Demographic structure of a transplanted Tlaxcalan population in the Valley of Mexico

Abstract

This research explores the evolutionary consequences of the transplantation and subsequent demographic adaptation of Cuanalan, a migrant population in the Valley of Mexico. Through comparisons with historical and contemporary populations from the area of origination—the state of Tlaxcala—an attempt is made to reconstruct the demographic and evolutionary changes which have occurred in the splinter population over the past four centuries. Both demographic and preliminary genetic data indicate that Cuanalan is a hybridized population. About two-thirds of marriages of Cuanalan-born individuals are endogamous. Average number of liveborn children for prolific women over 40 is 6.5. Since 1866, mean age at death in the community is 20.8 years, and the infant death rate is 30%. Major causes of death are respiratory diseases, gastrointestinal disorders, and childhood infections. The high variance in completed fertility and high pre-reproductive mortality indicate a continuation of conditions making for the rapid action of natural selection which have historically characterized Tlaxcalan populations. Genetic drift was probably an important factor in the early differentiation of the migrant population. The data suggest that the evolutionary divergence of Cuanalan from the Tlaxcalan gene pool has been rapid and extensive.