Vanilla bean != Vanillin, since the smell of natural vanilla bean has a many more components to it other than Vanillin which lend it that characteristic odor (sweet, animalic, slightly woody and herbaceous).
Vanillin by itself is of course a principle component. However, coumarin and vanillin don't smell too similar. Coumarin has more of a herbaceous, 'hay' smell, quite different from vanillin itself.
I know it’s a rhetorical question—but I’m sure that someone discovered animal glues because they were cooking, left the animal products to cook in water, and then let it dry out.
You cook it because it’s supposed to be food, but sometimes you’re left with this thick, sticky substance. Voilà, glue.
Vanillin by itself is of course a principle component. However, coumarin and vanillin don't smell too similar. Coumarin has more of a herbaceous, 'hay' smell, quite different from vanillin itself.