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.
Why are dogs so good at reading our emotions? Horizon meets Betsy, reputedly the world's most intelligent dog, and compares her incredible abilities to those of children. Man's best friend has recently gone one step further - helping us identify genes responsible for causing human diseases.

- The Secret Life of the Dog, BBC Horizon