Does the institutional environment shape human life-histories? The historical case of Augustus Smith and the Isles of Scilly

Human behavioural ecologists use life-history theory to explain variation innatality and mortality. Social policy is often deployed to improve human health ormediate access to resources, extending lifespans and affecting the timing andcosts of reproduction, and hence is likely to shape human life-histories. Here, weused historical policy changes introduced on the Isles of Scilly in the early 1800s,aimed at increasing education, employment, and food availability, to assesswhether such changes in the institutional environment increased mean lifespan,reduced mean family size or lowered child mortality. To do so, we usedinterrupted time series analysis, commonly used in impact evaluation, andgeneralised additive models, to model non-linear time series data. We foundsome evidence that a reduction in child mortality was associated with the policychanges, but lifespan increased independently throughout the study period andfamily size declines largely predated the interventions. Hence, while the policychanges are likely to have improved standards of living, the life-historyconsequences of these changes to the institutional environment are less clear.We discuss the relative merits of the two analytical approaches and how adoptingmultiple methodologies increases transparency of the full range of plausibleresults.