From the latest fossil evidence, to the sequencing of the canine genome, to cognitive experiments, dogs are fast turning into a window into understanding ourselves. We have an extraordinary relationship with dogs closer than with any other animal on the planet. But what makes the bond between us so special? Where does this relationship come from? In Siberia, a unique breeding experiment reveals the astonishing secret of how dogs evolved from wolves. Swedish scientists demonstrate how the human/dog bond is controlled by a powerful hormone also responsible for bonding mothers to their babies.