent.

My confusion is “that” in Option B)
that should replace “population bottleneck”
So the sentence becomes “population bottleneck at some time in the past our ancestors suffered an event that greatly reduced their numbers” – doesn’t look correct to me.

I know after the hyphen “-” the modifier comes which provides more information about the preceding noun.

Dear Kinjal,

The punctuation mark referred to by you is technically called a “dash”. Yes, it has a slightly less fancy name than the “hyphen”.

Moving on, the dash can be used in multiple ways. In the sentence at hand, it has been used to elaborate on what the author has mentioned before the dash. If you observe, the portion after the dash not only expands on the “bottleneck” bit but also on how the genetic homogeneity is the result of the mentioned bottleneck. Accordingly, if I were to draw a parallel structure it would be something on the following lines:

Mariana believes that altruism exists even in today’s day and age — that people can help others without any selfish motives is not an idea that is too unrealistic to exist in a society that thrives on rewarding individualism.

In the example sentence above, the portion after the dash reiterates the point stated earlier while elaborating a bit more on the same. Not only does it tell you more about the concept of altruism, as perceived by the author, but also about the whole statement made earlier. This is very similar to how the dash has been used in the correct choice of the question referred to by you in your post.

Of course, the above question does not limit the universe of the uses of this punctuation mark. You can also use the dash in various other forms, but the idea remains the same: to separate parts of the sentence while adding information. To enhance your understanding, you could refer to some other OG questions in your research - OG 13: Q#98 & Q#132.

Hope that helps!

Regards,
Neeti.
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Last edited by egmat on 28 Apr 2014, 00:06, edited 1 time in total.

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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29 Apr 2014, 08:28
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kinjiGC wrote:
egmat wrote:
kinjiGC wrote:
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.

(A) at some time in the past our ancestors suffered an event, greatly reducing their numbers
(B) that at some time in the past our ancestors suffered an event that greatly reduced their numbers
(C) that some time in the past our ancestors suffered an event so that their numbers were greatly reduced,
(D) some time in the past our ancestors suffered an event from which their numbers were greatly reduced
(E) some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,

Meaning: Some anthropologists believe that the genetic homogeneity evident in the world's people is the result of a "population bottleneck". Population bottleneck – an event that occurred sometime back in the past which greatly reduced their numbers and thus our genetic variation.

Option A) “greatly reducing their numbers” – Verb-ing modifier comma separated, so presenting (modifying) more information about the preceding clause “at some time in the past our ancestors suffered an event” which is incorrect as the event reduced their numbers.

Option C) so that presents reason which is incorrect.

Option D) “from which” is incorrect. The correct sentence would be “some time in the past our ancestors suffered an event that greatly reduced their numbers”.

Option E) “so as” provides an intent.

My confusion is “that” in Option B)
that should replace “population bottleneck”
So the sentence becomes “population bottleneck at some time in the past our ancestors suffered an event that greatly reduced their numbers” – doesn’t look correct to me.

I know after the hyphen “-” the modifier comes which provides more information about the preceding noun.

Dear Kinjal,

The punctuation mark referred to by you is technically called a “dash”. Yes, it has a slightly less fancy name than the “hyphen”.

Moving on, the dash can be used in multiple ways. In the sentence at hand, it has been used to establish more on what the author has mentioned before the dash. If you observe, the portion after the dash not only expands on the “bottleneck” bit but also on how the genetic homogeneity is the result of the mentioned bottleneck. Accordingly, if I were to draw a parallel structure it would be something on the following lines:

Mariana believes that altruism exists even in today’s day and age — that people can help others without any selfish motives is not an idea that is too unrealistic to exist in a society that thrives on rewarding individualism.

In the example sentence above, the portion after the dash reiterates the point stated earlier while elaborating a bit more on the same. Not only does it tell you more about the concept of altruism, as perceived by the author, but also about the whole statement made earlier. This is very similar to how the dash has been used in the correct choice of the question referred to by you in your post.

Of course, the above question does not limit the universe of the uses of this punctuation mark. You can also use the dash in various other forms, but the idea remains the same: to separate parts of the sentence while adding information. To enhance your understanding, you could refer to some other OG questions in your research - OG 13: Q#98 & Q#132.

Hope that helps!

Regards,
Neeti.

Mariana believes that altruism exists even in today’s day and age — that people can help others without any selfish motives is not an idea that is too unrealistic to exist in a society that thrives on rewarding individualism.

