As we stand on the brink of the age of AI where technology might one day outstrip human intelligence, Professor Jim Al-Khalili unravels the mysteries of arguably the most complex object in the cosmos: the human brain. From ancient marine animals to modern humans, Secrets of the Brain investigates the evolution of the brain over hundreds of millions of years.

Our brains contain a remarkable story, forged in a cauldron of planetary catastrophes, epic conflicts, death, sex, kinship, and love. At its core, the series investigates how Earth's physical conditions drove the brain's development. Among many new discoveries, Jim will find out: how vicious prehistoric predators transformed neural circuitry, how warm-bloodedness evolved and shaped the brain’s ability to remember; how when worms huddle together, they use the same chemicals as we do when we fall in love; and how competition, friendship, nurturing, playfulness, song, and laughter helped evolve our brains.

In this BBC Horizon special, join Jim on his neural odyssey as he solves puzzles with chimpanzees, snorkels with sea anemones, undergoes state-of-the-art brain scans, and interviews leading experts—all to tell the story of how the brain evolved, as never before.