Women live longer than men almost anywhere in the world. The question is whether this is due primarily to behavioural differences and social factors, or whether biological factors also play a role. To better understand the female survival advantage, Zarulli et al. (2018) investigated the survival of men and women in seven populations under extreme conditions due to famines, epidemics and slavery. They found that even when mortality was very high, women lived longer on average than men. Most of the female advantage was due to differences among infants with baby girls being able to survive harsh conditions better than baby boys. Behavioural differences are unlikely to play a crucial role at this age and social factors may be neutral or favour male survival. Thus, the results of the biodemographic research of Zarulli et al. add another piece to the puzzle of gender differences in survival by suggesting that although the female survival advantage is influenced by socially and environmentally determined risks, opportunities and resources, it also stems from fundamental biological roots.