Differential reproductive pattern in a rural Spanish region (La Cabrera, León): Consequences for potential natural selection

La Cabrera (northwest Spain), the study area, during most of the period examined (1880–1969) was characterized by high inbreeding levels and internal subdivision, which probably favoured the action of genetic drift and genetic differentiation. Indices regarding potential selection based on variables related to the reproductive pattern of reconstituted families with complete reproductive cycles (n = 1498) were analysed. A traditional demographic context, characterized by a reduction of mortality resulting in the remarkable increase of number of survivors to reproductive age, is distinguished from a recent context in which survival was similar (≈89%) and the fall of mortality and natality proportional. In general, fertility differentials (If) and martality differentials (Im) have similar values. Regarding temporal variation, Im reduces systematically, with maximum value corresponding to the first decade (1880–1899, Im = 0.493) and minimum to the last (1950–1959, Im = 0.149). If remains rather stable through...