We like to think of ourselves as exceptional beings, but is there really anything special about us that sets us apart from other animals? Humans are the slightest of twigs on a single family tree that encompasses four billion years, a lot of twists and turns, and a billion species. All of those organisms are rooted in a single origin, with a common code that underwrites our existence. This paradox - that our biology is indistinct from all life, yet we consider ourselves to be special - lies at the heart of who we are.