There's a textbook version of evolution that goes something like this: random changes to an individual's DNA are inherited by its offspring. The worst changes are weeded out by natural selection, and the process goes on. Unless you're an octopus or a squid. New research suggests that cephalopods do something different. They change their RNA. A lot. And that may help explain why they, alone amongst all invertebrates, are so intelligent. To understand the difference, imagine your DNA, or genome,