“She tells me about ancient lines drawn in red ochre on the ceiling of a Spanish cave. Apparently, at first, the lines seem random and abstract—arbitrary markings, simple shapes—but if looked at in a certain way they begin to shift and coalesce, cohering into a single figure: a babirusa, or deer-pig. Just think, she says. This could be a record of the moment our species first woke up to its own cognition. The modern mind switched on like a light.”