T-Rex is having an identity crisis. Rocking the world of paleontology is the claim that Rex was not one species, but actually three. It's not the first time that this particular dino has forced us to revise our understanding of the past. The discovery of the first T-Rex fossil in the 19th century taught humanity a scary lesson: species eventually go extinct. If it happened to this seemingly invincible apex predator, it could happen to us too. Hear how the amateur fossil hunter Barnum Browns discovery of T-Rex changed our understanding of ourselves, and the epilogue to the dinosaur era: how our mammalian relatives survived the potential extinction bottleneck of an asteroid impact.