1) The sentence after the hyphen modifies "altruism" but also the author adds more information. So "altruism" need not be close to the hyphen as possible. One of the rule which comes to my mind was usage of Noun+Noun modifier. It is very versatile in the application because it can modify any part of the sentence and also modify the whole preceding phrase. Can you please confirm if same is the case with hyphen usage.
2) The reason why I am asking you is because, in OG 13 Question # 138 - Correct Option
"Although heirloom tomatoes, grown from seeds saved during the previous year, appear less appetizing than most of their round and red supermarket cousinsthey are often green and striped, or have plenty of bumps and bruises—heirlooms are more flavorful and thus in increasing demand."
The noun is closest to the hyphen.
OG 13 Question # 98 - Correct Option.
"Ranked as one of the most important of Europe's young playwrights, Franz Xaver Kroetz has written 40 plays; his workstranslated into more than 30 languages—are produced more often than those of any other contemporary German dramatist.
The noun is closest to the hyphen.

Dear Kinjal,

Since you have cited your analysis for the mentioned two official questions to raise a query about the example sentence, let me address your analysis first:

in OG 13 Question # 138 - Correct Option
"Although heirloom tomatoes, grown from seeds saved during the previous year, appear less appetizing than most of their round and red supermarket cousins—they are often green and striped, or have plenty of bumps and bruises—heirlooms are more flavorful and thus in increasing demand."
The noun is closest to the hyphen.

Per your analysis, the portion between the two dashes — they are often green and striped, or have plenty of bumps and bruises— modifies red supermarket cousins. My question is does this modification make logical sense? If we take this modification in to consideration, we are effectively saying that the comparatively appealing, red supermarket cousins are:
1. green and striped
2. and have plenty of bumps and bruises

Please reconsider the structure of the sentence, keeping in mind the logical meaning that the author wants to convey. I am sure you’ll be able to see the role dash plays in this sentence and the example sentence then.

OG 13 Question # 98 - Correct Option.
"Ranked as one of the most important of Europe's young playwrights, Franz Xaver Kroetz has written 40 plays; his works—translated into more than 30 languages—are produced more often than those of any other contemporary German dramatist.
The noun is closest to the hyphen.

In the above sentence, the purpose of the author is indeed to modify “his works” and this is the precise reason that the author has inserted the modifier here. There is nothing else before the dash here (taking in to account only the portion after the semi-colon). So, the point about the noun being closest to the dash is not relevant in this case.

In all, as pointed to you in my earlier post, the idea behind using the dash is the same: separating parts of a sentence while adding more information.

Hope the above discussion helps!

Regards,

Neeti.
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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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10 May 2016, 09:43
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NoHalfMeasures wrote:
ccooley : I was wondering if you could help me with the following doubts?
1) I am having a hard time understanding how A break the parallelism and why is 'that' required to maintain it. I am referring to OG explanation here.
2) How would you define grammatically what role is dash playing here? I researched use of dash as per grammar rules but didnt find any other example similar to this question.
Thanks

1. The author requires to convey that the fact that "at some time in the past our ancestors suffered an event that greatly reduced their numbers..." is believed by "some anthropologists". Without "that", the sense would be as though the author is expressing his own belief , not the anthropologists' belief.

2. Dash is versatile in use and can play the role of a comma, semicolon or a colon. Dash here plays the role of a colon(:) - the colon can be used to provide further explanation for what comes before it. The dash, as a replacement of a colon, plays the same role here.

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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21 Jun 2016, 13:21
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debbiem wrote:
daagh wrote:
A at some time in the past our ancestors suffered an event, greatly reducing their numbers ------ A hyphen is not the tool to connect two ICs.
B that at some time in the past our ancestors suffered an event that greatly reduced their numbers -------- ‘that ’ is the right connector ---correct choice.
C that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced ------- altered notion; it looks as if the ancestors suffered a calamity in order to reduce their numbers.
D some time in the past our ancestors suffered an event from which their numbers were greatly reduced -------- conjugation of two ICs with hyphenation is wrong.
E some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly, ------ same as in D

Dear Sir,

Is the main reason of choosing b/w B and D is that D has hypen in between and not a semi colon..?
Had there been a semicolon would both B and D be equally correct..?

A hyphen (dash) can be used in place of semicolon - hyphen is a versatile punctuation and can replace comma, semicolon or colon. Hence punctuation is NOT the reason that D is wrong. Following is a reason why A, D, and E (choices without "that") are wrong:

some-anthropologists-believe-that-the-genetic-homogeneity-134793-20.html#p1681019

Moreover "event from which" is not correct usage.

