That is not the set up to a joke. A few weeks ago, researchers finally answered a question that has stumped everyone from Aristotle to Sigmund Freud (yep, before he got into psychoanalysis, he was cutting up eels, fruitlessly looking for their sex organs – figures): where do eels come from?
> "the present distance back to the breeding grounds is an accident of geography."
That wouldn't explain Pacific eels though, would it?