Critical Reasoning

Male bowerbirds construct elaborately decorated nests, or bowers. Basing their judgment on the fact that different local populations of bowerbirds of the same species build bowers that exhibit different building and decorative styles, researchers have concluded that the bowerbirds' building styles are a culturally acquired, rather than a genetically transmitted, trait.

Which of the following, if true, would most strengthen the conclusion drawn by the researchers?

A. There are more common characteristics than there are differences among the bowerbuilding styles of the local bowerbird population that has been studied most extensively.

B. Young male bowerbirds are inept at bowerbuilding and apparently spend years watching their elders before becoming accomplished in the local bower style.

C. The bowers of one species of bowerbird lack the towers and ornamentation characteristic of the bowers of most other species of bowerbird.

D. Bowerbirds are found only in New Guinea and Australia, where local populations of the birds apparently seldom have contact with one another.

E. It is well known that the song dialects of some songbirds are learned rather than transmitted genetically.

OA:B

P.S: Although I got this one right, I'd like to know why exactly Option D is wrong ?
@Verbal Experts - could you please share your analysis ?

RBBmba@2014 wrote:Male bowerbirds construct elaborately decorated nests, or bowers. Basing their judgment on the fact that different local populations of bowerbirds of the same species build bowers that exhibit different building and decorative styles, researchers have concluded that the bowerbirds' building styles are a culturally acquired, rather than a genetically transmitted, trait.

Which of the following, if true, would most strengthen the conclusion drawn by the researchers?

A. There are more common characteristics than there are differences among the bowerbuilding styles of the local bowerbird population that has been studied most extensively.

B. Young male bowerbirds are inept at bowerbuilding and apparently spend years watching their elders before becoming accomplished in the local bower style.

C. The bowers of one species of bowerbird lack the towers and ornamentation characteristic of the bowers of most other species of bowerbird.

D. Bowerbirds are found only in New Guinea and Australia, where local populations of the birds apparently seldom have contact with one another.

E. It is well known that the song dialects of some songbirds are learned rather than transmitted genetically.

OA:B

P.S: Although I got this one right, I'd like to know why exactly Option D is wrong ?
@Verbal Experts - could you please share your analysis ?

Imagine that you're observing bowerbirds in New Guinea. You're examining the distinctive style of the nests of Population A and you're trying to settle a nature-nurture debate. Did these birds learn this style from other birds, or are they simply genetically programmed to build this way? If you already know that the nests in Population A are different from the nests in Population B, why would knowing that birds from A and B rarely interact help you settle this debate? If the nests are different, there was never any reason to suspect that the birds from Population A were learning anything from the birds from Population B. So within A , there are still two possibilities. Either some birds in A are learning their nest-making from other birds in A, and the trait is culturally acquired, or the birds in A are somehow genetically distinct from the birds in B, and it's the genes that dictate the style of the nests. D doesn't tell us this.

@Dave - I think, you meant that Population A and Population B are from New Guinea and Australia respectively. Right ?

RBBmba@2014 wrote:@Dave - I think, you meant that Population A and Population B are from New Guinea and Australia respectively. Right ?

That is what I had in mind, but really, the same logic would hold whether we were talking about two distinct populations within New Guinea, or one population in Australia and one population in New Guinea. The fact that two populations, each with its building style, don't interact with each other tells us nothing about whether their respective building styles are dictated by genetics or transmitted via culture.

DavidG@VeritasPrep wrote:

RBBmba@2014 wrote:@Dave - I think, you meant that Population A and Population B are from New Guinea and Australia respectively. Right ?

That is what I had in mind, but really, the same logic would hold whether we were talking about two distinct populations within New Guinea, or one population in Australia and one population in New Guinea. The fact that two populations, each with its building style, don't interact with each other tells us nothing about whether their respective building styles are dictated by genetics or transmitted via culture.

True.
That said, isn't it BIT AWKARD to presume that two distinct populations are in New Guinea itself (or in Australia) ? I mean, is it realistic to presume such ?

ceilidh.erickson wrote:Option D states that local populations seldom have contact with one another. This would imply that they do not share cultural practice (supporting the argument), but it would equally support the contention that these groups might not share all genetically transmitted traits (weakening the argument).

ceilidh - I guess, the supporting/weakening the CONCLUSION conditions need to swapped their places.

do not share cultural practice -- weakening the CONCLUSION PARTIALLY.

might not share all genetically transmitted traits -- supporting the CONCLUSION PARTIALLY.

So, either way option D is out.

Correct me please if wrong!

True.
That said, isn't it BIT AWKARD to presume that two distinct populations are in New Guinea itself (or in Australia) ? I mean, is it realistic to presume such ?

Here's one thing I can confidently say about the GMAT: the test-maker has very little expectation about our knowledge regarding the migratory patterns of birds.

(And for what it's worth, it doesn't necessarily seem unrealistic to me. Within a larger landmass, I see no reason why you couldn't have multiple populations that don't interact. But no question would ask us to assume this one way or the other.)

I thought option A would be most appropriate. It supports the argument that bower building style is culturally influenced.
The other statements are presuming and bringing in additional data that is not discussed in the question.