Hereditary disorders in the French Canadian population of Quebec. II. Contribution of Perche.

In our previous paper (De Braekeleer and Dao 1994) we showed that most of the hereditary disorders present in the French Canadian population of Canada cluster in eastern Quebec. Furthermore, the disorders probably were brought to Nouvelle-France in the seventeenth century by migrants coming from Perche, France. Here, the analysis of several historical, social, and demographic factors shows that, rather than migrants coming from other French provinces, migrants from Perche came from a limited area and settled in eastern Quebec, preferentially on the north shore of the St. Lawrence River. They arrived earlier than the other migrants and had a larger descendance. However, only a limited number of migrants from Perche were found in the founding nucleus of the hereditary disorders. Further analysis shows that the social system had major consequences on migration, marriage, kin network, and family behavior. Therefore the presence and the high frequency of most of the hereditary disorders in the French Canadian population appear to be the result of founder effect and genetic drift.