Early-life reproduction is associated with increased mortality risk but enhanced lifetime fitness in pre-industrial humans |
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Authors: | Adam D. Hayward Ilona Nenko Virpi Lummaa |
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Affiliation: | 1Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK;2Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, UK;3Department of Environmental Health, Faculty of Health Sciences, Jagiellonian University, Krakow, Poland |
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Abstract: | The physiology of reproductive senescence in women is well understood, but the drivers of variation in senescence rates are less so. Evolutionary theory predicts that early-life investment in reproduction should be favoured by selection at the cost of reduced survival and faster reproductive senescence. We tested this hypothesis using data collected from preindustrial Finnish church records. Reproductive success increased up to age 25 and was relatively stable until a decline from age 41. Women with higher early-life fecundity (ELF; producing more children before age 25) subsequently had higher mortality risk, but high ELF was not associated with accelerated senescence in annual breeding success. However, women with higher ELF experienced faster senescence in offspring survival. Despite these apparent costs, ELF was under positive selection: individuals with higher ELF had higher lifetime reproductive success. These results are consistent with previous observations in both humans and wild vertebrates that more births and earlier onset of reproduction are associated with reduced survival, and with evolutionary theory predicting trade-offs between early reproduction and later-life survival. The results are particularly significant given recent increases in maternal ages in many societies and the potential consequences for offspring health and fitness. |
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Keywords: | ageing human reproduction trade-offs senescence life history maternal effects |
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