Either food scarcity or excessive hunting can threaten a population of

Question

Which of the following most logically completes the reasoning?

Either food scarcity or excessive hunting can threaten a population of animals. If the group faces food scarcity, individuals in the group will reach reproductive maturity later than otherwise. If the group faces excessive hunting, individuals that reach reproductive maturity earlier will come to predominate. Therefore, it should be possible to determine whether prehistoric mastodons became extinct because of food scarcity or human hunting, since there are fossilized mastodon remains from both before and after mastodon populations declined, and __________.

(A) there are more fossilized mastodon remains from the period before mastodon populations began to decline than from after that period

(B) the average age at which mastodons from a given period reach reproductive maturity can be established from their fossilized remains

(C) it can be accurately estimated from fossilized remains when mastodons became extinct

(D) it is not known when humans first began hunting mastodons

(E) climate changes may have gradually reduced the food available to mastodons

ID: 500263

Hussain15 · Answer

Hi HBS, welcome the club!!

Find my comments in colors below.

So, IMO "B"

whamberto · Answer

I have chosen the answer B for this question:

A. This answer choice only states the obvious assumption. Also, this statement does not help us identify whether the mastodon's became extinct because of food scarcity or excessive hunting.

B. This is the correct answer. By knowing the average age of reproductive maturity of the fossils, you can identify whether the fossils are in the "early stages" or whether they are in the "late stages." This will essentially tell you how the mastodon's became extinct - food scarcity or excessive hunting.

C. This answer choice tells us nothing. However, if the fossils were before the time of "hunting," then we could assume that the mastodons became extinct because of food scarcity.

D. Since it is not known when humans began hunting, this answer choice cannot be correct.

E. The fact that climate changes "may have" caused scarcity indicates some uncertainty. Also, it doesn't give us any additional information about the fossils.

nitestr · Answer

One way I find you can resolve this kind of questions which doesn't show direct flow is to sketch simple diagram

species ->hunted
 |
 early rep.

species -> less food
 |
 late rep.

this helps me not to re-read the premise again & waste time / get confused

Abhishek009 · Answer

Food scarcity --------> Late reproductive maturity Excessive hunting---> Early reproductive maturity Untitled.png Determination of the possible cause of extinction of prehistoric mastodons if possible only only when - 1. We have fossil remains of mastodons 2. We can compare the age reproductive maturity Thus among the given options only (B) matches, and is the correct answer..

aragonn · Answer

Premise : 
-Food scarcity or excessive hunting can threaten a population of animals 
-Food scarcity: individuals will reach reproductive maturity LATER than OTHERWISE 
-Excessive Hunting: individuals who reach reproductive maturity EARLIER will come to predominate.

Conclusion : 
-It should be possible to determine whether mastodons became extinct because of FOOD SCARCITY OR HUMAN HUNTING, since there are fossil remains from before and after mastodon populations declined and ______

Pre-thinking: 
 There appear to be 2 causes that can impact reproductive maturity (food scarcity - leads to LATER maturity; excessive hunting - leads to EARLIER maturity). But earlier or later THAN WHAT? The prompt doesn't establish what the "normal" time is. The prompt concludes that there should be a way to figure out whether mastodons were victims of food scarcity or human hunting though, so I'd be looking for an answer that establishes the "normal" age of maturity of the mastodon. That way, having the fossils will allow us to figure out if they matured earlier or later than normal. 
 (B) the average age at which mastodons from a given period reach reproductive maturity can be established from their fossilized remains ---- this option is on same lines. Correct response.

CAMANISHPARMAR · Answer

Argument Construction

Situation  In a population of animals, food scarcity causes later reproductive maturity; if that population is hunted excessively, earlier-maturing animals will be more numerous in the population.

Reasoning  What point would most logically complete the argument? For the information given to be of use in determining what caused mastodons' extinction, mastodon fossils would need to indicate the age at which mastodons reached reproductive maturity, since that is what the argument suggests can indicate cause of extinction. If fossilized remains exist from before and after mastodon populations began to decline, and if the age at which those fossilized mastodons reached reproductive maturity can be determined, then we will have a good idea of what caused their extinction: if they reached reproductive maturity late, it was probably food scarcity, but if they matured earlier, it was most likely hunting.

Correct answer is option B  This statement properly identifies a point that logically completes the argument: it explains how the fossilized mastodon remains could be used to help determine what caused mastodons' extinction.

EatMyDosa · Answer

GMATNinja ,  VeritasKarishma , @EMPOWERGMAT,  egmat ,  CrackVerbal

I have two basic questions regarding the given argument.

First : In the context of the argument, what does "predominate" mean in the 3rd sentence?

Does it mean that members of an animal group that reach maturity earlier would likely to have more of their offsprings survive excessive-hunting based on sheer numbers compared to offsprings of those members which reach maturity later?

Second : In the context of option B, let's say we can calculate the average maturity age of mastodons from "before" and "after" time period (based on the available fossils) and the average maturity age of both groups of mastodons comes out to be different.

For example: Avg. maturity age ("before" group of mastodons) = 10 years
Avg. maturity age ("after" group of mastodons) = 12 years

Wouldn't it still be possible that the numbers first declined because of excessive hunting and then the remaining mastodons faced food scarcity and died because of it?

If this is possible, then how could we identify or decide on the cause of extinction?

GMATNinja · Answer

Great questions! Your definition of "predominate" is on the right track, but we can probably simplify it. We're dealing with a population of animals and two groups are being compared (animals that reach reproductive maturity earlier vs. animals that reach reproductive maturity later). So "predominate" probably just means something like the majority of the population. Your definition sounds like you're trying to explain  why  excessive hunting would lead to animals that reach reproductive maturity earlier being the majority of the population. But that isn't really important to the argument.

As for your second question, it definitely seems possible that both excessive hunting and food scarcity could play a role. But the argument concludes " it should be possible  to determine whether prehistoric mastodons became extinct  because of food scarcity  or  human hunting ." That sounds like it's probably going to be one or the other -- not a combination of both. Keep in mind that we're looking for the answer choice that " MOST  logically completes the reasoning" -- not the  perfect  answer.

I hope that helps!

KarishmaB · Answer

Two reasons threaten animals - food scarcity or excessive hunting

If food scarcity, individuals in the group will reach reproductive maturity later than otherwise.
If excessive hunting, individuals that reach reproductive maturity earlier will predominate the group.

Therefore, it should be possible to determine whether prehistoric mastodons became extinct because of food scarcity or human hunting, since there are fossilized mastodon remains from both before and after mastodon populations declined, and ...

The argument gives us two reasons that threaten and tells us how the group composition changes in either case.
It concludes that we should be able to determine what the reason was for extinction of mastodons - food scarcity or hunting.
The last part is supporting why we should be able to determine the reason. To determine the reason we would need to know whether after getting afflicted with the cause, the 'individuals in the group reached reproductive maturity later' or 'individuals that reached reproductive maturity earlier predominated'.

We are given that remains from before and after decline are available. Now to determine, we should be able to figure out the age at which they reached reproductive maturity. This is what (B) says:

(B) the average age at which mastodons from a given period reach reproductive maturity can be established from their fossilized remains

The last part now becomes:
... since there are fossilized mastodon remains from both before and after mastodon populations declined, and the average age at which mastodons from a given period reach reproductive maturity can be established from their fossilized remains.

Perfect. Now we can find out the reason for extinction.

Answer (B)

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