Self sacrifice and kin psychology in war: threats to family predict decisions to volunteer for a women's paramilitary organization

The conditions that propel humans to make sacrifices for groups of unrelated, and often unknown, individuals has received considerable attention across scientific disciplines. Evolutionary explanations for this type of sacrifice have focused on how men form strategic coalitions organized around kin networks and reciprocity when faced with out-group threats. Few studies, however, have analyzed how wome n respond to external threats. Using data from one of the largest female paramilitary organizations in history we show that women who have more brothers, women whose husbands serve in the military and women without children are more likely to volunteer. These results provide qualified support for the hypothesis that women are more likely to sacrifice for their country when members of their family are at risk. Overall, our analysis suggests that self-sacrifice and intense bonding with an imagined community of unknown individuals, such as the nation state, may arise out of a suite of psychological adaptations designed to facilitate cooperation among kin (i.e. kin psychology). These results can be interpreted within the framework of kin selection showing how individuals come to view unrelated group members as family. They may also shed light on various theories of group alignment, such as ‘identity fusion’ – whereby individuals align their personal identity and interests with those of the group – and on our understanding of evolutionary adaptations that cause women to direct altruism toward in-groups.

Kin selection | kin psychology | identity fusion | self sacrifice | out-group threat | risk tolerance|

Read the accepted manuscript here

 

Other News

Simon's latest work on the demography of grandmothers is now out in PLoS ONE. 

We were delighted to host Professors Martin Daly and Gretchen Perry for a day of excellent talks, with a particular focus on grandmothering and alloparental behaviour.

Robert Lynch is at the Human Behavior and Evolution Society (HBES) conference 2018 in Amsterdam

The manuscript "The transition to modernity and chronic disease: mismatch and natural selection" by Stephen Corbett, Alexandre Courtiol, Virpi Lummaa, Jacob Moorad and Stephen Stea

Two papers out now from Simon's PhD project!

1) Changes in the Length of Grandparenthood in Finland 1790-1959, published in the Finnish Yearbook of Population Reasarch. In this paper, the team investigated how the shared time between grandparents and grandchildren changed across the demographic transition and with industrialisation. This shared time was low and stable before these major events, and began to increase rapidly after they began.

2) Limited support for the X-linked grandmother hypothesis in pre-industrial Finland, published in Biology Letters. Here, we tested whether slight differences in relatedness via the X-chromosome might lead to differences the survival of male and female grandchildren with maternal or paternal grandmothers. Though two of three predictions were supported, we concluded that the X-linked grandmother hypothesis cannot account for lineage differences by itself. 

Our latest paper shows that early-life environment is associated with sex differences in adult mortality and expected lifespan. Out now in Ecology Letters:
http://doi.wiley.com/10.1111/ele.12888

Figure 3a+b, from Griffin et al. 2017

Our review of the contribution of human studies to evolutionary biology is out now in Proceedings of the Royal Society B:
http://rspb.royalsocietypublishing.org/content/284/1866/20171164

Virpi was given the inaugural Phoenix Award from the Turku Finnish University Society on Friday in recognition of and encouragement for her consistently creative and internationally high-quality re

We had the pleasure of hosting Silke van Daalen from the University of Amsterdam for three weeks this September. Silke is a PhD student working with Hal Caswell on identifying individual stochasticity in life-history traits of long-lived populations with a mathematical modelling approach, and came to learn about our dataset and how she might be able to use it in her work. We wish her the best of luck with the rest of her PhD studies, and hope to see her again soon!

Another year, another project meeting! This time we stayed on the beautiful island of Seili, again with the lovely people from the Myanmar Timber Elephant Project, for a few days of talks, drinks, and sauna. Needless to say, there is plenty of interesting and exciting work underway - keep your eyes peeled for the results, coming soon (hopefully) to peer-reviewed journals near you!