Levin doesn’t believe this should be incendiary in any way. “If you think brains and neurons are special, you have to ask yourself: ‘How did they get here?’” he said. In the yawning span of time before evolution produced the first neuron, cells found other ways to navigate their environment, “doing pretty much the same thing that neurons do, just at slower speeds”. There’s no reason to think that, upon the arrival of the first synapse, evolution – a notorious hoarder – would merely have wiped away the older mechanisms that had existed for billions of years.
Which isn’t to say that humans are indistinguishable from single cells, Levin pointed out. “The way I explain the continuum is with the word ‘adult’.” The word’s function is to smooth the business of everyday life: voting, driving, drinking, buying fireworks, joining the army. “But we all know that no great shift happens on your 18th birthday, right?” Levin said. “The word ‘adult’ sweeps under the rug all the deep questions about personal responsibility, and when we acquire it, and how we acquire it.”
Many of these terms such as “cognition” and “memory” are just like that, Levin said. “They’re not sharp scientific categories.” He considers putting quotes around words a weaselly move. “Sometimes the slime mould knows, not ‘knows’, and there’s nothing scientific added by using the quotes,” he said. “Of course, that’s not the same thing as saying it knows that it knows. So we just need to have the right words and use them carefully, and not invent new ones because we want to be special.”
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