Isolation and marriage patterns in four South Tyrolean villages (Italy) during the nineteenth century

No information is currently available on the marriage patterns of German-speaking communities of the South Tyrol area. The aim of this study is to investigate the reproductive isolation of four South Tyrolean mountain villages during the 19th century. Data about 3953 marriages were drawn from existing pedigrees and completed with data from the parish registers of the studied villages to calculate the following indicators: age at marriage, endogamy, inbreeding from dispensations and from isonymy and repeated pairs of surnames among couples. The results show high levels of endogamy (78-87%) and an elevated age at marriage in all the studied villages. The percentages of consanguineous marriages (10-33%) vary considerably but result overall in relatively low inbreeding values (alpha 0.0015-0.0036; Ft 0.0098-0.0138). Levels of endogamy are consistent with the geographic characteristics of the area, while inbreeding values are lower than those observed in previous studies on Alpine communities. This is due to a low frequency of marriages between close relatives, probably related to the peculiar demographic and cultural characteristics of the studied populations that differentiate them from neighbouring Italian-speaking villages.     

Inbreeding in Southeastern Spain

In this paper, the structure of a southeastern Spanish population was studied for the first time with respect to its inbreeding patterns and its relationship with demographic and geographic factors. Data on consanguineous marriages (up to second cousins) from 1900 to 1969 were taken from ecclesiastic dispensations. Our results confirm that the patterns and trends of inbreeding in the study area are consistent with those previously observed in most non-Cantabrian Spanish populations. The rate of consanguineous marriages was apparently stable between 1900 and 1935 and then sharply decreased since 1940, which coincides with industrialization in Spain. A marked departure from Hardy-Weinberg expectations (0.25) in the ratio of first cousin (M22) to second cousin (M33) marriages in the study population (0.88) was observed. The high levels of endogamy (>80%) and its significant steadiness throughout the twentieth century is noteworthy. Accordingly, our results show that exogamous marriages were not only poorly represented but also that this reduced mobility (<6 km) suggests that the choice of a mate was preferentially local. We found higher mobility in M22 with respect to M33 cousin mating. The relationships between population size and consanguinity rates and inbreeding fit power-law distributions. A significant positive correlation was observed between inbreeding and elevation. Many Spanish populations have experienced a prolonged and considerable isolation across generations, which has led to high proportions of historical and local endogamy that is associated, in general, with high \( \overline{F} \) values. Thus, assessing genomic inbreeding using runs of homozygosity (ROH) in current Spanish populations could be an additional pertinent strategy for obtaining a more refined perspective regarding the population history inferred from the extent and frequency of ROH regions.     

Trends in inbreeding, isonymy, and repeated pairs of surnames in the Valserine Valley, French Jura, 1763-1972

The estimates of inbreeding derived from pedigrees and frequency of isonymous marriages (i.e., between persons of the same surname) are compared using genealogical and isonymic information from 4,899 marriages recorded between 1763 and 1972 in 4 rural villages of the French Jura region (a mountainous area near the Swiss border). Before the second half of the 20th century, the two kinds of estimates show a different temporal evolution. The mean inbreeding coefficient based on pedigrees increases between 1763 and 1852 and reaches a maximum between 1853 and 1882 (alpha = 0.0028), with a very low percentage (< 1%) the result of remote kinship. The mean inbreeding coefficient based on isonymy is always higher, with a maximum observed between 1793 and 1822 (F = 0.0200), and it remains roughly the same between 1763 and 1882 (F = 0.0150), with a high percentage resulting from a random component (Fr), a consequence of the small population size and genetic drift. After 1883, the 2 mean coefficients decrease. This discordance is largely explained by the poor quality, for the first periods, of the genealogical data base, which ignores the more remote links of kinship, justifying the use of the model of Crow and Mange (1965) to explore consanguinity during the more ancient periods. The temporal evolution of the repeated pairs of surnames index (RP) confirms the recent evolution of the marital structure of the valley. Moreover, it appears that isonymous marriages and repeated and unique pairs of surnames constitute 3 distinct matrimonial groups characterized by both a different mean coefficient of inbreeding (alpha) and a different rate of endogamy.     

