Memes are to culture what genes are to biology: the base unit of evolution. The term was originally coined by the evolutionary biologist Richard Dawkins in his 1976 book, The Selfish Gene. Dawkins writes, "I think that a new kind of replicator has recently emerged . . . It is still drifting clumsily about in its primeval soup, but already it is achieving evolutionary change at a rate which leaves the old gene panting far behind." He goes on, "Examples of memes are tunes, ideas, catch-phrases, clothes fashions, ways of making pots or of building arches. Just as genes propagate themselves in the gene pool by leaping from body to body via sperms or eggs, so memes propagate themselves in the meme pool by leaping from brain to brain, via a process which, in the broad sense, can be called imitation."3
This is our topic for today: the way things move and spread, somewhat chaotically, across a network. Some examples to whet the appetite:
Infectious diseases jumping from host to host within a population
Memes spreading across a follower graph on social media
A wildfire breaking out across a landscape
Ideas and practices diffusing through a culture
Neutrons cascading through a hunk of enriched uranium