Some anthropologists believe that the genetic homogeneity evident in

Hi GMATNinja generis GMATNinjaTwo

Can you help to differentiate between function of a hyphen and semicolon?

Hello Arpit @adikikani,

I will be glad to help you out with this one.


To begin with, this official sentence uses a dash and not a hyphen.

Now generally, both hyphens and semi-colons are used to connect two independent clauses.

However, in the correct answer choice of this official question, the hyphen is followed by a dependent clause.

Personally, I see this usage just as an exception to the rule, an atypical usage in a one-off case.


Hope this helps.
Thanks.
Shraddha

egmat

1. I understand that "that" is needed after the "-" in order to maintain the parallelism between " that the genetic homogeneity evident in the world's people is the result of a "population bottleneck" and "that at some time in the past our ancestors suffered an event" as the portion after the "-" simply elaborates the portion before "-" and adds some more information. Please tell me if my understanding is correct.

2. However, please explain why is ", greatly reducing their numbers" wrong as I understand that ",-ing" modifies the preceeding clause and either presents the result of the action done in the preceeding clause or describes how the action is being done in the preceeding clause. Here, we can see that "greatly reducing their numbers" clearly presents the result of "past our ancestors suffered an event". Please explain

Hello aviejay,

Thank you for the query and the PM.


1. Yes, your understanding is correct.

2. It is true that the comma + verb-ing modifier presents either the how aspect or the result of the modified action. However, in modifying the preceding action, the comma + verb-ing modifier must also make sense with the doer of the modified action.

You are correct in saying that that comma + verb-ing modifier reducing seems to present the result of the action suffered. But, comma + reducing fails to make sense with doer - our ancestors - of the modified action.

Choice A seems to suggest that our ancestors suffered an event and as a result reduced their numbers. This meaning is certainly not logical.

From the context of the sentence, we know that the event that our ancestors suffered reduced their numbers.


Hope this helps.
Thanks.
Shraddha

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:

Reducing : Is the action is still continuing (NO). So this is wrong. it reduced long back.

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

Correct answer: That (refer to the genetic homogeneity evident in the world's people is the result of a "population bottleneck")
2. suffered an event that greatly: So the event that is greatly reduces the number

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

so that their numbers were greatly: using of so that is wrong. No one forcibly reduced the number. As one event happened which reduced the number. So WRONG

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

their numbers were greatly reduced: seems like someone reduced their number.WRONG

(E) some time in the past, that our ancestors suffered an event so as to reduce their numbers greatly,

so as to reduce their numbers greatly,: It seems like the ancestors only reduced their number. WRONG

Can we reject option A because we are joining 2 independent clauses using —(dash) ?

Also, I understand that in option 'A', it does not makes sense that the doer of the actions, 'suffered an event' and 'greatly reducing their numbers', is 'our ancestors' even though the 2nd action is clearly a result of the first.

Please correct me if I am wrong

Thanks
Saurabh

Hi Sarjaria84,

Although some people feel that a dash should not be used to join two independent clauses, I don't think we should regard that as a (reliable) rule. The GMAT doesn't really test punctuation all that much, so we'd be taking a risk if we were to apply something like that.

We could instead remove A because it drops the that that is supposed to describe ("limit") an event:
... our ancestors suffered an event... ← This doesn't make any sense. What kind of event? We would never say something like "they suffered an event" and end the sentence there, without adding anything to event.

I chose option A rather than B on the grounds of verb-ing modifier. In option A verb-ing modifier modifies verb 'suffered" which according to me is right rather than saying that an "event" reduced the numbers of ancestors as in option B.
Can anyone tell me where i went wrong?

The act of suffering wouldn't, by itself, reduce the numbers. So, with choice (A), we are left wondering, "What, exactly, caused the reduction?"

A catastrophic event (i.e. an earthquake, a volcanic eruption, a meteor impact) could certainly kill many people and reduce the numbers of a group.

VeritasKarishma GMATNinja please explain option C and D

Posted from my mobile device

Notice that the sentence ends with "and thus our genetic variation." So we need something that's parallel to the noun "our genetic variation."

