Inbreeding in the Utah Mormons: an evaluation of estimates based on pedigrees, isonymy, and migration matrices

Using a computerized genealogical database, inbreeding coefficients were calculated for a sample of 435777 Utah Mormons. The population was divided into ten ten-year birth cohorts (1846–1945) and 22 geographic subdivisions in order to assess temporal and spatial variation in inbreeding. The average inbreeding coefficient for this population is 0.000 106. The average within-groups random kinship coefficient is 0.000 312, reflecting consanguinity avoidance. Random kinship matrices were formed by estimating the average kinship within each spatial subdivision and between all pairs of subdivisions. These matrices were compared statistically with kinship matrices previously estimated using migration matrices and isonymy data. The isonymy approach consistently overestimates random and total inbreeding as well as Wright's F_st. This can be attributed primarily to the assumption of monophyletic origin of surnames. The migration matrix method underestimates random inbreeding and F_st. This is due mainly to the assumption that outside immigrants are derived from a genetically homogeneous population. While the absolute values of the kinship coefficients estimated by each method differ substantially, the patterns of between-groups kinship coefficients given by each method are highly congruent. Logistic and linear regression analyses of 85 235 marriages demonstrate that consanguinity is significantly dependent upon year of marriage, geographic distance between husband's and wife's birthplaces, and the population size of husband's and wife's birthplaces.     

Family distances can reveal hidden consanguinity

Family distances, defined as summary measures of all possible geographic distances between birthplaces of paternal ancestors and birthplaces of maternal ancestors in a given generation, were compared in patients with autosomal recessive disorders and patients with Down's syndrome. In general, family distances in Down's syndrome patients were twice the family distances in patients with autosomal recessive disorders, even after the exclusion of rare disorders or cases with overt consanguinity. In modern, Western European societies grandparental and great-grandparental family distances may be more appropriate measures of the effect of population structure than parental distance or parental consanguinity.     

Consanguinity as risk factor for cervical carcinoma

Cervical carcinoma is caused by human papillomavirus (HPV). Among the risk factors for HPV infection are having multiple sex partners and sex partners who themselves had multiple sex partners. Women married to relatives are more likely to become infected with HPV and develop cervical carcinoma. Consanguineous spouses have a mild sexual aversion to each other that leads to sex avoidance and increases likelihood of satisfying sexual desire outside the marriage. Sexual aversion develops as a result of spouses growing together in early childhood, which triggers biological imprinting of Westermarck. Westermarck's effect prevents incest in nuclear family. In consanguineous family, it extends to spouses, producing mild sexual antipathy. Because of high prevalence of consanguinity worldwide, it is important to test this hypothesis.     

Population structure of two black Venezuelan populations studied through their mating structure and other related variables

In order to obtain information about the population structure of two black Venezuelan populations with historical differences both in their origins and development, a variety of variables were utilized, especially on marital structure, including: frequency of surnames, isonymy, population genealogical consanguinity, multiple unions, and marital distances, all of which provided information and isolation, migration, endogamy, consanguinity, and patri-matrifocality. Results showed differences in the extent of isolation and endogamy, as well as differences in population structure, which can be directly related with historical conditions of each population. Results agree with those previously obtained with traditional genetic polymorphisms and with the historical information available. Thus, the usefulness of surnames for inferring about population structure is supported, as well as the usefulness of historical information for explaining genetic diversity.     

Assortative mating,or who marries whom?

