Some anthropologists argue that the human species could not have survived prehistoric
times if the species had not evolved the ability to cope with diverse natural environments.
However, there is considerable evidence that Australopithecus afarensis, a prehistoric
species related to early humans, also thrived in a diverse area of environments, but became
Hence, the anthropologists' claim is false.
So argument or facts?
Clearly, we have an argument.
'Hence' will be our structural indicator the conclusion being the anthropologists' claim
What was this anthropologists' claim?
You notice, the first sentence tells us some anthropologists argue that human species could
not have survived prehistoric times if the species had not evolved the ability to cope
with the diverse natural environments.
We know 'if' introduces sufficient, so not evolved the ability to cope with diverse
Then the necessary condition would be, could not have survived prehistoric times, so survived
prehistoric times negated.
The contrapositive would tell us that to survive prehistoric times they must evolve the ability
to cope with the diverse natural environments.
So that is the anthropologists' claim, you notice it is a general principle.
And then, the author gives us a premise that he believes disproves this general principle,
and that is the example of Australopithecus afarensis, a prehistoric species related to
early humans that also thrived in a diverse array of environments, but became extinct.
So basically, Australopithecus afarensis had the ability to survive in diverse array of
environments, so evolved the ability to cope in diverse array of environments and also
tells us that they became extinct, so they did not survive prehistoric times.
And takes that to conclude, therefore the anthropologists' claims is false.
So let's take a closer look.
The anthropologists claim here is a sufficient and necessary statement.
How do we disprove a sufficient and necessary statement?
Well, imagine that I told you that all berries are red, how would you prove me wrong?
You would show me a blueberry.
Maybe a boysenberry, right?
An idea there is you would be showing me a berry that is not red.
So to disprove a sufficient and necessary statement, you want to show sufficient can
exist without necessary.
So in order for this author to correctly disprove this anthropologists' statement, he would
have to show either a creature that survived prehistoric times, but that did not evolve
the ability to cope with diverse natural environments.
Or, a creature that did not evolve the ability to cope with diverse natural environments,
but survived prehistoric times.
And you notice the example of the Australopithecus afarensis, shows us neither of those.
Instead you see a species that has evolved the capacity to deal with a diverse array
of natural environments, but that did not survive prehistoric times.
And you notice, based on the principle having evolved the ability to cope with a diverse
array of natural environments is our necessary condition.
It tells us nothing about whether this species has survived or not survived prehistoric times.
We cannot go backwards, don't just reverse!
So you notice here, the author is assuming that the general principle is the reverse.
That if we have evolved the ability to cope with diverse natural environments, then we
survive prehistoric times.
Because the example of Australopithecus afarensis shows us evolved the ability to cope with
diverse natural environments, but did not survive natural prehistoric times and that
would be correct then because we would be showing sufficient without necessary.
But again, it's not correct because that is not what the anthropologists are claiming,
they're claiming the reverse of that, so clearly we have a flawed argument.
And now that we have a clear understanding of this mistake, again, the author is reversing
or mistaking sufficient for necessary.
So the reasoning in the argument is most vulnerable to criticism, on the grounds that the argument
most vulnerable to criticism we have an Errors in Reasoning question.
So we've identified the error, don't just negate or mistaking sufficient from necessary
so let's go find the answer choice that explains that flaw.
(A) confuses a condition being required for a given result to occur in one case with a
condition being sufficient for such a result to occur in a similar case.
You notice confusing what is required for what is sufficient mistaking sufficient
for necessary which is exactly what we saw in the passage, so (A) would be the correct
Again, because to disprove sufficient and necessary, you must show sufficient without
This case, the author showed us necessary without sufficient and that is not correct.
We know nothing about sufficient based on whether or not necessary is present.
So the author is clearly reversing this statement assuming that it said the reverse, because
then his evidence would have shown sufficient without necessary and would've disproved the
anthropologists' claim if this was their claim but it's not.
So again you notice the mistake here is they are reversing sufficient and necessary conditions.
So (A) would be the correct answer.
But again let's just make sure.
(B) takes for granted that if one species had a characteristic that happened to enable
it to survive certain conditions, at least one related extinct species must have had
the same characteristic.
You notice that's clearly not happening in this passage.
That is not the assumption, it is not taking that for granted.
So (B) would be out.
(C) generalizes from the fact that one species with a certain characteristic survive certain
conditions that all related species with the same characteristic must have survived exactly
the same conditions.
And actually the author is not doing that at all because they showed us a related species,
Australopithecus afarensis that did not survive prehistoric times.
So, (C) clearly does not apply and (C) would be eliminated.
(D) fails to consider the possibility that Australopithecus afarensis had one or more
characteristics that lessens its chances of surviving prehistoric times and that is clearly
not what's going on.
That is true, but it's not the flaw.
The problem here is that the anthropologist's general principle is not refuted by the author's
evidence because the author's evidence would only refute the reverse of the anthropologists'
claim so that's the problem.
(D), you could argue it's true he does do that but that's not the logical flaw, so do
not pick it as the correct answer.
Moving to (E), fails to consider the possibility that even if a condition caused the result
to occur in one case, it was not necessary to cause the result to occur in a similar
case and again clearly out.
This is not a cause and effect argument, so how can (E) be the correct answer?