As air-breathing mammals, whales must once have lived on land

Question

As air-breathing mammals, whales must once have lived on land and needed hind limbs capable of supporting the mammals' weight. Whales have the bare remnants of a pelvis. If animals have a pelvis, we expect them to have hind limbs. A newly discovered fossilized whale skeleton has very fragile hind limbs that could not have supported the animal's weight on land. This skeleton had a partial pelvis.

If the statements above are true, which one of the following, if also true, would most strongly support the conclusion that the fragile hind limbs are remnants of limbs that land-dwelling whales once had?

(A) Whale bones older than the fossilized hind limbs confirm that ancient whales had full pelvises.

(B) No skeletons of ancient whales with intact hind limbs capable of supporting the mammals' weight have ever been found.

(C) Scientists are uncertain whether the apparently non-functioning limbs of other early mammals derived from once-functioning limbs of their ancestors.

(D) Other large-bodied mammals like seals and sea lions manoeuvre on beaches and rocky coasts without fully functioning hind limbs.

(E) Some smaller sea-dwelling mammals, such as modern dolphins, have no visible indications of hind limbs.

sobby · Answer

Two point to notice in the argument:

1. If animals have a pelvis, we expect them to have hind limbs
2. This skeleton had a partial pelvis.

A supports the concept ......

chesstitans · Answer

yup, if ones follow the flow of the argument, then A strengthens the conclusion. Nevertheless, in some situations, the argument can be strengthened if we rule out all other possibilities. Under such scenarios, it is hard to interpret completely all of options.

For example, D or E can causes much trouble if either of the option is changed into a sentence that contains a contradictory possibility with A. Then, it probably takes much more time to find the correct answer.

Skywalker18 · Answer

there really isn't a core to this argument yet we can still analyze it just the same. It is a strengthen question.

Facts: 
(1) Land-dwelling mammals needed hind limbs
(2) If animals had a pelvis, they had hind limbs
(3) Fossilized whale had fragile hind limbs and a partial pelvis
Conclusion: Fragile hind limbs are remnants of limbs that land-dwelling whales once had

So from what is given above, we need to support the conclusion. This a problem primarily about "evolutionary leftovers." We know that these whales had very fragile limbs and a partial pelvis - how can we conclude that this is all pointing to them having limbs sufficient to be land-dwelling? What I was initially thinking was that I would get something about evolution. Perhaps an answer choice would say something like, "There is evidence from fossils that date before the newly discovered fossil that whales had a stronger pelvis" - something like that. Perhaps it would give me an example of how whales have evolved in other aspects. Either way, without having a core it is really hard to pre-phrase the right answer.

(A) Well if they had full pelvises then, according to the stimulus, "we expect them to have hind limbs." This seems like a really good answer choice so I'll skip it and move on.

(B) This actually is the opposite of what I was initially looking for. I was looking for something saying that fossils have been found that gives some evolutionary evidence that there was some hind limbs.

(C) This is definitely wrong because, like (B), this makes us uncertain if we can really conclude a connection between the remnants of a limb and actually having a limb. This is saying that even scientists are uncertain as to if nonfunctioning limbs, i.e. the limbs shown in this fossilized whale, "derived from once-functioning limbs," aka the land-dwelling limbs that we are trying to assert that whales use to have. Now I will say that this answer choice is still about "other" mammals. So it could also be treated as a bit out of scope too.

(D) This is about the ability to land-dwell. Yet this isn't what we are concerned about! We are concerned about having the limbs necessary for land dwelling. We don't care if they actually land-dwelled or not - that is just a secondary tidbit of information.

(E) This is just out of scope, perhaps even weakening. It seems that we are talking about sea-mammals (dolphins) now when we are really concerned about sea-mammals then. However, it may also weaken because this continues to destabilize the link between used to having functioning limbs and not having functioning limbs. We want to link up those two things as much as possible - aka that not having limbs now still doesn't necessarily mean they didn't have limbs then.

Damion123 · Answer

As air-breathing mammals, whales must once have lived on land and needed hind limbs capable of supporting the mammals' weight. Whales have the bare remnants of a pelvis. If animals have a pelvis, we expect them to have hind limbs. A newly discovered fossilized whale skeleton has very fragile hind limbs that could not have supported the animal's weight on land. This skeleton had a partial pelvis.