The first section reviews how much and what kind of assortative mating occurs. It considers the genetic consequences of any departure from random mating, then discusses the effects of consanguinity or inbreeding on the offspring. Suffice it to say here that these effects are generally unfavorable, so that one may say that forgenetic reasons a high similarity between spouses is not favored. The next section discusses the social consequences of marital choice in terms of theories and research related to mate selection and marital adjustment. At this point, we may summarize two opposing views of what makes for a good marriage: (1) psychological similarity and (2) complementariness of needs of husband and wife. We will see that most of the evidence tends to support the first view, so we can say that for social reasons similarity between spouses is favored. Another topic touched on is whether marriage leads to an increase in similarity over time, or, in genetic terms, to a partial convergence of phenotypes, which could lead to an overestimation of the degree of genotypic similarity. Next, the theory is discussed that homogamy for socioeconomic status is responsible for the observed correlations between abilities and between beauty and brains. The final section summarizes some research on factors influencing the personal preferences for personality and physical type which govern the selection of potential mates.Iwant a girl Just like the girl That married dear old dad (popular song of the 1920s)     

Population structure of the rural communities on the island of Krk (Croatia): A comparison of genetic,cultural, and geographic data

The population structure of seven rural communities from the island of Krk (Croatia) was studied on the basis of its genetic constitution and genetic structure, and different sets of biological (genetic), biocultural (migration), cultural (linguistic), and geographic data. Genetic constitution was estimated from the allelic frequencies of nine tetranucleotide STR loci, three HLA class I loci, five HLA class II loci, and five red blood cell enzyme and serum protein loci. Genetic structure was based on coefficients of genetic diversity G_ST and genetic kinship R_ST. Population structure was assessed by the structure of mutual relationships among biological, biocultural, cultural, and geographic matrices through Mantel's test, or by relationships among biological, biocultural, cultural measures of distance and/or similarity, and geographic distance with regression analysis of the “isolation by distance” model. One group of genetic markers (red blood enzymes, serum proteins, and HLA polymorphisms) reflects heterogeneity of the rural communities (a reflection of important historical processes and migration patterns), and a second group of genetic markers (STR polymorphisms) reflects the currently observed genetic homogeneity of the rural population. The positive correlations between the matrices of genetic (HLA) and linguistic distances indicate their possible co-evolution under conditions of genetic isolation (low gene flow). Furthermore, the negative correlations between the matrices of genetic (STR) distances and the migration kinship of the second and the third cohort indicate temporal coincidence between genetic constitution and structure assessed from STRs and migration patterns in the period between 1892 and 1940. Finally, the positive correlations between the matrices of genetic (STR) and geographic distances indicate isolation by distance. Am. J. Hum. Biol. 12:509–525, 2000. © 2000 Wiley-Liss, Inc.     

Estimation of inbreeding,kinship, genetic distances,and population structure from surnames: The island of Hvar,Croatia

The aim of this study was to estimate inbreeding, kinship, genetic distances, and population structure of the island of Hvar using surnames of the population from 10 villages. Total inbreeding on the island, estimated from the frequency of isonymous marriages, amounted to 0.0228. Total kinship (unreduced variance) of the entire island amounted to 0.0411, a value indicative of very isolated populations with accumulated kinship over time. The analysis of genetic relationships based on surnames among the villages did not reveal the division of the island's villages into two clusters, “eastern” and “western”, as was the case in previous studies when clustering was based on biological, biocultural, and sociocultural traits. In addition, kinship and genetic distances determined from surnames revealed a poor fit to an isolation by distance model (for kinship, R² = 14.6%, a = 0.1101, b = 0.3573; for genetic distances, R² = 0.0%, a = 0.5686, b = 121.52), which is in contrast to the results of previous analyses based on other traits. In order to estimate how closely parameters obtained from surnames represented real interpopulational distances, matrices of kinship and genetic distances between 10 villages (determined from surnames) were correlated to corresponding distance matrices based on migrational, sociocultural, anthropometric, physiological, dermatoglyphic, and genetic traits that were previously reported in the literature on the very same samples. The kinship matrix correlated poorly with other distance matrices, while the genetic distance matrix determined from surnames was in a good correlation with distance matrices based on linguistics (r = 0.65 for basic and r = 0.63 for cultural vocabulary), metacarpal bone dimensions (r = 0.54) and genetics (determined from systems of erythrocyte antigens and isoenzymes, r = 0.45). Am. J. Hum. Biol. 9:595–607, 1997. © 1997 Wiley-Liss, Inc.     

