Secondary sex ratio variation during stressful times: The impact of the French Revolutionary Wars on a German parish (1787–1802)
Article first published online: 12 OCT 2006
Copyright © 2006 Wiley-Liss, Inc.
American Journal of Human Biology
Volume 18, Issue 6, pages 806–821, November/December 2006
How to Cite
Kemkes, A. (2006), Secondary sex ratio variation during stressful times: The impact of the French Revolutionary Wars on a German parish (1787–1802). Am. J. Hum. Biol., 18: 806–821. doi: 10.1002/ajhb.20562
- Issue published online: 12 OCT 2006
- Article first published online: 12 OCT 2006
- Manuscript Accepted: 18 JUN 2006
- Manuscript Revised: 5 MAY 2006
- Manuscript Received: 28 FEB 2006
The observation that declines in the human secondary sex ratio (SSR) may be linked to stressful periconceptional periods has received considerable attention (Catalano  Hum Reprod 18:1972–1975; Catalano et al.  Int J Epidemiol 34:944–948,  Hum Reprod 20:1221–1227,  Paediatr Perinat Epidemiol 19:413–420). For the purpose of testing the external validity of this phenomenon, birth records from four German village genealogies (N = 1,048) were analyzed to study the impact of the French Revolutionary Wars (1787–1802) on the proportion of male births. All births were subdivided into three cohorts (prewar, 1787–1792; war, 1792–1797; and postwar, 1797–1802). Differences in SSR between cohorts achieved statistical significance (χ2 = 7.695; df = 2; P = 0.021). In addition, changes in SSR before, during, and after the wars were monitored by risk analysis. Using the SSR of the prewar period as a control, the results of the war cohort failed to achieve statistical significance (regression coefficient, −0.257; Exp(B) = 0.773; P = 0.118), while the odds reduction of 32.3% in the postwar period proved to be statistically significant (regression coefficient, −0.390; Exp(B) = 0.677; P = 0.006). It is hypothesized that the experience of postwar economic hardship (attributable to lowered food availability paired with dietary changes) represents the most likely proximate cause. The study also finds evidence of a parental sex ratio manipulation strategy meant to offset the female-biased SSR after the wars. It is argued that from an evolutionary perspective both the decline in SSR in response to stress as well as parental manipulation of the tertiary sex ratio convey reproductive advantages. Am. J. Hum. Biol. 18:806–821, 2006. © 2006 Wiley-Liss, Inc.