Murder was a calculated family affair among Iceland’s early Viking settlers. And the bigger the family, the more bloodthirsty.
Data from three family histories spanning six generations support the idea that disparities in family size have long influenced who killed whom in small-scale societies. These epic written stories, or sagas, record everything from births and marriages to deals and feuds.
Iceland’s Viking killers had on average of nearly three times as many biological relatives and in-laws as their victims did, says a team led by evolutionary psychologist Robin Dunbar of the University of Oxford.