Spatial and temporal variation in kinship among Anopheles gambiae (Diptera: Culicidae) mosquitoes

Genetic relatedness (kinship) among Anopheles gambiae Giles female mosquitoes was assessed using microsatellite loci in five locations across Africa and in nine samples taken between 1994 and 1999 in western Kenya. We assessed variation among samples in kinship as well as the effect of distance on kinship. Relatedness within populations was low, and differences among samples taken at various times from one locale and from different locales were minimal. Mosquitoes collected from the same compound were slightly more closely related than those collected from different compounds. Our results suggest that newly emerged female siblings move relatively short distances into a few nearby compounds for blood feeding, but that they lay eggs in a more distant location. Kinship decreased nonlinearly with increasing distance. The strongest relationship between kinship and distance was observed for mosquitoes collected 0-3 km apart (-0.014/km, P < 0.001). The effect of distance decreased with increasing distance between mosquitoes; at 7 km or more, the kinship/distance slope approached zero and the intercept became negative, suggesting that beyond this range kinship does not decline with distance. This distance may thus represent the upper limit of the diameter of the basic reproductive unit. Nevertheless, the effect of distance on kinship is weak, reflecting extensive dispersal. Because females mate within days after emergence from larval habitats, where the likelihood of mating with a sibling is presumably highest, we propose a slight inbreeding effect.     

Modes of hantavirus transmission in a population of <Emphasis Type="Italic">Clethrionomys rufocanus bedfordiae</Emphasis> inferred from mitochondrial and microsatellite DNA analyses

Summary. To elucidate the mode of transmission of Puumala-related hantavirus in a population of gray red-backed voles, Clethrionomys rufocanus bedfordiae, in Hokkaido, Japan, we analyzed the kin structure and dispersal patterns of individual voles using microsatellite and mitochondrial DNA markers. Siblings or dam/offsprings was identified within the population based on the relatedness calculation with the microsatellite data. The pairwise relatedness values obtained could reveal kinship among all vole individuals within the population. Based on the assessment of kinship, we did not find a positive relationship between hantavirus transmission and close kinship. Males infected with the hantavirus carried a relatively uncommon mitochondrial haplotype. However, these infected males shared low relatedness values and were not considered closely related, i.e., they were not siblings or parent/offspring. These observations imply that hantavirus transmission in the vole population may not be related to close kinship but by random horizontal infection.     

Kinship by isonymy and by gene frequencies: A comparison of population structures at different hierarchical population levels

A comparison of population structures based on isonymy and on gene frequencies (ABO, Rh, Kell) was conducted for a sample of 28,205 individuals residing in three different provinces (Lucca, Massa Carrara, La Spezia) in northwest Italy, on the basis of both chronological and spatial subgroupings. Relationships between and within population subsamples were measured by means of kinship coefficients. The aim of this study was focused on kinship decay with geographic distance, associated with the great difference in location and variability between isonymic and genetic data. The analysis was carried out by R_st statistics and regression analysis to test the fit of the isolation by distance models. Further, the R matrices were converted into a distance measure, and Mantel's permutation test was used to assess the correlation across isonymy, genetic, and geographic matrices. Whereas estimates of R_st and isolation by distance parameters obtained from genetic and surname data pointed to a roughly comparable basic pattern of spatial differentiation in both chronological periods, the absolute values differ substantially. Both R_st and a isolation by distance parameters estimated from genetic data were higher than those from surnames, indicating greater local isolation by genetic analysis. The standard errors of b obtained from surname data were much smaller than those computed from genetic data, indicating that the kinship by isonymy coefficients fit Malècot's model better than the kinship coefficients estimated by the genetic data. Squared correlation coefficients among geographic, surname, and genetic distance matrices supported the above interpretations. The strong localization of surnames, the different level of variability in surname and gene frequency data, and random variations (due to the number of alleles considered) seem to be the main reasons for the observed differences between the two data sets. © 1996 Wiley-Liss, Inc.     

