In the German hamlet of Herxheim, archaeologists excavating a 7000-year-old mass grave of up to 1000 Stone Age people have concluded that the site was not a Neolithic graveyard, as previously assumed, but a killing field where hundreds of men, women and children met a grisly fate. Scholars now believe that Stone Age Europe was much more violent than previously thought, and some scientists believe the bodies in Herxheim were murdered, cooked and cannibalised in sacrificial rites that drew participants from hundreds of miles away. It's a possibility that calls into question much of what we thought we knew about civilisation, and forces us to face the fact that cannibalism and human sacrifice may be undeniable parts of our human history. This programme follows the investigations.