1. Evolutionary ecology of human birth sex ratio under the compound influence of climate change, famine, economic crises and wars
- Author
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Samuli Helama, Kalle Lertola, and Samuli Helle
- Subjects
Male ,Warfare ,Offspring ,Climate Change ,Population Dynamics ,Biology ,History, 21st Century ,Human sex ratio ,03 medical and health sciences ,0302 clinical medicine ,Humans ,Sex Ratio ,Selection, Genetic ,Finland ,Ecology, Evolution, Behavior and Systematics ,030304 developmental biology ,2. Zero hunger ,0303 health sciences ,030219 obstetrics & reproductive medicine ,Ecology ,Stressor ,History, 19th Century ,History, 20th Century ,Population ecology ,Biological Evolution ,Infant mortality ,Starvation ,13. Climate action ,Cohort ,Famine ,Female ,Animal Science and Zoology ,Sex ratio ,Demography - Abstract
1. Human sex ratio at birth at the population level has been suggested to vary according to exogenous stressors such as wars, ambient temperature, ecological disasters and economic crises, but their relative effects on birth sex ratio have not been investigated. It also remains unclear whether such associations represent environmental forcing or adaptive parental response, as parents may produce the sex that has better survival prospects and fitness in a given environmental challenge. 2. We examined the simultaneous role of wars, famine, ambient temperature, economic development and total mortality rate on the annual variation of offspring birth sex ratio and whether this variation, in turn, was related to sex-specific infant mortality rate in Finland during 1865-2003. 3. Our findings show an increased excess of male births during the World War II and during warm years. Instead, economic development, famine, short-lasting Finnish civil war and total mortality rate were not related to birth sex ratio. Moreover, we found no association between annual birth sex ratio and sex-biased infant mortality rate among the concurrent cohort. 4. Our results propose that some exogenous challenges like ambient temperature and war can skew human birth sex ratio and that these deviations likely represent environmental forcing rather than adaptive parental response to such challenges.
- Published
- 2009
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