Through the ages, women have suffered greatly because of wars. Consequently, to protect themselves and their offspring, our female ancestors may have evolved survival strategies specific to problems posed by warfare, says Michelle Scalise Sugiyama of the University of Oregon in the US.

Her findings, based on the comprehensive analysis of traditional stories from across the world, are published in Springer's journal Human Nature. The work is of interest because research to date has focused on the problems warfare poses for men, and how these problems shaped human male cognition.

Scalise Sugiyama studied a sample of forager and forager-horticulturalist societies by looking at archaeological and ethnographic research on lethal raiding. This helped her to compile a list of five 'fitness costs' - ways in which warfare impedes women's chances of surviving and reproducing.

These occur when a woman is killed, a woman is captured, her offspring is killed, a mate is killed or captured, or an adult male kinsman is killed or captured.

The study then reviewed traditional stories about lethal raids that had been handed down for generations by word of mouth. Scalise Sugiyama analyzed a cross-cultural sample of war stories from 45 societies and found that the five fitness costs often feature within these story lines.

The war stories included tales from various North American Indian tribes, the Eskimo of the Arctic, Aborigine groups of Australia, the San of Southern Africa and certain South American tribal societies.

Based on the fitness costs documented in these stories, Scalise Sugiyama believes that ancestral women may have developed certain strategies to increase their odds of survival and their ability to manage their reproduction in the face of warfare.

These include manipulating male behavior, determining whether the enemy's intent was to kill or capture them, and using defensive and evasive tactics to sidestep being murdered or to escape captivity.

Assessing the risk of resistance versus compliance also requires having several sets of knowledge. This includes information about an enemy's warfare practices and how they treat their captives.

The so-called Stockholm Syndrome, in which hostages bond with their captors, could have ancestral roots, hypothesizes Scalise Sugiyama. It often occurs under conditions of physical confinement or physical, sexual, and/or emotional abuse, which are characteristic of captivity in ancestral forager and forager-horticulturalist groups.

This response could have developed as a way to help captives identify and ultimately integrate with enemy groups. This then motivates acceptance of the situation and reduces attempts to resist the captor - which may ultimately increase a woman's chances of survival.

"Lethal raiding has recurrently imposed fitness costs on women. Female cognitive design bears reexamination in terms of the motivational and decision-making mechanisms that may have evolved in response to them," says Scalise Sugiyama.

Reference: Scalise Sugiyama, M. (2014). Fitness Costs of Warfare for Women. Human Nature. DOI 10.1007/s12110-014-9216-1