Of all life on Earth, how come we're the only ones with the smarts to leave our planet? For three billion years, nothing had a brain. Even today, over 90 percent of life doesn't need a brain to survive. So, what happened? How did our planet set in motion the chain of nearly impossible events that gave us our unique intelligence? The greatest mystery of all may be right between your ears. Astronaut host – Leland Melvin.