it actually undermines Marco's argument.
1. Marco says Kangaroos fed mainly on shrubs. 2. Shrubs feel fine when climate is arid. 3. Climate was getting more arid when GK went extinct.
Option A says THE OPPOSITE: the climate was getting LESS arid at the time kangaroos went extinct.
This totally ruins Marco's point. It might mean, shrubs became less available during that time, and the GK actually died out from hunger.
Hi
aakash214. Thanks for posting this here.
I came across this question on GMAT Prep took and took a long time struggling with it before figuring it out. It is definitely one of the harder ones I have come across!
Firstly let's list down what each of them is saying:
Quote:
Marco: Giant kangaroos - one of several extinct species of large mammals (megafauna) - went extinct around 46,000 years ago. The deposits and wear patterns on the teeth of these animals from around the time of their extinction indicate that they fed mostly on saltbrush shrubs. Saltbrush thrives in arid climates, so it is not likely that the kangaroos' food supply was adversely affected by the increasing aridity of the climate at that time. Thus, something else would have to account for their extinction, and the best candidate for that cause is predation by humans.
- GKs are one of many species of large mammals
- Went extinct 46,000 years ago
- Evidence from from teeth show they fed mostly on saltbrush
- Saltbrush thrives in arid climates
- We know climate was becoming more arid at the time
- The aridity will help heir main food thrive
- The aridity should in fact help the species thrive, because their main food source will thrive NOT make them extinct
- Hence if it wasn't the climate it HAD to be something else and humans are the most likely.
Quote:
Fatima: That argument alone is not likely to satisfy many researchers in this field. Have you found any other evidence to bolster your conclusion ?
- This argument alone is not enough to convince researchers of your conclusion
- Is there any other evidence you have to support your claim?
So Marco lists down a bunch of facts about GKs, their habitats and the climate of the time they lived and concludes that increasing aridity of the time means that external factors such as humans were responsible for GK's extinction. Fatima is largely skeptical of the tall claims and asks for more evidence.
Questions asks:
Select Marco for the statement that, if true, most justifies Marco’s assertions, and select Fatima, for the statement that, if true, most justifies Fatima’s skepticism about Marco’s assertions. Make only two selections, one in each column.So we are looking for facts that SUPPORT Marco's and Fatima's assertions (one option each), choices are:
Quote:
A) Giant kangaroos became extinct during a period that was less arid than previous periods they endured.
Yes! Marco does note that the climate, at the time the GKs went extinct, was becoming increasingly arid and dry. It was not the main crux of the arguement but was part of the evidence used to support the conclusion for sure. Lets hold on to this for now as a candidate supporting Marco's assertion.
Quote:
B)Many researchers believe humans first arrived in Australia around 40,000 years ago.
This is a perfect candidate for a fact that supports Fatima's skepticism, if humans arrived only 40 thousand years ago they could not possibly have been the cause of GK extinction 46 thousand years ago! Seems like a good match for Fatima!
Quote:
C)Approximately 60 different species in Australia died out in the wave of extinctions around 46,000 years ago.
Does not help support either of the people's arguments.
Quote:
D)Fossils of giant kangaroos also show evidence that those animals' diets routinely included plants other than saltbrush.
This is actually irrelevant to what Marco has to say, simply because Marco says that their main diet saltbrush was in ample supply and only becoming more widely available due to the increasing aridity of the climate. If GKs did indeed eat something else as well, it really does not support Marco because he has already concluded based on available evidence that their main food source was in ample supply.
Quote:
E)Several types of megafauna larger than the giant kangaroo went extinct around 46,000 years ago.
Extinction of other larger megafauna are not relevant to either of their discussions.
You will see that once you rule out the improbable and unrelated choices only A and B match with Marco's and Fatima's assertions respectively.
Hope this helps. I can't say for sure but this seems like one of the harder IR Qs. I got it wrong too when I was taking the practice test myself.