Consanguinity in two Spanish regions: La Cabrera and Fuentes Carrionas. Dispensations and isonymy

In this work the level and structure of consanguinity is analysed in two Spanish rural regions of similar geographic and orographic characteristics for the period between 1880 and 1979, employing two different methodologies. The estimates according dispensations shows that the total levels (alpha4 = 0.00552 in La Cabrera and 0.00405 in Fuentes Carrionas) and the structures of consanguinity (C22/C33 = 0.43 and 0.34) are similar in both regions, but have evolved differently. Whereas in La Cabrera both parameters have remained stable, in Fuentes Carrionas they fluctuated through the period analysed. On studying the structure of consanguinity more closely using the isonymic method, it can be seen that in La Cabrera total consanguinity (Ft = 0.0206) should be attributed mainly to environmental factors (Fr = 0.0193) and to a lesser extent to socio-cultural factors (Fn = 0.0013), whereas in Fuentes Carrionas it derives, almost exclusively, from the former (Ft = 0.01270; Fr = 0.01589; Fn = -0.00325).