Inbreeding in Finland

Abstract

We have compiled data on the frequency of first-cousin marriages in Finland using royal dispensation records for the time period 1810-1872 and national population statistics for the time period 1878-1920. For the earlier period, 0.315% of Finland's marriages were contracted between first cousins (2,331 of 739,387). During the second time period, 0.174% of Finland's marriages took place between first cousins (1,325 of 761,976). These figures, which yield average kinship coefficients of 0.00020 and 0.00011, respectively, show that the level of inbreeding in Finland due to first-cousin marriage has been quite low. An analysis of individual parishes shows that first-cousin marriages are, on average, substantially less frequent than predicted by a random-mating model. In order to evaluate determinants of first-cousin marriage, several predictive variables have been examined: parish ethnic composition (proportion of Swedish and Finnish speakers), husband's occupation (graded into 6 socioeconomic levels), geographic distance between spouses' premarital residences, population density, parish endogamy, and urban vs. rural residence. Various logistic and linear regression models were analyzed in which consanguinity was the dependent variable. The best predictors of consanguinity were ethnic composition and occupation. The other variables were not in general significant predictors. These results show that many of the "mate availability" factors that would be predicted theoretically to account for consanguinity variation (population density, geographic isolation, urban vs. rural residence) do not. Instead, the best predictors of consanguinity at the first-cousin level are cultural factors such as ethnicity and occupation. Evaluation of cultural variables can provide a greatly enriched interpretation of complex biosocial phenomena such as inbreeding.

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

“…Inbreeding patterns in Guipú zcoa are rather similar to those recorded for other Basque territories in comparable periods of time (e.g., Alava; Calderón et al, 1993), and fit closely into the basic model of secular evolution of inbreeding recorded in other large Western European populations (Sutter and Tabah, 1948;Twiesselman et al, 1962;Moroni, 1967;Saugstad, 1977;McCullough and O'Rourke, 1986;Jorde and Pitkä nen, 1991). By contrast, in most Iberian populations, the decrease in inbreeding appears 3-4 decades later, coinciding with the takeoff of large-scale industrialization in Spain (PintoCisternas et al, 1979;Calderón, 1989;Gómez, 1989;Morales, 1992;Fuster et al, 1996).…”

“…Consanguinity studies in small and large populations of the Basque area confirmed that the rates of close consanguineous matings (uncle-niece/auntnephew and first cousins) are unusually high in comparison to most Iberian and Western European population standards (Sutter and Tabah, 1948;Moroni, 1967;Pettener, 1985;Calderón, 1989;Jorde and Pitkä nen, 1991). In contrast to this pattern, mean inbreeding levels registered over a long time span in the Spanish Basque Country are not particularly high, except for some local populations (Abelson, 1978;Zudaire, 1981;Alfonso-Sá nchez et al, 1997;Peñ a et al, 2002).…”

The Influence of Past Endogamy and Consanguinity on Genetic Disorders in Northern Sweden

“…Within northern Scandinavia, studies based on royal dispensation records and national population statistics show a very low level of first cousin marriage in Finland during the 19th century, although, as in northern Sweden, parishes with a substantial Saami population were an exception (Jorde & Pitkänen, 1991). Avoidance of first cousin marriage appears to have resulted both from the requirement for royal dispensation payments, which continued in Finland until 1872, and a cultural prohibition in parts of eastern Finland against paternal parallel cousin marriages (Jorde & Pitkänen, 1991).…”

“…Avoidance of first cousin marriage appears to have resulted both from the requirement for royal dispensation payments, which continued in Finland until 1872, and a cultural prohibition in parts of eastern Finland against paternal parallel cousin marriages (Jorde & Pitkänen, 1991). The latter prohibition may have stemmed from the restrictions on cousin marriage applied by the Christian Orthodox Church, which would have been quite influential in regions of the country bordering on Russia (Ignatius, 1994(Ignatius, -1995.…”

A study of contemporary levels and temporal trends in inbreeding in the Tangier Island, Virginia, population using pedigree data and isonymy

“…Inbreeding is by no means limited to small isolates; low levels of inbreeding have also been observed in large "open" populations (Cavalli-Sforza and Bodmer, 1971;McCullough and O'Rourke, 1986;Czeizel et al, 1976;Jorde and Pitkanen, 1991;Dahlberg, 1938;Sutter and Goux, 1962;Woolf et al, 1956). Scientific interest, however, has been focused on smaller, more isolated populations wherein inbreeding has been found to be associated with a pronounced incidence of recessive disorders (Bailit et al, 1966;Hussels, 1969;Ghosh and Majumder, 1979;Pollock et al, 1972;O'Brien et al, 1988;Khoury et al, 1987).…”