#6 - Prehistoric chimpanzee species used tools similar to

[est15]

I'm not sure why A is incorrect. I feel like the argument assumes that prehistoric humans did not carry their tools with them. If they carried the tools from savannas (where the tools were found) to forests (where the chimpanzees lived), then the chimpanzees could use those tools too. Or if the humans carried the tools from the forests where the chimps were to the savanna where the tools were found, that meant the chimps had been using those tools too. Even if the area where the tools were found was not a forest at the time the tools were in use (answer choice D), I feel like that still doesn't account for the fact that the tools could travel to other forests where chimps live. Could you explain why A is wrong and why D is right?

[Nikki Siclunov]

Hi est15,

I'm afraid you misunderstand the meaning of a necessary assumption - it is a statement that must be true for the conclusion to work, or else the conclusion is false. In this argument, do we really need to assume that prehistoric humans never carried their tools with them? Of course not. Even if they did carry their tools when traveling from one place to another, that does not automatically mean that they carried them from the savanna to the forest, or vice versa. And even if they did, there is no reason to suspect that they either gave them to the chimps in the forest, or took the tools from the chimps. Either way, to conclude that the logical opposite of answer choice (A) weakens the conclusion is a bit of a stretch. Answer choice (A) is therefore not an assumption upon which the conclusion depends. Granted, if (A) were true the conclusion would be somewhat stronger, but that does not mean that answer choice (A) must be true for the conclusion to be logically valid.

By contrast, the logical opposite of answer choice (D) rips the conclusion to shreds. If the area where the tools were found was a forest at the time the tools were in use, and the chimps lived only in forests, then we can no longer be certain that the tools were used by humans: they could have been used by chimps instead. Since the logical opposite of answer choice (D) destroys the conclusion, answer choice (D) states an assumption upon which the conclusion depends.

Does this clear things up? Let me know.

Thanks!

[est15]

Thanks for your explanation. I realized that I wasn't understanding what was being asked for assumption questions so I went back to the Logical Reasoning Bible and re-read that section. I will try answering future assumption questions using what I learned.

[PeterC123]

Hi,

I understood the flaw and prephrased the right answer, however, when I was reviewing I could not get rid of C.

For C, the negated version is "some humans ventured into areas of the forest that were inhabited by chimps", wouldn't this mean that they could have gone in and took the tools from the chimps and started using it? Is it wrong b/c the conclusion never said chimps NEVER used it, just that humans are using it now? I did not view it that way, I thought it was just saying that chimps never used it, it was only used by humans.

Thanks,

[Kristina Moen]

Hi Peter,

We are told that the tools were found in a savanna. While humans lived in the savanna, chimps lived only in the forest. Pay attention to the language here. We are never told that humans live only in the savanna. So when you negate Answer Choice (C) to "Prehistoric humans sometimes ventured into areas of the forest that were inhabited by prehistoric chimpanzees," it does not kill the conclusion. That could be true, and the conclusion could still hold. You are also stretching it a bit by then adding on that the humans then carried the chimp's tools from the forest to the savanna. The test makers were tricky by giving you Answer Choice (A) to plant the idea in your head.

However, if you negate Answer Choice (D) to "The area where the tools were found was a forest at the time the tools were in use," that kills the conclusion. The conclusion that "the tools must have been used by humans rather than by chimpanzees" is based on the assumption that chimps did not live in the area where the tools were found!

Consider this argument: "We found some fossils in Manhattan that look like dinosaur bones. But dinosaurs never lived in bustling cities. So it can't be dinosaur bones!"

[PeterC123]

Ahh ok, so it is never ok to make the leap that I made by saying that humans carried the tools?

Thanks

[Kristina Moen]

Peter,

Since this is an Assumption question, it is something that absolutely unequivocally must be true for the argument to hold. It is difficult for me to give you a definitive answer about "leaps," but when you find yourself saying "Well, but then humans might have taken tools from the chimps and moved them to the savanna, which means that the tools might have belonged to the chimps," when there is no evidence in the stimulus that humans moved tools from place to place, then it might be time to move on to another answer choice (I'd keep it, but move on). That idea was planted by Answer Choice (A). Furthermore, the premise never states that humans lived only in the savanna. So it's not an assumption that they never ventured into other areas.

Answer Choice (D) is absolutely necessary for the argument to hold. The argument is based on the idea that the tools were found in a place where chimps were not.

[JPConstantine]

Hi,

I understand why D is the correct answer. In essence, the question is assuming that the place where the tools have been found has always been a savannah and thus not livable for chimps. But I wanted to know if I am correct on why answer B is not the right answer.

Answer B suggests that "East Africa has been predominately savanna". When I read this I kept it as a contender because it looked as though it was saying that the place where the tools were found had never at one point been a forest. After doing a blind review I honed in on the word predominately and realized that this leaves space for the area where the tools were found to actually be a forest/not savannah. Is that why answer B would be disqualified?

Thanks,

[Luke Haqq]

Hi JPConstantine!

In short, the answer to your question is yes. Given the "predominately" language of this answer choice, it's possible that the place where the tools were found was indeed a forest.