My ds seems to know all kinds of things I didn't tell him... I honestly don't know where he gets most it... could be just living in NYC, information overload capital of the world. For example when someone recently got on the subway, ranting about "what really happened on 9/11," and distributing a graphic flier, I instinctively tried to shield him... but he matter-of-factly told me he knew all about the planes flying into the buildings, and he really wanted to know if I thought it was a conspiracy, too.
On the subject of the food chain... when we were debating vegetarianism at our dinner table last year, my son said: "It's just nature. Cows eat grass. We eat them."
This became his teenage stepbrother's facebook motto: "Cows: they eat grass, we eat them."