Isonymic analysis of post-famine relationships in the Ards Peninsula,N.E. Ireland: Effects of geographical and politico-religious boundaries

During and in the decades after the Irish Famine of 1846 to 1851, the population of the Ards Peninsula, Co. Down, both declined in numbers and changed in its composition. In 1863 the surnames of all resident householders were collected as part of a national valuation. These data have been used to calculate random isonymy values between civil parishes and the resultant matrix plotted by nonmetric multidimensional scaling. The results revealed both a major geographical barrier to gene flow, and politico-religious boundaries in existence since the early 17th century. The inter-relationships between random isonymy, geographical distance, and religious denominational frequencies within the peninsula were investigated by multiple regression analysis. While geographical influences predominated over short and long distances, in the intermediate distance range religion played the dominant role. The net effect of these subdivisions, in combination with famine-associated population losses, would have been to reduce local effective population sizes significantly, thus enhancing the potential for genetic drift and random inbreeding.     

Genome-wide patterns of identity-by-descent sharing in the French Canadian founder population

In genetics the ability to accurately describe the familial relationships among a group of individuals can be very useful. Recent statistical tools succeeded in assessing the degree of relatedness up to 6–7 generations with good power using dense genome-wide single-nucleotide polymorphism data to estimate the extent of identity-by-descent (IBD) sharing. It is therefore important to describe genome-wide patterns of IBD sharing for more remote and complex relatedness between individuals, such as that observed in a founder population like Quebec, Canada. Taking advantage of the extended genealogical records of the French Canadian founder population, we first compared different tools to identify regions of IBD in order to best describe genome-wide IBD sharing and its correlation with genealogical characteristics. Results showed that the extent of IBD sharing identified with FastIBD correlates best with relatedness measured using genealogical data. Total length of IBD sharing explained 85% of the genealogical kinship''s variance. In addition, we observed significantly higher sharing in pairs of individuals with at least one inbred ancestor compared with those without any. Furthermore, patterns of IBD sharing and average sharing were different across regional populations, consistent with the settlement history of Quebec. Our results suggest that, as expected, the complex relatedness present in founder populations is reflected in patterns of IBD sharing. Using these patterns, it is thus possible to gain insight on the types of distant relationships in a sample from a founder population like Quebec.     

Persistent genetic isolation in outport Newfoundland

The historical development of genetic isolation has been evaluated for three outport Newfoundland study areas. An attempt was made to ascertain all livebirths in each study area, and determine the parentage of each. Data from records of baptism and marriage were used for this, supplemented with other historical and ethnographic information. Parent-offspring migration was used as a measure of genetic exchange between subpopulations within study areas, and gene flow into the study areas. Currently, 1-8% of parents originate outside the study areas; these rates are low compared to earlier periods, and compared to present-day rates for European isolate populations. Average kinship was estimated, to measure genetic relatedness within and between subpopulations of each area and the potential for random inbreeding; these values, which are minimum estimates, are now at historically high levels. Increased migration into the study areas, which would decrease average kinship, is not likely. Thus, any regionally or locally elevated frequencies of deleterious alleles will persist, and must be taken into account in providing genetic counseling and evaluating the utility of local screening programs.     

Genetic structure of the Utah Mormons: A comparison of kinship estimates from DNA blood groups,genealogies, and ancestral arrays

Kinship estimates based on shared proportions of European ancestry are constructed for 284 Utah males born in eight geographic subdivisions. These “ancestral kinship” estimates are compared with kinship coefficients based on DNA polymorphisms, blood groups, genealogies, isonymy, and migration matrices. At the subdivision level, a high correlation is observed between ancestral kinship and kinship based on isonymy. Comparing individuals, a significant correlation is obtained between ancestral kinship and genealogy derived kinship. Kinship estimates based on DNA and blood groups do not correlate significantly with ancestral kinship. This is most likely due to the effects of several generations of random mating in this population. © 1996 Wiley-Liss, Inc.     