Inbreeding as measured by isonymy in two Venezuelan populations and its relationship to other variables

Isonymy is a useful approach to the study of population structure and thus can be utilized to detect deviations from random mating. In this study we give the results of an analysis of inbreeding levels and relate such variables as mean marital distance, surnames repeated in isonymous couples, and percentage of people using only maternal surnames to inbreeding and endogamy in two Venezuelan populations of black ancestry, Birongo and La Sabana. These populations differ in their sociocultural development and degree of isolation. We estimated inbreeding through isonymy and directly from genealogy. The most important findings are that the Ft values are higher than the a's, that the Fn component of Ft is higher than the Fr component, and that there is higher endogamy, inbreeding, and isolation in Birongo than in La Sabana. These results are in agreement with the sociocultural and historical background and development of each population. Nevertheless, both populations show similar temporal trends in almost all the variables analyzed. The use of isonymy as a complementary tool to study population structure is proposed, especially for Ibero-American populations.     

Biodemographic study of a central Apennine area (Italy) in the 19th and 20th centuries: marriage seasonality and reproductive isolation.

This study investigates seasonality of marriages and reproductive isolation in six long-isolated communities in the central Apennines (Italy). It had two objectives: (1) the identification of an Apennine biodemographic model in comparison with mountain communities of other regions, and with non-Apennine communities in Abruzzo, and (2) to identify the possible effects of the drainage of Lake Fucino (1854-1876) on that area. Marriages in this region show two very stable seasonal patterns: one is typical of sedentary rural societies, with summer migrations and marriages preferentially celebrated in the winter, and the other has marriages that are strongly concentrated in the summer months, i.e. between 75% and 93.5% of marriages were celebrated between June and October in these communities in the 1800s. These were traditionally pastoral communities with winter transhumance of the flocks and their shepherds towards the lowlands of southern Italy. In both groups, restrictions imposed by the Catholic Church do not seem to have affected the timing of marriages. Indeed, economic factors related to work activities seem to have had more influence. Concerning reproductive isolation, the results show high rates of endogamy: between 85% and 98% in both the 19th and 20th centuries. Rates of consanguineous marriages were between 5% and 20%, and those of isonymous marriages rarely exceeded 9%. The coefficient of inbreeding a shows that there was a delayed, limited period of increased consanguinity in the few decades around the turn of the century. This is different from the national situation, and thus could be a consequence of the Lake Fucino drainage.     

Isonymic analysis of population structure in Gredos, Spain

For the period 1875-1975 an isonymic analysis was made based on 41,696 marriages celebrated in three valleys (Tormes, Alberche and Tietar) from Gredos (Spain). Total inbreeding (Ft) was lower in the Tietar valley (0.0103- 0.0136), followed by the Tormes (0.0125-0.0255) and the Alberche (0.0153-0.0200). In the latter, random inbreeding (Fr) surpassed non random (Fn). Correlation coefficients were obtained to confirm an association of inbreeding from isonymy with valley and village endogamy rates, locality census, altitude, and alpha inbreeding. Fn correlated positively with average valley endogamy and village endogamy and with altitude, but inversely with census size. Contrarily, Fr related significantly to village endogamy. The non-random component from isonymy related positively to inbreeding from dispensations. Except for village endogamy, both variables show the same relationships to variables, such as altitude, which reflect limitations to mobility; or valley endogamy indicating the disposability of potential mates which in turn depends on the census size.     

Genetic demographic characteristics of the rural population of the Tuva Republic: marriage structure and inbreeding]

Marriage structure was studied in three rural populations of the Tuva Republic: the Shinaan population and the populations of Todzhinskii and Bai-Taiginskii raions (districts). The Shinaan and Bai-Taiginskii populations had high levels of endogamy (0.6704 and 0.6050, respectively). In the Todzhinskii population, which was characterized by a mixed ethnic composition, endogamy was 0.3779 for the total population and 0.4626 for Tuvinians; interethnic marriages in this population were rare. The values of marriage assortativeness with respect to birthplace were 19.38, 40.75, 75.87, and 41.87% in the Shinaan, Bai-Taiginskii, all the Todzhinskii populations, and Tuvinian monoethnic marriages in the Todzhinskii raion, respectively. High marriage assortativeness with respect to ethnicity was found. Its values (A') were 91.85 and 93.49% in Tuvinians and Russians, respectively. Tuvinian populations were characterized by high inbreeding. The total (F(it)), random (Fst), and nonrandom inbreeding (Fis) estimated by isonymy were 0.004237, 0.002298, and 0.001944 in the Shinaan population, 0.007292, 0.009448, and -0.002177 in the Bai-Taiginskii population, and 0.003846, 0.004152, and -0.000307 in the Todzhinskii population, respectively (in the latter populations, the F(it), Fst, and Fis values for Tuvinian marriages alone were 0.005000, 0.007222, and -0.002238, respectively). The results obtained indicate that individual territorial groups of Tuvinians retain a high degree of genetic isolation from one another.     

