“A neuron didn’t know whether it fired in response to a scent or a symphony. Brain cells weren’t intelligent; only brains were. And brain cells weren’t even the lower limit. The origins of thought were buried so deep they predated multicellular life itself: neurotransmitters in choanoflagellates, potassium ion gates in Monosiga. I am a colony of microbes talking to itself, Brüks reflected.”