Humans, being conditioned to blink their eyes, and marine sea slugs, conditioned to withdraw their gills, haven’t shared a common ancestor for more than half a billion years. And here we are, with their neurons and ours using the same intracellular machinery for changing in response to experience. You and an Aplysia could trade your cAMPs, PKAs, MAPKs, and so on, and things would work just fine in both of you.[*6]
