The oldest debate since humans have been having debates is whether our species is good or evil. This debate has been dominated by philosophers and theologians, and our legal, economic and social policies depend critically on the answer. Now neuroscience has provided new evidence on our human nature. My collaborators and I have done ten years of research in the laboratory and field to establish that oxytocin is the "moral molecule". See how and why I became obsessed with oxytocin in my 2011 talk at TED Global in Edinburgh, Scotland.