Demography and genetic structure of the Welch settlement in Patagonia. 1865-1920
The demographic and the genetic structures of the Welch colony in the Chubut , are studied from the reconstruction of the migration flow, from 1865 to 1920. Three transversal cuts in the demographic development are analysed: (1) in 1876 at the favour of a first census, shortly after the arrival of the second contingent of settlers; (2) in 1895, at the favour of a second census when most of the migration is over; (3) in 1920, when the population begins to interact with non Welch settlers. At each step of the process are observed the demographic components and estimated the genetic contributions to the collective gene pool of the distinct groups of settlers. In broad lines, the primary demographic structure, typical of migrating colonists, with a large excess of young male, slowly evolves to the second period and still more to the third toward the classical structure of rural populations, with balanced sex components and a younger age structure. The genetic contribution of the 1865 founders is not predominant, insofar as only 80 among the 153 first immigrants had progeny. As a consequence of the high geographical diversity of recruits to colonize the Chubut, no consanguinity is observed during the whole period, all marriages being contracted between unrelated persons.