Child volunteers in a women's paramilitary organization in World War II have accelerated reproductive schedules

Robert Lynch,Simon N Chapman,John Loehr,Virpi Lummaa,Michael Briga

doi:10.1038/s41467-020-15703-0

Robert Lynch, Simon N Chapman + Show 3 more

Open Access

https://doi.org/10.1038/s41467-020-15703-0

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Journal: Nature Communications	Publication Date: May 12, 2020
Citations: 8	License type: open-access

Affiliation: University of Turku, University of Helsinki

Abstract

Understanding how conditions experienced during development affect reproductive timing is of considerable cross-disciplinary interest. Life-history theory predicts that organisms will accelerate reproduction when future survival is unsure. In humans, this can be triggered by early exposure to mortality. Previous studies, however, have been inconclusive due to several confounds that are also likely to affect reproduction. Here we take advantage of a natural experiment in which a population is temporarily divided by war to analyze how exposure to mortality affects reproduction. Using records of Finnish women in World War II, we find that young girls serving in a paramilitary organization wait less time to reproduce, have shorter inter-birth intervals, and have more children than their non-serving peers or sisters. These results support the hypothesis that exposure to elevated mortality rates during development can result in accelerated reproductive schedules and adds to our understanding of how participation in warfare affects women.

Highlights

Understanding how conditions experienced during development affect reproductive timing is of considerable cross-disciplinary interest
We predict that after the war ends, younger volunteers who were exposed to higher mortality (P1) will wait less time to have a child, (P2) have shorter interbirth intervals (IBI), and (P3) higher lifetime reproductive success than their age-matched peers and sisters who are not exposed to these conditions
Results showed that girls who were exposed to higher mortality when they were younger had accelerated reproductive schedules and higher overall reproductive output after the war ended

Summary

Introduction

Understanding how conditions experienced during development affect reproductive timing is of considerable cross-disciplinary interest. Using records of Finnish women in World War II, we find that young girls serving in a paramilitary organization wait less time to reproduce, have shorter inter-birth intervals, and have more children than their non-serving peers or sisters These results support the hypothesis that exposure to elevated mortality rates during development can result in accelerated reproductive schedules and adds to our understanding of how participation in warfare affects women. In one indigenous community birth rates fell after the fall of the Soviet Union[22] suggesting that individuals may at times employ a more conservative wait-and-see strategy while absorbing information about a novel environment It remains unknown which specific cues individuals use to estimate local mortality, but some have argued that, at the psychological level, assessing this risk affects discounting rates—the relative value individuals place on present versus future rewards[8]

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