"Am I my brother's keeper?" What drives a human being to raise his hand against another, and what holds us back? The story of Cain and Abel, told slowly, and beside it what behavioural science knows about envy, injury and the double nature of the human being. With a surprising ending: the murderer receives protection.

Topics: Genesis 4, envy and comparison, injury as a trigger of violence, in-group and out-group, the Neolithic Revolution, empathy and reconciliation in primates, and the mark of Cain as a mark of protection.

Sources and notes: Genesis 4 (the offerings, the warning "sin crouches at the door, but you can rule over it", the murder, "Am I my brother's keeper?", the mark of Cain), retold freely; short quotations follow the public-domain World English Bible; in the text itself the mark of Cain is explicitly a mark of protection, not a curse. The human being as at once an extraordinarily cooperative and a very violent species; status and injury as strong triggers of violence; in-group and out-group thinking: broad consensus in behavioural science. The Neolithic Revolution (settling down, agriculture, stores, property) roughly 10,000 to 12,000 years ago; earliest traces of organized violence in early settlements (walls, weapons, skeletal injuries). Empathy, fairness, consolation and reconciliation in primates: the work of Frans de Waal. Why one person pulls the brake in the decisive moment and another does not is scientifically not conclusively explained; named as an open question in the episode. Cultural echo: Romulus and Remus (Roman founding legend, public domain), mentioned neutrally as a parallel.

Conceived by a human, narrated with the support of AI. Old stories. New knowledge.