Overview
- The Science paper, published Thursday, draws on 30 years of observation at Ngogo in Uganda and a decade of GPS tracking to map social ties and movements.
- Ngogo’s ~200 chimpanzees began to polarize in 2015 and, by 2018, had split into western and central groups with separate ranges.
- From 2018 to 2024, researchers recorded at least seven adult male deaths and 17 infant deaths from coordinated raids by the western subgroup, and they report the violence has continued.
- All observed raids were launched by the smaller western group, which the authors say points to strong cohesion and long-term bonds outweighing a numbers advantage.
- The authors argue ruptured relationships can drive collective violence without human-like cultural markers, while outside experts caution against equating these killings with human war and note that permanent chimpanzee fissions appear only about once every 500 years.