Male bowerbirds construct elaborately decorated nests, or bowers. Basi

A certain surfing GMAT tutor couldn't resist googling bowerbirds, and he discovered that male bowerbirds really do construct incredibly elaborate nests. Why? Just to impress the lady bowerbirds, apparently.

But as you already know, it's a terrible idea to let any of that outside information enter your mind at all. So back to the fun stuff: let's start by identifying the conclusion of the researchers, which is that "the bowerbirds' building styles are a culturally acquired, rather than a genetically transmitted, trait." In other words, those researchers conclude that bowerbirds are not born with those building styles. Instead, the birds must learn those building styles.

Now let's think about the structure of the researchers' argument. How do they arrive at that conclusion?

• We know that male bowerbirds build elaborately decorated nests, which are called bowers.
• "Different local populations of bowerbirds of the same species build bowers that exhibit different building and decorative styles." - So the building/decorative styles vary among local groups of these birds.
• Based on this variation, researchers conclude that the building styles must be a learned ("culturally acquired") trait. After all, if the building styles were genetically transmitted, why wouldn't the different local groups all have similar building/decorative styles?

Now we need to find an answer choice that most strengthens the researchers' conclusion, so use process of elimination:


Notice that this choice only describes ONE local population (the one that has been studied most extensively). Within that group, there are more common characteristics than there are differences among bower-building styles. Those similar characteristics could have been culturally acquired within the group OR genetically transmitted. We can't tell either way, so choice (A) doesn't strengthen the conclusion. Eliminate this one.


Young males have NO bower-building skills and must spend years watching their elders before becoming accomplished (highly skilled). This suggests that the young males must LEARN how to build bowers from their elders. If the skills were genetic transmitted, then the males would probably not need to watch and learn from their elders. Choice (B) suggests that the bowerbirds' building styles are culturally acquired (learned), which supports the conclusion. Hang on to this one.


Pay close attention to the details here. Choice (C) compares one species of bowerbird to most other species of bowerbirds. The passage, on the other hand, is concerned with "different local populations of bowerbirds of the same species." Thus, choice (C) has no bearing on the evidence in the passage or the conclusion. Eliminate (C).


We already know that different local populations of bowerbirds of the same species build bowers that exhibit different building and decorative styles. Now we also know that those local populations probably don't have much contact with one another. This suggests that the groups probably don't learn much from one another (little "cultural acquisition" between groups). If the groups had LOTS of contact, that might weaken the conclusion--e.g. if the building styles are culturally acquired and the groups are in constant contact, then why would they have different styles?

But choice (D) doesn't help us to understand the observed DIFFERENCES. Are those differences cultural acquired or is there some other explanation (i.e. a genetic explanation)? This information does not help support (or weaken) the conclusion and should be eliminated.


Choice (E) does support the idea that learned (i.e. culturally acquired) traits DO exist among some songbirds. But are bowerbirds songbirds? Even if they are, are they one of the songbirds whose song dialects are learned rather than genetically transmitted?

Choice (E) certainly doesn't hurt the conclusion. The conclusion is still possible given this new information, but, unlike choice (B), the new information does not do much to strengthen the given argument.

Choice (B) is the best choice.