200,000 years ago we took our first steps on the African savanna.   Today there are 7 billion of us living across planet Earth.

How did our ancestors beat the odds and spread from continent to continent?  What was the secret to their success?

This is a global detective story, featuring new fossil finds and the latest genetic research.  It's a story that revolves around a shocking revelation.  In prehistoric times, we met and mated with other types of human - like Neanderthals, Denisovans, and Homo erectus. This mixing of genes helped us survive - and ultimately thrive.

Scientists are beginning to realise that ours is not a pedigree species, but a patchwork.  We are all hybrids.