You think you're human. But what does that mean? How can humanity be defined? Felipe Fernandez-Armesto takes us on an enlightening journey through the history of humankind to reveal the challenges to our most fundamental belief - that we are, and have always been, human. Chimps and humans are objectively so alike that an anthropologist from Mars might classify them together; advances in artificial intelligence mean that humans no longer have exclusive access to reason, consciousness and imagination; developments in genetics threaten humanity with an uncertain future. The harder we cling to the concept of humanity, the more slippery it becomes. But if it breaks down altogether, what will this mean for human values, human rights, and the defence of human dignity? So You Think You're Human? confronts these problems from a historical perspective, showing how our current understanding of what it means to be human has been shaken by new challenges from science and philosophy. Fernandez-Armesto shows how our concept of humankind has changed over time, tracing its faltering expansion to its present limits and arguing that these limits are neither fixed or scientifically verifiable. Controversially, he proposes that we have further to go in developing our concept of humankind and that we need to rethink it as a matter of urgency.