Inbreeding in Finland

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 patterns in La Cabrera, Spain: dispensations, multiple consanguinity analysis, and isonymy

Marital structure and inbreeding coefficients were analyzed in La Cabrera, an isolated mountain region in northwestern Spain. A total of 5,714 marriages were celebrated from 1880 to 1989 in the 37 parishes of the area. The total frequency of consanguineous marriages (up to the fourth degree) is 23.05%; multiple consanguineous marriages are remarkably common, reaching 5.43% of the total. The first cousin/second cousin ratio (referred to as kinship-type frequencies) is 0.43. The inbreeding values are the highest recorded in Spain and in Europe: alpha3 is 4.82 x 10(-3) for the whole period and alpha4 is 6.78 x 10(-3) for 1880--1919. The temporal trend of inbreeding shows high values (alpha3 > 4.5 x 10(-3)) for a particularly long period (1900--1959) and a rapid decline from 1960 onward. This historical inbreeding trend is clearly related to changes in population size. The frequencies of multiple consanguineous marriages and the analysis of isonymy show that the inbreeding structure is related to geographic and demographic factors. Comparing the results at two hierarchical levels (La Cabrera as a whole and the 37 parishes individually), we conclude that the inbreeding values are affected by internal geographic subdivision of the population (Wahlund effect). Social and cultural factors, such as avoidance of or preference for consanguineous marriages, are less important but depend on the kinship type involved.     

Trends of consanguineous marriages in a Sunni Muslim population of West Bengal, India

The Muslim population of the Chaltaberia village in the district of South 24 Parganas in West Bengal is divided into several wards (paras) inhabited by people of specific surnames. The frequency of endogamous marriages within surnames is greater than randomly expected ones. An incomplete reproductive isolation is observed among the five dominant surnames. Consanguineous marriages occur more often outside the village than inside. Leaving out marriages between long distances, a small median distance of 6.36 km is recorded. The neighborhood area works up to be 552.2 km2, which is rather small. There is an underlying process of breeding isolation by distance. A generation length of 21 years has been used for examining the temporal change in consanguineous marriages and inbreeding, which generally appears to increase. There is a general trend of decline in consanguineous marriages towards the southern part of West Bengal and eastern part of Assam among the Bengalee Muslims. The frequency of consanguineous marriages is 7.3% out of all marriages (N=1153) that have taken place in six generations in the population. The first cousin marriage is nearly 50% of all marriages. Patrilineal marriages are common in marriages between second and third cousins. An increase of consanguineous marriages in the younger generation was observed, but the total frequency agrees with a general trend of a decline in the frequency of consanguineous marriages among the Muslims in this part of India.     

Population and demographic study of the Turkmen Tekke

Genetical and demographic studies of typical rural population of Turkomen teke in Yangi-Kala village of the Ashkhabad region (about 5.000 inhabitants) were performed through the examination of a sample of 3528 persons. The population is characterised by intensive growth (mean number of children per one woman is 6.17), a high level of endogamy (the total coefficient of inbreeding being 0.010912), preserving the traditional marriage system (91.9 and 8.1% of intrageneric and intergeneric marriages, respectively). Migration does not significantly influence endogamy, because it takes place among kin families.     

Medicogenetic study of isolates in Uzbekistan. I. Statement of the problem and characteristics of the groups studied]

The paper comprises results of studying some demographic and populaton characteristics of the inhabitans of the Samarkand region as a whole and two villages, Karakent and Ishan, inhabited with Uzbeks-Khoja, a special religious-social caste in the past. It is shown that 87.4% of marriages in the Samarkand region are of international character (the information has been obtained on 7995 married couples). The frequency of consanguineous marriages is 11.6%, and among them 40.5% are first-cousin marriages and 39.1% are marriages of remote relatives. The coefficients of inbreeding are rather high among the Jewish, Tajik and Uzbek communities. The coefficient of inbreeding as a whole is F=0.0042 in this region and approaches to the maximal level, characterizing a panmix population. The average size of a family in the villages of Karakent and Ishan is approximately 4.0 persons. The values of reproductive performance, the nature of termination of pregnancies do not differ from those of panmix population. The percentage of intravillage and consanguineous marriages are 56% and 12.5% for the first village, and 25% and 2% for the second one respectively. The coefficient of inbreeding for karakent is F=0.0064, for Ishan--F=0.0014. Taking into consideration the historical development of the two villages and the cumulative data, the conclusion is drawn that Karakent is an isolate on a religious ground whereas Ishan is a disintegrated isolate.     

