#13 - The size of northern fur seals provides a reliable

[Administrator]

Complete Question Explanation

Must Be True. The correct answer choice is (E)

Based on the average body size of a northern fur seal it is possible to reliably determine the species’
local population levels; larger populations correlate with a smaller average body size. Archeologists
researched an 800-year period during which the seals were hunted by North American natives, and
found that the average body size of the seals remained fairly stable. The stability of the average body
size of the seals would indicate that the fur seal population remained fairly stable during that period
as well.

The question that follows is a Must Be True question, so the correct answer choice will be supported
by the information provided in the stimulus.

Answer choice (A): The information in the stimulus suggests that the seal populations were not
significantly depleted by the hunting of North Americans during the 800-year period studied, but
there is no information about the degree of variety in hunting practices among different groups of
Natives at that time.

Answer choice (B): The author makes no mention of the correlation between the body weight of the
northern fur seals and their overall health, so this choice fails the Fact Test and can be ruled out of
contention.

Answer choice (C): Although there was not much fluctuation in the seals’ average weight during the
800-year period studied, that does not mean that there was fluctuation before that period. Since there
is nothing in the stimulus to support this assertion, it cannot be the right answer to this Must Be True
question.

Answer choice (D): The stimulus does lead to the inference that the fur seal population was not
significantly depleted during the 800-year period studied, but this was not necessarily the result of
any intent on the part of the Native peoples. Since the author provides no information about any
such efforts on the part of the Natives during that time, this choice cannot be confirmed by the
information provided in the stimulus.

Answer choice (E): This is the correct answer choice. As discussed, the fact that the average
body size of the seals did not vary significantly suggests that the seal population levels did not vary
significantly either, meaning that the population could not have been significantly depleted by the
hunting of the north Americans during the 800-year period under examination.

[Tony_Stark]

Hi, I have a question about this. I do see the flaws in A - D, however, I am wondering about something in E.

The stimulus says, "The size of northern fur seals provides a reliable indication of their population levels" then it goes on to establish the relationship by saying: the smaller the size of seals, the larger the population.

Decrease Body Size Increase Population.

The stimulus then goes on to say that the size did not vary much in the 800 years. From this, how do we know that the population did not go DOWN? I thought that we can only guarantee that the population did not go up.

Thanks!

[Jonathan Evans]

Hey Tony,

Excellent question and good job coming up with a conditional. However, the conditional actually does not just go in one direction here! We have an inversely proportional relationship between the size of the seals and the size of the population.

In other words, as one goes up, the other goes down. This works both ways:

• More seals Smaller seal size
  Fewer seals Bigger seal size

How do we know this is the case and not just the one directional conditional? Part of it is idiomatic: the plain meaning of this construction—"the bigger they are, the harder they fall"—implies a reciprocal relationship between the two quantities. We also know this relationship goes both ways from the first part of the sentence: "The size [...] provides a reliable indication of their population."

Thus, we actually have sufficient evidence for (E)! Further, note the nuance in the question stem itself: "the statements if true provide the most support for..."

By this standard, (E) clearly meets the bar. Good question!

[ray57]

Hello,

I chose A for this one because in the stimulus it says that the body size of the seals did not vary significantly so I thought that it meant that the hunters did not have different practices, or else the seals would be different sizes depending on the region. So I thought A was correct since it says just that--that hunting didn't vary, so seal body size didn't vary.


Also, since E is correct because the hunters did not "overhunt" the seals, could another (hypothetical) correct answer choice have been if the hunters "underhunted"?

Thanks for your help.

[Jeremy Press]

Hi ray57,

Great question!

With answer choice A, I see a couple problems with your reading. First, you're bringing additional information in to the question in order to shade your interpretation of the answer choice. You're importing the idea that different hunting practices would necessarily lead to different sizes of seal populations (and therefore different seal body sizes). But that causal chain isn't necessarily true, and the stimulus doesn't give us any basis for deciding whether it is, in fact, true. Therefore, we can't make the connection you're making there. But, and this is getting a little more nuanced, even if it were true that different hunting practices led to different population outcomes and different body sizes in different regions of North America, it would still be possible that the overall average body size of seals across North America didn't change during the period in question. Thus, answer choice A would not HAVE to be true based on the information provided.

With answer choice E, you're absolutely right to note that the answer could have been stated the other way, that the hunting practices did not significant "increase" the northern fur seal population (since body size and population are inversely proportional). The wording of the answer is likely a result of the test writers' desire to match the natural assumption test takers would make about hunting, that, by eliminating population members, it (considered by itself) will have a tendency to reduce populations (a tendency that nevertheless didn't manifest in this situation, which we know from the data about body size).

I hope this helps!

Jeremy