Ecology, 91(12), 2010, pp. 3515–3525 Ó 2010 by the Ecological Society of America Food availability at birth limited reproductive success in historical humans IAN J. RICKARD, 1,7 JARI HOLOPAINEN, 2 SAMULI HELAMA, 3 SAMULI HELLE, 4 ANDREW F. RUSSELL, 5,6 AND VIRPI LUMMAA 1 1 Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN United Kingdom 2 Department of Geosciences and Geography, University of Helsinki, P.O. Box 64, Helsinki FIN-00014 Finland 3 Arctic Centre, University of Lapland, P.O. Box 122, Rovaniemi FIN-96101 Finland 4 Section of Ecology, Department of Biology, University of Turku, Turku FIN-20014 Finland 5 Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Penryn Cornwall TR10 9EZ United Kingdom 6 La Station d’Ecologie Experimentale du CNRS a ` Moulis, Moulis 09200 France Abstract. Environmental conditions in early life can profoundly affect individual development and have consequences for reproductive success. Limited food availability may be one of the reasons for this, but direct evidence linking variation in early-life nutrition to reproductive performance in adulthood in natural populations is sparse. We combined historical agricultural data with detailed demographic church records to investigate the effect of food availability around the time of birth on the reproductive success of 927 men and women born in 18th-century Finland. Our study population exhibits natural mortality and fertility rates typical of many preindustrial societies, and individuals experienced differing access to resources due to social stratification. We found that among both men and women born into landless families (i.e., with low access to resources), marital prospects, probability of reproduction, and offspring viability were all positively related to local crop yield during the birth year. Such effects were generally absent among those born into landowning families. Among landless individuals born when yields of the two main crops, rye and barley, were both below median, only 50% of adult males and 55% of adult females gained any reproductive success in their lifetime, whereas 97% and 95% of those born when both yields were above the median did so. Our results suggest that maternal investment in offspring in prenatal or early postnatal life may have profound implications for the evolutionary fitness of human offspring, particularly among those for which resources are more limiting. Our study adds support to the idea that early nutrition can limit reproductive success in natural animal populations, and provides the most direct evidence to date that this process applies to humans. Key words: birth weight; cohort effect; delayed life-history effects; fetal growth; fetal programming; life-history evolution; maternal effect; parental investment; reproductive development; silver spoon. INTRODUCTION The environmental conditions that animals experience during development affect their reproductive perfor- mance and, ultimately, their fitness (Lindstro¨m 1999, Metcalfe and Monaghan 2001, Lummaa and Clutton- Brock 2002). Knowledge of these individual-level effects is essential for an understanding of the population-level consequences of environmental change in wild animals (Beckerman et al. 2002), as well as the selective forces that shape species’ plastic responses to the environment (West-Eberhard 2003). One of the specific factors likely to be important in influencing individual fitness in early life is nutrition. A small number of laboratory (Meikle and Westberg 2001, Zambrano et al. 2005, Guzma´n et al. 2006) and field (Descamps et al. 2008) studies of mammals have provided direct evidence that the supply of resources to individuals during development eventu- ally constrains adult reproductive performance. In general, however, the role of nutrition in these processes in natural populations must be inferred through proxies such as population density and climate recorded in the early life of cohorts (Forchhammer et al. 2001, Reid et al. 2003). Human populations represent potentially valuable sources of data for investigating the effects of early nutrition, because food supply and reproductive output can potentially be determined at an individual level. Two approaches have typically been used to examine reproductive performance in relation to early-life environment. The first has been to examine the predictive power of indirect measures of the intrauterine environment, such as birth weight or gestational age (estimated time from conception to birth) (Ekholm et al. 2005, Main et al. 2006, Nohr et al. 2009). However, interpretation of these associations in the context of nutritional supply to the fetus is far from simple (Wells 2006). Nohr et al. (2009) found that women with Manuscript received 5 January 2010; revised 22 April 2010; accepted 4 May 2010. Corresponding Editor: F. S. Dobson. 7 E-mail: i.rickard@sheffield.ac.uk 3515