Ancient texts warn of love turning into hatred, as seen in stories like Cain and Abel or "Et tu, Brute?" This talk explores the neurobiology of hatred based on the biology of love: the oxytocin system, attachment networks, and biobehavioral synchrony, which mature through mother-infant bonding and later support group solidarity and out-group hostility. Using this model, we developed Tools of Dialogue© for Israeli and Palestinian youth. After 8 sessions, participants showed reduced hostility, increased empathy, hormonal changes (lower cortisol, higher oxytocin), and lasting attitudes of compromise. Seven years later, these changes supported their peacebuilding efforts, showing how social synchrony can transform hatred into reciprocity and cooperation. Recorded on 02/14/2025. (#40386)