Evolution of marital structure in 20 Sardinian villages from 1800 to 1974

This paper reports the data for endogamy, exogamy and consanguinity in 20 Sardinian villages from 1800 to 1974, divided into generational periods (25 years). The data are taken from the records of 48,262 marriages celebrated in the parishes of 20 Sardinian villages. The results for Spearman's rank correlation coefficient indicate significant positive correlations of endogamy with consanguinity (r(s) = 0.6551, percentage of consanguineous marriages; r(s) = 0.5477, Bernstein's alpha), with altitude (r(s) = 0.6386), with population size (r(s) = 0.2519), as well as a significant negative correlation of endogamy with time (r(s) = -0.4210). In addition, consanguinity shows a significant positive correlation with altitude (r(s) = 0.5717, percentage of consanguineous marriages; r(s) = 0.6295, Bernstein's alpha) and a significant negative correlation with time (r(s) = -0.2363, percentage of consanguineous marriages); the negative correlation between the mean level of consanguinity (alpha) and time is statistically not significant. In the single parishes, the levels of endogamy and consanguinity are generally higher in the mountain villages than in those situated in the hill and plain areas. Finally, it is hypothesized that, in the time period considered, the level of consanguinity and especially of endogamy were largely determined by isolation.     

Inbreeding in Gredos mountain range (Spain): contribution of multiple consanguinity and intervalley variation.

The present paper examines consanguineous marriages occurring between 1874 and 1975 in three valleys (Tormes, Alberche, and Tiétar) in the Sierra de Gredos mountain range, Avila province, Spain. Information was obtained from parish registers of 42 localities, corresponding to a total of 41,696 weddings. Consanguineous marriages were defined as those up to the third degree of consanguinity (second cousins). From 1874 to 1975 the percentage of related mates was 4.45% and the inbreeding coefficient was 0.0011868 (for 1874 to 1917 corresponding figures up to the fourth degree were 16.44% and 0.00 19085, respectively). In order to ascertain the characteristics and evolution of mating patterns in Gredos, the contribution of each degree of kinship was analyzed as a whole and then for each valley separately. Regarding total consanguineous marriages in Gredos, there is a low frequency of uncle-niece matings (0.21%) and a first-second cousin mating ratio (C22/C33) of 0.23 (up to the third degree of consanguinity). Before 1918 multiple matings (i.e., those involving more than a single relationship) accounted for 19.16% of consanguineous marriages (up to the fourth degree). The observed frequencies of multiple consanguineous marriages was, on average, about twice that expected at random, and the proportion of such marriages to total inbreeding was 34.65%. The temporal change of the Gredos inbreeding pattern was characterized by a recent decrease; the highest inbreeding levels correspond to the period from 1915 to 1944. Finally, intervalley differences (maximum inbreeding coefficient in the Tormes, minimum in the Tiétar) are interpreted considering the geography, population size, and population mobility for each valley     

Genetic demographic description of the Ust-Aldan rural population of Sakha Republic (Yakutia): migrations and marriage structure

Migrations, dynamics of the gametic structure of rural populations, and marriage structure with respect to birthplaces and inbreeding estimated from isonymy have been studied in the Ust-Aldan ulus (administrative district) of Sakha Republic (Yakutia). The villages studied (Byadi, Dyupsya, and Cheriktey) are characterized by intense migration; however, the migration radius is small (most migrations occur within the district). The rural populations studied differ in the intensities and directions of gamete flows and their dynamics. There is no substantial gamete flow into the Ust-Aldan population from outside Sakha Republic. About 50% of marriages contracted in this population are homolocal (between residents of the same district); the endogamy is low (15%). In most cases of heterolocal marriages (contracted between residents of different districts), one of the spouses is a local resident. The inbreeding estimated from isonymy is FTT = 0.002930 in Yakuts; it is mainly accounted for by the nonrandom component (FIS = 0.002232 and FST = 0.000700).     

