Supplementary Code: Natural Selection on Reproductive Timing Varies by Education in 20th-century Estonia

This dataset contains individual-level reproductive and socioeconomic information for Estonian citizens born between 1925 and 1977 who survived to at least age fifteen. For every person the file lists sex, year of birth, total number of children born up to 2022, and the birth years of the first and last child. Self-reported educational attainment is available for the majority of individuals and is recorded in five categories ranging from primary to tertiary education. Analysis of these records shows that women with only primary education consistently realised the largest completed family sizes across the entire birth-year range examined. Among men a positive association between education and reproductive success emerged in cohorts born after the early 1950s, so that tertiary-educated men eventually out-reproduced their less-educated peers despite delaying parenthood. Educational differences in the timing of reproductive events were also pronounced. Women with primary education both entered parenthood earliest and experienced the strongest directional selection favouring an early first birth, whereas the same education group in men displayed the shortest interpregnancy intervals and the fastest overall reproductive tempo. Stabilising selection on intermediate interbirth intervals was strongest among parents with minimal schooling, yet these men and women were likewise subject to selection favouring a late cessation of reproduction. Despite that pressure, fathers with primary education were generally the first to terminate childbearing. Taken together, the dataset demonstrates that selection on reproductive timing has been consistently stronger in the lowest educational strata and that temporal trends in reproductive schedules do not simply mirror the selective forces acting on recent generations. The files therefore offer a resource for investigating how social stratification intersects with natural selection in a contemporary human population.