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. Rutherford explores how many of the things once considered to be exclusively human are not: we are not the only species that communicates, makes tools, utilises fire or has sex for reasons other than to make new versions of ourselves. Evolution has, however, allowed us to develop our culture to a level of complexity that outstrips any other observed in nature. Rutherford presents Inside Science on BBC Radio 4. His previous books are Creation and A Brief History of Everyone Who Ever Lived.