Ethnic marriage assortativeness and intensity of metisation of Karachays

On the basis of 11280 marriage records of four regions of Karachay-Cherkessia (Karachaevsky, Malokarachaevsky, Ust-Dzhegutinsky, Prikubansky, 193.2 thousand people in total) for 1990–2000, the intensity of Karachay cross-breeding was determined, amounting to 11.7%. Comparison of the intensity of Karachay cross-breeding with that for some other ethnoses is carried out. The ethnic assortativness H is approximately one. The population is characterized a preference for monoethnic marriages. The endogamy index in the studied regions varies from 0.29 to 0.53; after the exclusion from the analysis of repatriates, it increases to 0.34–0.63. The values of local inbreeding in an interval are 0.0001–0.0004, and no differences in terms of isolation by distance are revealed among the regions (0.001). The average square migration is 40–60 km.

     

Inbreeding and matrimonial structure in a Pyrenean community (Ansó, Huesca, Spain), 1712-1982

Using data from parish records from 1712 to 1982 in a Spanish Pyrenean village, Ansó, the effects of the raw nuptiality, the types of consanguineous marriages and the rate and evolution of inbreeding on the mating structure have been studied. This structure has been modified in the course of time mostly through the secular variations in the frequency of consanguineous marriages. Recent inbreeding decrease in Ansó is related to the population diminution and cultural changes associated with isolate breakdown.     

Population genetics of the population of the European north of the RSFSR. IV. The level of blood relationship in 5 villages of Pinega District, Archangel Province]

Computer program "RODAN-1" is used for inbreeding coefficient estimation. The population studied consists of two communities of 5 villages. 385 marriages were computed. The coefficient of inbreeding is 0.00145 for pedigree for rural Russian population (the Arkhangelsk region). The inverse dependence between a village size and corresponding data of inbreeding coefficient is suggested. An attempt was undertaken to estimate the genealogical information value for each pedigree and average information value for a village.     

Inbreeding and surnames: a projection into Easter Island's past

The population of Easter Island is one of the most interesting extant human communities due to its unique demographic history, its geographic isolation, and the development of an incomparable culture characterized by the towering "Moais" and its enigmatic writing. Following the colonization of its population by Polynesians from the Mangarevan Islands in the 5th century AD, the island remained isolated up until the middle of the 20th century. Under these conditions, with endogamy levels fluctuating between 61.04-96.54% and given such a small population, a high rate of inbreeding, and consequently, an elevated level of genetic relationships would be expected. Using data from church and civil records, we calculated the consanguinity of the population of Rapa Nui. The results of this analysis do not support the hypothesis of a high level of consanguinity (alpha = 0.00028 and F(t) = 0.0007, with F(r) = 0.00586 and F(n) = -0.00519), suggesting instead the existence of a strategy used to avoid marriage between close relatives. To explain these observations, the structure and exchange dynamics of the population were studied in the tribes, known locally as "Mata." The results of this analysis suggest a tendency toward the avoidance of inbreeding within tribes, in order to decrease the rate of endogamy in each group. This is consistent with ethnographic observations from the beginning of the 20th century that support the existence of strict regulations to prevent inbreeding between closely related individuals. Furthermore, we confirm that this situation dates back to a period before the "refounding" of Easter Island. Our results demonstrate that conditions of geographical isolation are not in themselves sufficient to produce an elevated inbreeding coefficient, revealing Easter Island as an interesting example of how cultural rules can shape the genetic structure of a population.     

Genetic Demographic Description of the Ust-Aldan Rural Population of Sakha Republic (Yakutia): Migrations and Marriage Structure

Migrations, dynamics of the gametic structure of rural populations, and marriage structure with respect to birthplaces and inbreeding estimated from isonymy have been studied in the Ust-Aldan ulus (administrative district) of Sakha Republic (Yakutia). The villages studied (Byadi, Dyupsya, and Cheriktey) are characterized by intense migration; however, the migration radius is small (most migrations occur within the district). The rural populations studied differ in the intensities and directions of gamete flows and their dynamics. There is no substantial gamete flow into the Ust-Aldan population from outside Sakha Republic. About 50% of marriages contracted in this population are homolocal (between residents of the same district); the endogamy is low (15%). In most cases of heterolocal marriages (contracted between residents of different districts), one of the spouses is a local resident. The inbreeding estimated from isonymy is F _IT = 0.002930 in Yakuts; it is mainly accounted for by the nonrandom component (F _IS = 0.002232 and F _ST = 0.000700).