Deep genealogical analysis of a large cohort of participants in the CARTaGENE project (Quebec,Canada)

Background: Genealogical analysis helps to better understand the genetic structure of populations. The population of Quebec (Canada) often serves as a model for this type of analysis, having one of the world’s most complete genealogical databases.

Aim: The main objective of this study was to reconstruct, analyse and compare the ascending genealogies of participants to CARTaGENE, a project that aims at building a database on various aspects of public health.

Subjects and methods: In total, 5110 genealogies from four Quebec regions were reconstructed. Distribution of ancestors, completeness and depth of the genealogies, characteristics of immigrant ancestors and kinship and inbreeding coefficients were analysed.

Results: Most genealogies go back to the 17th century, with a mean genealogical depth of 10 generations. Origins of immigrant ancestors are more diverse in the Montreal region, resulting in lower inbreeding and kinship among the participants from this region. Inbreeding and kinship values are mainly explained by remote genealogical links (from 6 to 11 generations).

Conclusion: Deep genealogies allowed for a precise measurement of the geographic origins of the participants’ immigrant ancestors, as well as inbreeding and kinship ties in the population, which may be crucial for studies aiming to identify genetic variations associated with Mendelian or complex diseases.     

Inbreeding effects on human reproduction in Tamil Nadu of South India

A prospective investigation of inbreeding effects was carried out during 1969-74 on representative samples from rural and urban populations of Tamil Nadu in southern India. Altogether, 14243 pregnancy terminations were observed. Forty-seven per cent of the rural women and 29% of urban were consanguineously married; in 80% or more of these marriages the spouses were first cousins or more closely related. The differences between the consanguineous and non-consanguineous marriages were studied with respect to total foetal loss rates, neonatal, infant and perinatal and extended first-year mortality rates; in these cases the differences were quite small and unlikely to have practical importance, though some attained statistical significance. Differences for duration-specific foetal loss, sex ratio and incidence of congenital malformations were not statistically significant. When studied alternatively in terms of the regression of the incidence rate on the inbreeding coefficient, again most regression coefficients were mostly positive but did not reach the 0.05 significance level. Taking into account the background of the population studied, the methodology adopted, and the lack of significant patterns by type of parental consanguinity, the most reasonable conclusion is that the continued practices of consanguinity over several generations have narrowed the differentials of human reproduction and of its wastage among various types of marriages based on parental consanguinity.     

An insight into recent consanguinity within the Basque area in Spain. Effects of autochthony, industrialization and demographic changes

BACKGROUND: The importance of studying the genetic kinship of those human groups characterized by a deeply rooted ethnicity has traditionally been and still is an interesting goal of anthropological and population genetic studies. However, only a few surveys have aimed to learn about the impact of industrial development on the consanguinity of these populations and even those have concentrated on industrialized regions. This approach is worth analysing in Spain, where industrialization was late in relation to other western European countries. AIM: In this work we analyse the characteristics of inbreeding in Guipúzcoa from 1951 to 1995. This Basque province underwent industrial and tourist development earlier than other Spanish regions. It has the highest density of Basque speakers and has always occupied a central position within the map of distribution of the Basque language. Guipúzcoa is geographically placed in the core of the Basque area. SUDJECTS AND METHODS: Data on consanguineous marriages recorded in the province of Guipúzcoa between 1951 and 1995 were taken from Roman Catholic dispensations stored in the Diocesan Archives of San Sebastián, the province's capital city. Over the whole time period, a total of 1152 consanguineous marriages were registered. RESULTS: The high frequencies of first cousin (M22) (F = 1/16) and uncle-niece, aunt-nephew (M12) (F = 1/8) consanguineous marriages distinguish Guipúzcoa from the rest of Iberian populations. The M22/M33 ratio (with M33 being second cousins) has never dropped below 0.67, which represents a significant deviation from the expectation value of 0.25. When consanguineous marriages are classified according to marriage partner birthplaces interesting results emerge. Provincial endogamy shows the highest consanguinity rates (57%) and the proportion of M22/M33 is also rather high (0.63). However, a major contribution to the consanguinity levels and mean inbreeding coefficient recorded in Guipúzcoa over recent decades has been made by immigrant relative groups coming from other geographical areas of Spain. In this segment of population the observed M22/M33 rates are 1.44. CONCLUSIONS: This study shows again how important preferentiality (or avoidance) is in human consanguinity, and also how human groups, in spite of being spatially settled in the same territory, present differential attitudes for given consanguinity patterns.     