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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11 Sep 2016, 09:59
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iMyself wrote:
macjas wrote:
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.

A at some time in the past our ancestors suffered an event, greatly reducing their numbers
B that at some time in the past our ancestors suffered an event that greatly reduced their numbers
C that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced
D some time in the past our ancestors suffered an event from which their numbers were greatly reduced
E some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,

In the question, I can't understand WHY A is wrong? In A, didn't 'event' modify '' greatly reducing their numbers''?
In B, their indicates what? does it indicate ''anthropologists'', "people" or "ancestors
also, HOW an 'event' greatly reduced their number?
If I say:
They killed their father. [/i] Here, their is the pronoun of they. So, in the sentence B, .....event reduced their number. Here, their is plural but event is singular. I should not say that He killed their father. How the sentence matched its pronoun in B?
Thanks...

1. Following is the official explanation for A:
The omission of that after the dash makes the function of the final clause unclear. The structure makes that clause appear to be an awkward and rhetorically puzzling separate assertion that the writer has appended to the prior claim about what the anthropologists believe. The agent or cause of reducing is unclear.

2. I do not understand your query "HOW an 'event' greatly reduced their number?" Why do you think that an event cannot reduce their number?

3. This query is also not clear - why do you consider that " He killed their father" is not correct? Why only "they" can kill their father and a single person (or a single event) can't?

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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10 May 2017, 01:18
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The Official Guide for GMAT Review 2017

Practice Question
Question No.: SC 736
Page: 695

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.

A at some time in the past our ancestors suffered an event, greatly reducing their numbers
B that at some time in the past our ancestors suffered an event that greatly reduced their numbers
C that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced
D some time in the past our ancestors suffered an event from which their numbers were greatly reduced
E some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,

Attachments

sc736.jpg [ 1.14 MiB | Viewed 833 times ]

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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25 Sep 2012, 10:27
ChrisLele wrote:
In answer choice (A) there is a problem with modification. (A) is implying that our ancestors greatly reduced their own numbers (this is incorrect because it was the event that greatly reduced ancestors). When we have an independent clause followed by a participle phrase (one that starts with a gerund and serves as an adjective clause), the participle phrase modifies the subject of the sentence.

In non-grammarese: 'ancestors' is the subject of the independent clause, 'at some time...' and because of the comma after event, we have the incorrect meaning. It was not the ancestors but an event that 'reduced their numbers.'

Therefore, we want to make sure that it is clear that 'event' is 'greatly reducing the numbers.' One way to fix that is by using the relative pronoun 'that.' In (B), we have 'an event that greatly reduced their numbers' that does a good job of correcting the error in (A).

Use of 'that' in 'that greatly reduced their numbers" sounds good as you explained but how's the use of 'that' in "that at some time in the past.." justified. Please explain.
If "that at some time in the past.." were parallel to "that the genetic homogeneity..", shouldn't the sentence rather look like:
Some people believe that X and that Y.
The sentence as it looks to me actually is like this:
Some people believe something population bottleneck - definition of population bottleneck.

I rejected option B because 'that' in 'that at some time in the past...' sounded awkward and I got the question wrong

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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18 Apr 2013, 00:49
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Thanks a Lot PUNEETSCHDV U saved my day... this is the best explanation of the question available....

There are two pending items that need to be discussed in detail.
Usage of '--' and ' at some time'

Can some guru confirm if below points are correct:

some time: Unspecific time . I want to visit chicago sometime this year
At some time in the past : during some indefinite time in the past
at sometime in the past: same as above
some time: some is an adjective referring to time, quite a while
I’ve been spending some time thinking about income inequality for a piece I’m writing.
sometimes : occasionally

some time in the past -> is wrong ??

Regarding usage of '--':
Check the below link from grockit:
http://grockit.com/blog/gmat/2011/08/01/gmat-sentence-corrections-colons-and-dashes/
So if i interpret it correctly 'DASH'es quite flexible, so "-that at some time in the past " is same as "-at some time in the past"...
can some one confirm this..
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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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09 May 2013, 22:32
ChrisLele wrote:
In answer choice (A) there is a problem with modification. (A) is implying that our ancestors greatly reduced their own numbers (this is incorrect because it was the event that greatly reduced ancestors). When we have an independent clause followed by a participle phrase (one that starts with a gerund and serves as an adjective clause), the participle phrase modifies the subject of the sentence.

In non-grammarese: 'ancestors' is the subject of the independent clause, 'at some time...' and because of the comma after event, we have the incorrect meaning. It was not the ancestors but an event that 'reduced their numbers.'

