Q6 - A primate jawbone

[WaltGrace1983]

I would like to talk about this question and what I am missing here. I got it right; I was confident; but it still seems unsettling to me during review. Let's go through the question and then I'll talk about my hesitations.

Researchers find an ape jawbone in Namibia, dating back to 10-15 million years ago
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Researchers agree that ancient primates lived only in dense forests
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Namibia, which is now dry and treeless, must have been a forested terrain earlier

There is a lot of good stuff happening here. We have some conditional language with the word "only," telling us that IF an ancient primate lived there THEN it must have been a dense forest. There are two main gaps here:

(1) We also get a little bit of a bias issue when we conclude something that "must have" been true from what a group of researchers "generally agree" upon. Maybe the researchers are wrong?

(2) Also, and perhaps the biggest gap of them all, we get this idea that, because the jawbone was found there, the ape must have lived there! Well maybe that is not exactly true! Maybe the jawbone was brought from miles away from a antelope that picked it up and moved it on its migration route. Maybe it traveled via a river that brought it to Namibia from a land far away. Who knows, right? This gap is probably what the LSAT is going to attack.

(A) "Modern apes?" We don't care about anything that modern apes do. This can be easily eliminated for scope issues.

(C) Perhaps this is true yet perhaps it is not. Either way, we do not need to assume this. The argument is talking solely about an ape that lived around 10-15 million years ago. Who cares about what happens before that? For very similar reasons to (A), we can eliminate this due to scope issues.

(D) This one is talking about diets. To put it plainly, we don't care about diets. The only way that we would care about diets is if it had something to do with where the apes lived but the stimulus would have mentioned something about "diets" if this was a gap. Once again, we can eliminate this one due to scope issues.

(E) Well these answers just get worse and worse. This one can be easily eliminated due to scope issues as well. Now I can see why this answer could be tricky if you really stretch it. Perhaps the apes caused damage to the ecology and this gives us the reasoning why the area is now dry and treeless. There is a problem with this thought process though: we don't care about why the conclusion is the way it is. We only care about why the premises do not justify the conclusion. That is it. Remember the task!

Now here is where my questioning comes in...

(B) is correct because it speaks to gap (2). The argument is concluding that, since the jawbone was found in Namibia and since apes only lived in forests, then it must be true that Namibia used to be a forest. This answer choices tells us that the ape whose jawbone this was lived in or around Namibia. This helps the conclusion by strengthening it but is answer choice really necessary? After all, the ape could have originally lived in Sweden but died in Namibia during its migration to a densely forested space. Thus, it is not necessary for the ape to have lived in - or even around - Namibia.

So my question is this: am I misunderstanding the point of the task? There is no indication that this question is a necessary assumption question but it is in the necessary assumption Cambridge packet. What is going on here?

[mjacob0511]

The argument is reasoning that since the ape lived in or near Namibia and these ancient primates only lived in dense forests --> you can assume that this area used to be a forested terrain.

If you negate B, then the argument falls apart. You're point about "Sweden" works against your reasoning. If the ape lived in Sweden and was merely traveling, then the argument that this area was a forest in those days doesn't follow. Ape's only lived in forest areas, but here it was just traveling. So yes you do need B to be true.