Genome-wide inbreeding estimation within Lebanese communities using SNP arrays

Consanguineous marriages have been widely practiced in several global communities with varying rates depending on religion, culture, and geography. In consanguineous marriages, parents pass to their children autozygous segments known as homozygous by descent segments. In this study, single-nucleotide polymorphisms were analyzed in 165 unrelated Lebanese people from Greek Orthodox, Maronite, Shiite and Sunni communities. Runs of homozygosity, total inbreeding levels, remote consanguinity, and population admixture and structure were estimated. The inbreeding coefficient value was estimated to be 1.61% in offspring of unrelated parents over three generations and 8.33% in offspring of first cousins. From these values, remote consanguinity values, resulting from genetic drift or recurrent consanguineous unions, were estimated in offspring of unrelated and first-cousin parents to be 0.61 and 1.2%, respectively. This remote consanguinity value suggests that for any unrelated marriages in Lebanon, the mates could be related as third cousins or as second cousins once removed. Under the assumption that 25% of marriages occur between first cousins, the mean inbreeding value of 2.3% may explain the increased incidence of recessive disease in offspring. Our analysis reveals a common ancestral population in the four Lebanese communities we studied.     

Mating structure, isonymy and social class in late nineteenth century Tasmania

This study analysed all marriages (N = 4258) registered in the island State of Tasmania during the period 1896-1899 for mating structure, using marital isonymy. We found that irrespective of the geographic size of the subdivisions the random component (Fr) values were similar. This is because there was a high proportion of unique names despite the large population size. Fn values were sensitive to geographic distance only with respect to the 'unrealistically' larger units of analysis. Isonymy is valid over very large distances in Tasmania. Inbreeding values in the study were typical of other mainstream populations, but the nonrandom component was unusually high. Farmer marriages were the major contributors to the high Fn values. One particular region, the Midlands, displayed both a high F (0.0081) and Fn (0.0074) component. The explanation of these values lies in the effects of a rigid socio-economic structure established during colonization.     

Marital migration and genetic structure in Kitee, Finland

A genetic analysis of marital migration in Kitee, Finland, is presented. The data are based on 9970 marriages which took place between 1750 and 1877. The results of this analysis are compared with those of previous studies of the population of the Aland Islands, Finland. Analysis of inter-subdivision genetic kinship matrices shows that genetic heterogeneity in Kitee is substantially less than in Aland. This is due primarily to higher rates of migration, both between subdivisions and from outside the population, in Kitee compared to Aland. These differences in migration rates can in turn be attributed to greater geographic isolation in Aland and the contrasting social structures of the two populations. Because of differences in geographic structure and population distribution, geographic distance between subdivisions is a better predictor of inter-subdivision genetic kinship in Kitee than in Aland. The Aland Islands are known to have high frequencies of several otherwise rare genetic diseases; in addition, these diseases are distributed very non-randomly among Aland's subdivisions. The genetic structure results presented here suggest that Kitee should have a less unique distribution of genetic diseases.