The Genetic effects of Immigration in a Rural Community of São Paulo, Brazil

The present work is an attempt to apply modern theoretical concepts of population genetics in the investigation of a human community.The theory of population genetics has grown rapidly through deductive-mathematical analysis, especially in consequence of the work of Fisher, Wright, Haldane, and Dahlberg.However, their theoretical conclusions have only recently begun to be checked by empirical data, mostly from human populations.The results obtained show that man is especially suitable for this kind of investigation.Human populations are not only suitable for general studies of heredity, they also illustrate some specific evolutionary problems not found in other species.One of these, undoubtedly related to culture, is the evolutionary problem of migration and intermixture between populations previously isolated one from another.The great interpopulational variability of the human species in pre-historic periods is changing toward an intrapopulational polymorphism, caused by the increasing geographical and social mobility of man.The previously existing geographical and ecological barriers are being replaced by cultural and social ones.Migration as an evolutionary factor shows a more important role than in any other species.In recent generations human migratory movements have become both larger and more generalized.Small villages and rural communities are increasing in and overlapping their new boundaries, as can be seen especially in Europe.Moreover, the past three generations have been characterized by " organized " migratory movements between remote regions, and between genetically different people, as seen especially in America.The breakdown of previously isolated communities under strong immigration pressure has not been analysed from a genetical point of view.However, these immigratory movements should be changing markedly the genetical structure of the populations.In this situation, there is likely to occur a decrease in the mean coefficient of inbreeding of these populations which will result in a relatively lower frequency of recessive abnormalities and diseases.Besides this expected eugenic effect, new gene combinations are produced and " tested ", as a result of Ricevuto il 20 II.196a.