Logical Reasoning

PT148 · S4 · Q22 Scientists once believed

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Scientists once believed that the oversized head, long hind legs, and tiny forelimbs that characterized Tyrannosaurus rex developed in order to accommodate the great size and weight of this prehistoric predator.

Conclusion

This belief must be abandoned (the T-Rex's big head, long legs, and tiny hands did not develop in order to deal with T-Rex's big size and weight).

Evidence

We found a skeleton of an earlier dinosaur that had the T-rex features but not the T-rex's big size and weight.

Evaluate

This is a confusing argument to even understand at first. It's related to the logic of evolution. Scientists believed that the T-rex combo (big head, big legs, tiny hands) was an adaptation T-rex had to balance out its huge size and weight.

However, if an earlier dinosaur (i.e. earlier on the evolutionary tree) had the T-rex combo but not the huge size and weight, then it suggests that the T-rex combo of features evolved as some other adaptation.

This plays off the evolutionary common sense that you probably wouldn't see two very similar sets of physical features that were the result of very different needs. If we know that gills are an adaptation to breathing underwater, and then we find gills on a prehistoric creature, we probably wouldn't put much credence into the idea that .

If we're going to weaken this argument, we need to defend the idea that the T-rex combo of features WAS an adaptation to its big size and weight.

So the onus is on us to explain away what's going on with this skeleton that seems to have the T-rex features, even though it didn't need an adaptation for big size and weight.

Goal

Look for an answer that can "make an excuse" for this skeleton that looks like a counterexample, so that we can protect the original notion that T-rex's big head / big legs / small hands was an adaptation to balance out its big size and weight.

22.

The answer to which one of the following questions would most help in evaluating the argument?

Was the ratio of the
No Impact
It seems like we already know that the ratio wasn't the same, since we know this skeleton dinosaur had the big T-Rex head but was 1/100 the weight (so probably had a smaller body). Even if we didn't already know that the ratio wasn't the same, saying that the ratio "wasn't the same" isn't a great objection. On Necessary Assumption, the concept of "same" is almost always wrong. When you negate it, you get "different", which is too unspecific to have clear impact. If you replace the word "same" with "identical", it's easier to hear how unimportant this distinction is. Does the ratio need to be identical in order for this skeleton to qualify as noteworthy counterevidence? Doesn't seem like identical is necessary. If it were 98% the same, we'd still be intrigued by how to explain this skeleton.
23% picked this
Correct
At what stage in its
Why this is right
If we're unsure about the potential usefulness of this question, consider extreme answers: what if it died late in life, as a geriatric dinosaur? What if it died very early in life, as a dino-toddler? That second one would actually be a way to "make an excuse" for this skeleton. If we found the skeleton of a baby T-Rex, it would have the characteristic T-Rex features but be 1/100 the weight. This is one of the weirdest correct answers ever. It lives in infamy as the "baby T-rex" question. One annoying aspect of this problem is that this skeleton is identified in the paragraph as an "earlier" dinosaur, which seems to mean that this skeleton predates when T-Rex was known to exist. So this isn't really a baby T-rex, but whatever this earlier species is, it looks like a possible precursor to T-rex. The important point remains the same: the T-Rex features might still have been an adaptation to big size and weight. The fact that this skeleton was 1/100 the weight could be because it was still a tiny, growing child version of the species.
Skill tested: Evaluate · how this choice captures the argument's function is the move to repeat next time.
52% picked this
Was T rex the largest
Too Strong: largest / heaviest
Does it matter whether T-rex is the #1 heaviest / largest vs. the #2 heaviest / largest? No, that distinction would have no impact on the argument.
2% picked this
Was the species to which
Weak Impact
If we say that the species was related to T-Rex, it still serves as a potential counterexample -- given that this skeleton had the T-rex "family" features but didn't have massive size or weight, it would imply that these features aren't an adaptation to size and weight. If we say that the species was not related to T-Rex, we have something more like an objection. "That skeleton doesn't disprove what we said about T-Rex's features being an adaptation to size/weight ... it's just a skeleton from an unrelated species!" LSAC must consider that objection to be weaker than the one we get from saying the skeleton was just a baby. It kind of goes back to the evolutionary common sense we talked about in the analysis: if gills are used by some species for breathing underwater, we still doubt that another species developed the same adaptation for a completely different reason. There are a lot of unrelated species, for example, that have spikes or armor on their backs, as an adaptation to make it harder for predators to eat them. There are tons of unrelated species that all have similar looking eyes, that are all adaptations for the sake of vision.
20% picked this
Did the recently discovered dinosaur
Out of Scope: size of prey
The size of this mystery animal's prey is too remote from what we're analyzing. Can we weaken the argument by saying that this mystery animal preyed on animals just as big as T-rex's prey? Can we weaken by saying that it ate smaller animals? I'm not seeing how that would explain away the fact that it has T-rex's features but not T-rex's size.
4% picked this

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