The World Without Us
Last week's question: How are the arches at Arches formed?
You can tell I'm running out of ideas when the questions are so straight forward. The arches are actually formed the same way as any other rock formation - through wind and water erosion. It's just that the rocks on top have the correct hardness and weight to withstand the erosion while the center crumbles away.
This week's question is more interested. Literature has featured anthropomorphic animals for a long time. What spieces, and at what point of anthropomorphing, can animals take over (ie. extinguish, possibly drive to extinction) the human race?
But it's really the title text I like: "When I say we should do something sometime, I'm secretly hoping you'll say 'Why not now?'"