My favorite example of a crucial meme would be "fire" or more importantly, "how to make a fire." This is a behavioral meme, mind you, one which didn't necessarily need a word attached to it to spring up and spread, merely a demonstration for another to follow. Once the meme was out there, it would have spread like wildfire, for obvious reasons...

But when you start to think of memes like that -- behavioral memes -- then you can begin to see how language itself, the idea of language, was a meme. Writing was a meme. And within those areas, more specific memes emerged.