ABSTRACT
The analysis of fertility in colonizing populations is of great interest, since its individuals experience a major environmental change, and fertility rates can reflect the level of adaptation of the population to its new conditions. Using Northrop's genealogical compilations, this paper examines the fertility pattern of California's early Spanish-Mexican colonists between 1742 and 1876, their fitness levels and their trend across time throughout the colonizing period. A total of 197 women from 599 compiled families who had completed their reproductive period and had at least one child were analysed. The correlations among variables were also analysed in order to infer the relationship between longevity and fertility, and the influence of fertility determinants. The results show a natural fertility pattern, with a very young age at marriage and birth of first child (17.2 and 19.1 years respectively), and also a young age at last childbirth (38.8 years). The population's fitness showed greater values than for contemporary European populations, with 8 of 9.2 children surviving to adulthood, in comparison with 55% of newborns in Finland for the same period, suggesting a good adaptation of the population to their new environmental conditions. No relationship between fertility and lifespan was observed, as has been reported by other authors and in opposition to classical theories. A temporal trend in the number of children, consisting of three different phases, was observed, in accordance with the stability of living conditions in the region.