Mechanisms of natural selection in human rural populations, survey of a Mediterranean region (La Alpujarra, SE Spain)

Abstract

SummaryMeasures of fecundity and mortality among 476 women from a Mediterranean population in SE Spain (La Alpujarra) have been used to estimate the possibilities of the action of natural selection, using Crow's Index of Total Selection. The component due to differential fecundity was twice that attributed to mortality. The Crow's index variation in different populations seems to reflect a change in the action model of evolutionary factors from a primitive situation characterized by high mortality to a new situation typified by very low fecundity. The intermediate step could be represented by the rural communities defined by a sharp decrease of mortality while fecundity remains high. The selection potential found in La Alpujarra was in the range corresponding to these rural groups.