Inbreeding levels and consanguinity structure in the Basque province of Guipúzcoa (1862-1980)

Abstract

This work analyzes the spatial heterogeneity of consanguinity in the Basque province of Guipúzcoa (Spain), using data provided by Catholic dispensations (1862-1980). Secular trends in consanguinity rates (%M(C)) and mean inbreeding coefficient (F) were similar in the seven Guipúzcoan regions considered, with peaks between 1881-1920 and subsequently a gradual decline. Substantial differences in consanguinity characteristics emerged when the regions were classified according to level of urbanization. Principal component analysis (accounting for more than 85% of the total variance in consanguinity variables) clearly discriminated between urbanized and less urbanized regions. The latter stand out for their high consanguinity rates (3.57-6.73%), mean inbreeding coefficient (0.00112-0.00240), and M22/M33 ratio (M22, first cousins; M33, second cousins), which ranged between 0.89-1.48. Moreover, in less urbanized regions, marital consanguinity was eminently local, and mainly conditioned by regional endogamy (71.4-85.0%). By contrast, urban subpopulations showed the lowest consanguinity rates (1.60-1.96%) and mean inbreeding coefficient (around 0.0007). In these regions, the M22/M33 ratio also exhibited high values (1.07-1.56), but this time at the expense of the contribution of the immigrant group. Discussion of the factors that could have modeled this spatial variation in consanguinity centers on: 1) demographic aspects related to the chronology and intensity of industrialization, 2) the geography of the territory and the geography of peopling, and 3) linguistic differences, expressed in the uneven distribution of Basque-speakers among the different territories considered.

The Expanded mtDNA Phylogeny of the Franco-Cantabrian Region Upholds the Pre-Neolithic Genetic Substrate of Basques

“…In fact, some authors have argued that the Basque language itself has contributed to the genetic isolation of the Basques [10], [47]. The uniqueness of the deeply-rooted sociocultural features of the Basques, notably their singular language, has been argued to be crucial in the high endogamy levels and high consanguinity rates that characterize the autochthonous Basque population [48], [49], thus contributing to their genetic isolation from neighboring human groups.…”

Ancestry markers from the human chromosome 6: Alu repeats from the MHC in autochthonous Basques

“…Indeed, some authors suggest that the genetic distinctiveness of the Basques might be mainly determined by population isolation associated with their singular language [29,30], bearing in mind that linguistic differences can be effective barriers to gene flow and panmixis [39]. Thus, the Basques constitute a special case of European population where consanguineous matings, closely related to deeply-rooted sociocultural practices, have been an important component of the marital structure [13,14]. Overall, it seems clear that genetic drift and high inbreeding levels associated with population isolation have played a major role in the modeling of the genomic singularity of the autochthonous Basque groups.…”

“…The samples for this study were collected from the autochthonous population settled in the northern fringe of Navarre province and in Guipuzcoa province, both located in the historical Basque area. Both these zones were selected mainly because North Navarre and Guipuzcoa are the two Basque regions possessing the highest density of Basque speakers (Euskaldunes) of any Iberian or French Basque territory, and therefore the Basque language (Euskera) still shows great vitality there [13]. More specific details concerning geography, demography and linguistic characteristics of these two Basque regions can be consulted in previous works [13][14][15][16].…”

Genetic variability in autochthonous Basques from Guipuzcoa: a view from MHC microsatellites

“…, 2001). The Basques constitutes a singular case of European population where consanguineous matings, closely related to deeply rooted sociocultural mores, have been an important component of the marital structure (Alfonso‐Sánchez et al. , 2001, 2005).…”

“…This is likely the reason why the Basque language ( Euskera ) still shows great vitality there. Further detailed information on the Basque province of Guipuzcoa (territory and geography, history, modern and contemporary demography, linguistics) can be consulted in a previously published work (Alfonso‐Sánchez et al. , 2005).…”