Therefore, we want to make sure that it is clear that 'event' is 'greatly reducing the numbers.' One way to fix that is by using the relative pronoun 'that.' In (B), we have 'an event that greatly reduced their numbers' that does a good job of correcting the error in (A).

-ING can be used as

(1). Progressive tense : Rita is PLAYING
(2). Gerund: SWIMMING is a good exercise
(3). Adjective: The CAT SLEEPING on the mat is ill
(4). Adverb: Rita failed in the exam,forcing her to commit suicide

In the sentence (4). -ING is used as an adverb which adds to VERB "Failed" an Action.Moreover, there lies no confusion between "Ancestors" or "event" as to what -ING is referring to.However, the problem here is solely with the "SUFFERING".

SUFFERING never caused => reducing in number

"which" would have been appropriate here.

Rgds,
TGC
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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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10 May 2013, 07:16
Sure no problem; when I had requested:

Can you see if you can post an official example where above kind of construct is valid.

By official example I meant questions from Official guides, GMATPreps etc. (these are called "official sources"), not MGMAT guides.
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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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23 Dec 2013, 23:29
This question can be solved by identifying two easy splits:
- Believe X - Believe X: the two X's should be parallel - "That the genetic..." should be parallel with " that at some time..."
Eliminate A, D & E
- "at some time" vs. "some time": we require a definite period of time, at some time answers the question "when? at some time"; A would have been correct if we had "sometime" instead of "some time"
Eliminate C

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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24 Mar 2014, 09:08
macjas wrote:
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.

A at some time in the past our ancestors suffered an event, greatly reducing their numbers
B that at some time in the past our ancestors suffered an event that greatly reduced their numbers
C that sometime in the past our ancestors suffered an event so that their numbers were greatly reduced
D some time in the past our ancestors suffered an event from which their numbers were greatly reduced
E some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,

This sentence have two error 1) Hypen - Always add additional information but here its not
2) Greatly reducing ... is not modifying the previous class or its the results of previous clause

For modifiers to make sense it should associate with the subject of the preceding clause which is "Ancestors". Ancestors is not the doer of the action suffered so in the modifier sentence "reducing " which is Ancestors suffered an event and thus they greatly reduced their number. This does not make sense.

So there should not be modifier in the sentence.
Hence B is correct

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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07 Apr 2014, 23:50
B, the correct answer, seems to be much more parallel than D. B has a structure:

our ancestors suffered an event that greatly reduced X (their numbers) and Y (our genetic variation)

D says:

our ancestors suffered an event from which their numbers were greatly reduced and and thus our genetic variation.

The only way to intepret this logically is:

our ancestors suffered an event from which their numbers were greatly reduced and and thus our genetic variation (was greatly reduced).

Also notice that D is a passive voice construction ("their numbers were greatly reduced ..."). Generally if an active voice construction is present, it should be preferred.

Also, "at" seems to be missing in D ("at" some time in the past..).

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Re: Some anthropologists believe that the genetic homogeneity [#permalink]

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20 Apr 2014, 11:03
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.

(A) at some time in the past our ancestors suffered an event, greatly reducing their numbers
(B) that at some time in the past our ancestors suffered an event that greatly reduced their numbers
(C) that some time in the past our ancestors suffered an event so that their numbers were greatly reduced,
(D) some time in the past our ancestors suffered an event from which their numbers were greatly reduced
(E) some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,

Meaning: Some anthropologists believe that the genetic homogeneity evident in the world's people is the result of a "population bottleneck". Population bottleneck – an event that occurred sometime back in the past which greatly reduced their numbers and thus our genetic variation.

Option A) “greatly reducing their numbers” – Verb-ing modifier comma separated, so presenting (modifying) more information about the preceding clause “at some time in the past our ancestors suffered an event” which is incorrect as the event reduced their numbers.

Option C) so that presents reason which is incorrect.

Option D) “from which” is incorrect. The correct sentence would be “some time in the past our ancestors suffered an event that greatly reduced their numbers”.

Option E) “so as” provides an intent.

My confusion is “that” in Option B)
that should replace “population bottleneck”
So the sentence becomes “population bottleneck at some time in the past our ancestors suffered an event that greatly reduced their numbers” – doesn’t look correct to me.

I know after the hyphen “-” the modifier comes which provides more information about the preceding noun.

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Re: Some anthropologists believe that the genetic homogeneity   [#permalink] 20 Apr 2014, 11:03

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