An adult skull from the Charterhouse Warren mass grave in the UK, featuring cut marks and a blunt force fractureIan R. Carwright/Institute of Archaeology Oxford UniversityAround 4000 years ago, at least 37 men, woman and children were brutally butchered, dismembered and possibly eaten by their enemies before their remains were tossed into a 15-metre-deep cave shaft with cattle bones.It is the largest and most extreme episode of mass violence known from prehistoric Britain. The archaeologists behind the discovery think the perpetrators did it to dehumanise, or other, the victims, possibly as revenge to send a political message.