In choice (C), "event" wouldn't work (our ancestors didn't suffer our genetic variation!). If we wanted "genetic variation" to be parallel to "their numbers were greatly reduced," we'd need another verb paired with "genetic variation" (as explained in this post).

The parallelism is off in (C), so it can be eliminated. A similar analysis applies to choice (D).

I hope that helps!

I thought I read in my book that what comes before and after a semicolon (;), the two dots (:), and an em dash (-), both have to be able to stand alone as a sentence. Starting with 'that' at the beginning of the sentence neglects that point.

Therefor I neglected (A) and (C) from the beginning since they started with 'that'.

Hi ldlefebvre,

One way to use a semicolon is to place it in between two related independent clauses. Similarly, we can use a dash in between two independent clauses, but that doesn't mean that we can't use those punctuation marks in other ways. Also, we may see a that at the beginning of an independent clause (because that can be used in multiple ways).

GMATNinja

Is the -ing modifier "greatly reducing" really a make-or-break issue here?
I think, present participles can be used as verb modifiers and as noun modifiers. In this case, if one assumes that "greatly reducing" is a verb modifier, then it has to be logically connected to the subject of the main clause, namely "our ancestors". But this connection is, as already mentioned, illogical.

If one assumes that "greatly reducing" modifies the preceding noun "event", then this meaning issue is resolved. And I think it is actually grammatically correct.
Example: "Charles fed some chocolate to the neighbor's cat, sleeping on the rug"
I don't think you are sleeping on the rug, are you?

Maybe I am missing something. Can you please help me out with this?

Hello Chris

I understand your reasoning, but I read that particular option in a different manner- let me explain.

|At some time in the past (modifier)| our ancestors suffered an event (S-V), greatly reducing their numbers (Cause-effect)

Am I completely in the wrong here?


Regards
NikhilST

Hi NikhilST, when you say Cause-effect, I am assuming you mean:

i) Cause: our ancestors suffered an event

ii) Effect: greatly reducing their numbers

Since greatly reducing their numbers is a present participial phrase (preceded by a comma), it will modify the subject of the preceding clause, which in this case happens to be our ancestors!

So, the way A is structured, it is nonsensically suggesting that ancestors reduced their own numbers!

p.s. Our book EducationAisle Sentence Correction Nirvana discusses present participial phrases, their application and examples in significant detail. If you or someone is interested, PM me your email-id; I can mail the corresponding section.

You're right that -ing modifiers can describe either nouns or full clauses, but context will usually make it clear how the -ing should operate. Consider two examples:

1) Tim waved to his toddler, tripping over the strategically positioned cat.

In this case, because "tripping" follows a comma and a full clause, it makes sense to assume that the entire clause is modified. In other words, "tripping" is a consequence of Tim waving to his kid, and it's Tim who is taking a tumble here.

2) Tim waved to his toddler tripping over the strategically positioned cat.

Now, because "tripping" doesn't follow a comma, it seems to modify the noun it's right next to, so it's the toddler who's falling over. (And Tim is callously waving to the kid instead of checking on the little guy.)

In your example, "sleeping" follows a full clause and a comma, so it seems to modify the entire previous clause. But, as you noted, that wouldn't make any sense, as it seems as though Charles is asleep on the rug and, while he's out cold, he's also feeding the neighbor's cat. Can a reader figure out what the writer meant? Eventually, sure. But because the default interpretation is an illogical one, the GMAT wouldn't want a construction like this.

Back to the problem. In (A) we have the following:


Notice that this is more like the first case, in which the "-ing" appears after a comma and a full clause, so most readers will default to assuming that the "-ing" is describing the entire preceding clause, as opposed to modifying the noun "event." If "reducing" is modifying the entire preceding clause, it certainly sounds as though it's the ancient ancestors who are reducing their own numbers. At best, this construction is confusing and requires multiple reads to land on a logical interpretation.

Contrast that construction with (B):


There's only one way to interpret this. "That'" has to refer to "event," and it's the event that's responsible for population decrease.

So rather than agonize over whether (A) is technically wrong, it's enough to see that (B) is clearer, and therefore better.

I hope that helps!