If the statements above are true, which one of the following, if also true, would most strongly support the conclusion that the fragile hind limbs are remnants of limbs that land-dwelling whales once had?

Given:

1)Whales must have lived on Land and needed hind limbs capable of supporting the mammals' weight
2) Whales have the bare remnants of a pelvis and if pelvis --> have hind limbs
3) A newly discovered fossilized whale skeleton has very fragile hind limbs that could not have supported the animal's weight on land. This skeleton had a partial pelvis.

Conclusion:

very fragile hind limbs are remnants of limbs that land-dwelling whales once had

(A) Whale bones older than the fossilized hind limbs confirm that ancient whales had full pelvises.  Option Says Whale bones older than the fossilized hind limbs --> ancient whales had full pelvises and from Premises we can infer that Whales have the bare remnants of a pelvis and if pelvis --> have hind limbs
 
(B) No skeletons of ancient whales with intact hind limbs capable of supporting the mammals' weight have ever been found.  Opposite of what is given in premises .

(C) Scientists are uncertain whether the apparently non-functioning limbs of other early mammals derived from once-functioning limbs of their ancestors.  OFS

(D) Other large-bodied mammals like seals and sea lions manoeuvre on beaches and rocky coasts without fully functioning hind limbs.  OFS

(E) Some smaller sea-dwelling mammals, such as modern dolphins, have no visible indications of hind limbs.  OFS

MBAToronto2024 · Answer

KarishmaB 
So answer D almost connects all dots: Pelvis -> Limbs -> Walking on the earth. If the answer connects the dots, then it's usually the correct one. But it does no answer the question. 
A - on the other hand, it sounded too simple. What would you recommend in such cases?

KarishmaB · Answer

As air-breathing mammals, whales must once have lived on land and needed hind limbs capable of supporting the mammals' weight. Whales have the bare remnants of a pelvis. If animals have a pelvis, we expect them to have hind limbs. A newly discovered fossilized whale skeleton has very fragile hind limbs that could not have supported the animal's weight on land. This skeleton had a partial pelvis. Conclusion to be supported: The fragile hind limbs are remnants of limbs that land-dwelling whales once had We want to support that fragile hind limbs are a remnant of proper hind limbs that they had in the past. (A) Whale bones older than the fossilized hind limbs confirm that ancient whales had full pelvises. We are given that if animals have a pelvis, we expect them to have hind limbs (premise). We want to support that whales had proper hind limbs in the past. The fossil shows partial pelvis. If we find older fossils that had full pelvises, it increases the probability that the whales had hind limbs. Hence it supports the conclusion that the partial hind limbs are remnants of proper hind limbs that whales had in the past. MBAToronto2024 - We cannot eliminate an option because it looks so simple and satisfying. We know that in many assumption questions, the simplest option is the answer. If you cannot see a trap in the option, you should consider it seriously. (B) No skeletons of ancient whales with intact hind limbs capable of supporting the mammals' weight have ever been found. This makes it less likely that whales had proper hind limbs. Does not support the conclusion. (C) Scientists are uncertain whether the apparently non-functioning limbs of other early mammals derived from once-functioning limbs of their ancestors. Again, this makes our conclusion less likely. It says that scientists are uncertain whether partial limbs derived from actual limbs. Hence it suggests that scientists don't know whether connect exists between presence of partial limbs and presence of full limbs. (D) Other large-bodied mammals like seals and sea lions manoeuvre on beaches and rocky coasts without fully functioning hind limbs. This is irrelevant because large bodied is not sufficient to say that the requirements of whales and these other mammals are the same. Perhaps whales have much more wight and hence their requirements are different. If this option does have any relevance, it weakens our argument. We are given that whales would have needed hind limbs capable of supporting their weight on land. If there are other large-bodied mammals that make do on land without hind limbs, then it weakens that whales had hind limbs in the past. Perhaps they were able to make do without hind limbs too. (E) Some smaller sea-dwelling mammals, such as modern dolphins, have no visible indications of hind limbs. Small sea swelling animals are irrelevant. Answer (A) Another interesting strengthen question here: https://youtu.be/9o3y4Hz16es

As air-breathing mammals, whales must once have lived on land

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As air-breathing mammals, whales must once have lived on land

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