The common ancestors of Australian

Answer choices

1. A

   Opposite: exacerbates paradox12% picked this

   Modern tree-dwelling kangaroos must back down tree trunks slowly and carefully, but the common ancestors of modern tree-and land-dwelling kangaroos used their opposable

   This answer just underscores how USEFUL it would have been to the modern tree-kangaroo to keep those traits that the ancient kangaroos had. So we're even more confused why evolution edited out those traits.

   12%
2. B

   Irrelevant Comparison1% picked this

   Modern tree-dwelling kangaroos are smaller than most modern land-dwelling kangaroos but larger than

   This gives us a size gradient for the three styles: Ancient K's < Modern Tree K's < Modern Land K's But that gradient doesn't give us any causal explanation for how the ancient K's lost the tree-friendly traits. There's no common sense link from, "modern tree K's are somewhat bigger" to "that's why they no longer have these tree-friendly traits".

   1%
3. C

   Cheats Paradox, if anything4% picked this

   Modern tree-dwelling kangaroos’ tails cannot grasp branches, but they are somewhat longer and more flexible than those

   This doesn't explain how the ancient K's lost their tree-friendly traits en route to evolving into the modern tree K's. If anything, it tries to make it seem like modern tree K's do still have tree-friendly adaptations.

   4%
4. D

   Correct81% picked this

   Modern tree-dwelling kangaroos are descended from species of land-dwelling kangaroos that had been land-dwellers for many generations before modern

   Why this is right

   This shows that the modern Land and Tree kangaroos didn't both evolve from the ancient ones. Rather, ancient K's evolved into Land K's, and then Land K's evolved into Tree K's. Since there was a long stage in between (for many generations), there was time for Land Kangaroos to lose those tree-friendly traits that the ancient kangaroos had. After all, those traits wouldn't have been particularly useful to land kangaroos, and so it's perfectly plausible that those traits would be edited out by natural selection (useful traits persist .. harmful or useless traits tend to disappear).

   Skill tested: Paradox · how this choice captures the argument's function is the move to repeat next time.

   81%
5. E

   Irrelevant Comparison / Unrelated to Goal2% picked this

   Modern tree-dwelling kangaroos have smaller and weaker hind legs than modern land-dwelling kangaroos, and they move more slowly on land

   This doesn't seem related to our goal of explaining how ancient kangaroos lost their tree-friendly traits along the evolutionary path to modern tree kangaroos. This just compares modern land K's to modern tree K's, but the distinction doesn't tell us anything about how modern tree K's "lost" the tree-friendly traits that the ancient K's had.

   2%