#18 - For several centuries there have been hairless dogs

[lday4]

Can you explain why A is incorrect? I thought the stimulus was saying that the dogs must have been transported from/to Mexico from/to Peru. If you negate A, the author can't draw the conclusion because the dogs could have come from elsewhere.

Thanks!

[Nikki Siclunov]

Hi lday4,

This is a classic causal argument. The author observes that a rare trait (hairlessness) emerged in two separate locations (Mexico and Peru), and explains the effect by suggesting that the dogs must have been transported from one of these regions to the other by boat. This line of reasoning assumes that that there was no other way for the dogs to get from Mexico to Peru (or vice versa): i.e. that there is no alternative cause for the observed effect.

Answer choice (E) fits the bill. Let's try the Assumption Negation Technique: what if, centuries ago, travel between Mexico and Peru would have been easier over land than by boat? If so, then clearly the dogs could have been transported by an overland route. One of the premises clearly states that overland travel was extremely difficult, but that doesn't mean it was impossible. What if travel by boat was even more difficult? The assumption is that it wasn't: that's exactly why answer choice (E) is correct.

Answer choice (A) does not need to be assumed for the conclusion to be logically valid. Even if there were hairless dogs elsewhere in the world, it is still possible that they were first transported from Mexico to Peru (or vice versa) by boat. We don't know whether their emergence followed or preceded the emergence of hairless dogs in Mexico and Peru. Of course, if no hairless dogs ever existed anywhere else, then the causal link suggested in the stimulus would be made stronger. However, answer choice (A) need not be assumed for the conclusion to logically follow.

Hope this makes sense! Let me know.

Thanks,

[lday4]

Gotchya - I think I hit a problem because my first instinct with cause and effect is to weaken/strengthen that's why A was appealing. But I need to remember that because this is an CE assumption question, we assume that there is only one cause for the effect stated. Am I thinking of that correctly?

[Nikki Siclunov]

You nailed it! Good job

[LSAT2018]

Can answer (A) be eliminated because it focuses on the past continuing to the present, that the dogs have never been found anywhere except in the regions of western Mexico and coastal Peru? The stimulus, however, focuses specifically on the period, several centuries ago so it could be the case that the dogs appeared in other countries thereafter.

Ps. is this an example of a False Dichotomy? If so, wouldn't answer (A) be acceptable had it said something like the dogs have never been found anywhere except in the regions of western Mexico and coastal Peru several centuries ago?

[Adam Tyson]

The time period here doesn't matter all that much, because the author isn't claiming that hairless dogs can never emerge on two separate occasions, but only that is unlikely that they would do so. If hairless dogs also emerged in, say, New Zealand several centuries ago, his argument would be mostly unaffected, because it could still be unlikely for them to have emerged separately in Mexico and Peru.

I suppose one could call this a False Dilemma, because the author leaves out other possibilities, such as traders going overland despite the difficulty, or large birds carrying the dogs over the mountains, or the dogs swimming from one place to the other, etc., but your proposed change to answer A would still not make it a good answer because it doesn't address those alternate possibilities. When an author is guilty of a False Dilemma, his assumption is that there were no other possibilities for the observed phenomenon, and dogs appearing elsewhere centuries ago doesn't do anything to address how they got from Mexico to Peru or vice versa. We'd need more. For example:

"Hairless dogs were not transported to both Mexico and Peru centuries ago by overland travel from Nicaragua."

or

"Several centuries ago the overland routes between Mexico and Peru were not substantially easier to traverse than they are now."

We can probably come up with more assumptions for this one, but the mere absence of hairless dogs elsewhere is not a required assumption of the argument, since "unlikely" isn't "impossible" or "never."

[Agent00729]

Hi lday4,

This is a classic causal argument. The author observes that a rare trait (hairlessness) emerged in two separate locations (Mexico and Peru), and explains the effect by suggesting that the dogs must have been transported from one of these regions to the other by boat. This line of reasoning assumes that that there was no other way for the dogs to get from Mexico to Peru (or vice versa): i.e. that there is no alternative cause for the observed effect.

Answer choice (E) fits the bill. Let's try the Assumption Negation Technique: what if, centuries ago, travel between Mexico and Peru would have been easier over land than by boat? If so, then clearly the dogs could have been transported by an overland route. One of the premises clearly states that overland travel was extremely difficult, but that doesn't mean it was impossible. What if travel by boat was even more difficult? The assumption is that it wasn't: that's exactly why answer choice (E) is correct.

Answer choice (A) does not need to be assumed for the conclusion to be logically valid. Even if there were hairless dogs elsewhere in the world, it is still possible that they were first transported from Mexico to Peru (or vice versa) by boat. We don't know whether their emergence followed or preceded the emergence of hairless dogs in Mexico and Peru. Of course, if no hairless dogs ever existed anywhere else, then the causal link suggested in the stimulus would be made stronger. However, answer choice (A) need not be assumed for the conclusion to logically follow.

Hope this makes sense! Let me know.

Thanks,

Couldn't similar be said about E, that even if travel wasn't easier between Mexico and Peru by boat than overland, the dog could've come from some third place? So the assumption isn't needed?

[Jeremy Press]

Hi Agent00729,

Not based on the premises the author has used to reach the conclusion. That's an important gloss to remember on Assumption questions: what is truly necessary for this set of premises to support this conclusion? If answer choice E were not true, then there's no logical link between the reason the author has given ("overland travel between them [was] extremely difficult centuries ago") and the conclusion the author has reached (boats must have been used). So the author really is assuming what answer choice E states.

I hope this helps!

[Relaxo]

Hello!

Negating (E) I get:

Centuries ago, it was harder to travel by boat between western Mexico and coastal Peru than to travel by an overland route.

'harder' doesn't mean that necessarily, none went overland, but likely, most people went by boat. Claim in the question stem is that '... the dogs MUST have been transported from one of these regions to others'

Now, I see that no other answer choice comes close to being as adequate as (E), and even though (E) is not perfect, I still choose it?

[Adam Tyson]

Answer E actually IS perfect when you look at the full context of the relationship between the premises and the conclusion, Relaxo. Remember, the only reason the author is insisting that they MUST have been transported by boat was because overland travel was extremely difficult at the time. If it was just as hard or harder to go by boat, then the difficulty of overland travel would not be evidence in favor of a boat trip! The argument - not just the conclusion, but the whole argument, which is the relationship between the evidence and the conclusion - requires the assumption that travel by boat was easier, because otherwise the evidence carries no weight and provides no support for the conclusion.