Consanguineous marriages in Afghanistan

The present cross-sectional study was done in order to illustrate the prevalence and types of consanguineous marriages among Afghanistan populations. Data on types of marriages were collected using a simple questionnaire. The total number of couples in the study was 7140 from the following provinces: Badakhshan, Baghlan, Balkh, Bamyan, Kabul, Kunduz, Samangan and Takhar. Consanguineous marriages were classified by the degree of relationship between couples: double first cousins, first cousins, first cousins once removed, second cousins and beyond second cousins. The coefficient of inbreeding (F) was calculated for each couple and the mean coefficient of inbreeding (α) estimated for each population. The proportion of consanguineous marriages in the country was 46.2%, ranging from 38.2% in Kabul province to 51.2% in Bamyan province. The equivalent mean inbreeding coefficient (α) was 0.0277, and ranged from 0.0221 to 0.0293 in these two regions. There were significant differences between provinces for frequencies of different types of marriages (p<0.001). First cousin marriages (27.8%) were the most common type of consanguineous marriages, followed by double first cousin (6.9%), second cousin (5.8%), beyond second cousin (3.9%) and first cousin once removed (1.8%). There were significant differences between ethnic groups for the types of marriages (χ2=177.6, df=25, p<0.001). Tajiks (Soni) and Turkmens (also Pashtuns) showed the lowest (α=0.0250) and highest (α=0.0297) mean inbreeding coefficients, respectively, among the ethnic groups in Afghanistan. The study shows that Afghanistan's populations, like other Islamic populations, have a high level of consanguinity.     

Consanguineous marriage among the Fulani

The Fulani are a broad ethnic category of nomadic and seminomadic pastoralists and agropastoralists living in the semiarid Sahel region of sub-Saharan Africa. The Fulani are patrilineal, patrilocal, and moderately polygynous, with arranged first marriages accompanied by the payment of bridewealth, ideally in the form of cattle. Consanguineous marriage is frequent, with first or second cousin marriage preferred. In this paper we present data on levels of consanguineous marriage among the Fulani of northern Burkina Faso and test the hypothesis that inbreeding may be more frequent when there is a scarcity of cattle available, since bridewealth demands are thought to be reduced with close-kin marriage. Among 308 women's marriages, 203 (65.8%) were between kin up to and including second cousins, and 102 (33.1%) were between nonkin. Among 276 men's marriages, 196 (71.0%) were between kin up to and including second cousins, and 77 (27.9%) were between nonkin. The mean population inbreeding coefficient (alpha) was 0.0355 for women, and 0.0374 for men. No increase was found in population levels of inbreeding estimated from marriages contracted after the droughts of 1973 and 1984, which drastically reduced the Fulani's cattle stocks. However, a significantly higher rate of consanguineous marriage was found in families owning the fewest cattle.     

Inbreeding avoidance behaviors

Inbreeding is defined as mating between individuals related by common ancestry. Thus, the degree to which a particular mating is inbred depends on how far back in a pedigree one begins counting common ancestors. In general practice, the term inbreeding is used to describe mating between close relatives (first cousins or closer). Animal breeders have known for centuries that inbreeding causes a loss of constitutional vigor and fertility in domestic livestock. A growing literature now demonstrates that the offspring of matings between close relatives in species of undomesticated birds and mammals are less fit than outbred offspring. The deleterious consequences of inbreeding suggest the possibility that many species have evolved behaviors that lower the frequency of inbreeding.     

Estimates of cousin marriage and mean inbreeding in the United Kingdom from 'birth briefs'

From 626 ascendant genealogies, known as 'birth briefs', deposited by members of the Society of Genealogists in their London library, rates of consanguineous marriage and coefficients of mean inbreeding (a) of offspring were estimated for cohorts of marriages contracted in the late nineteenth and early twentieth centuries. The rate of first cousin marriage in the generation estimated to have married during the 1920s was 0.32%, with no marriages between second cousins. The mean inbreeding coefficient for the offspring of these marriages was estimated as 0.0002. In the previous generation 1.12% of the marriages were between first cousins, and the estimate of mean inbreeding was 0.0007. Comparison with data taken from the published literature suggests that the levels of cousin marriage observed are consistent with a secular decline during the late nineteenth and twentieth centuries.     

Consanguineous marriage in a newly developed country: the Qatari population

This study examines the frequency of consanguineous marriage and coefficient of inbreeding in the State of Qatar. The study was conducted in semi-urban areas of Doha between January and May 2004. A sample of 1515 married Qatari females aged 15 years and over participated. The degree of consanguinity between each female and her spouse, and degree of consanguinity between their parents were recorded. The rate of consanguinity in the present generation was high (54.0%) with a coefficient of inbreeding of 0.02706. The commonest type of consanguineous marriage was between first cousins (34.8%). Double first cousin marriages were common (3.1%) compared with other populations. The consanguinity rate in the State of Qatar has increased from 41.8% to 54.5% in one generation.     

An estimation of inbreeding from isonymy in the historical (1734-1810) population of the Quebrada de Humahuaca (Jujuy, Argentina)

The method of isonymy to estimate inbreeding is applied to the historical population of the Quebrada de Humahuaca (Province de Jujuy, Republic of Argentina). Data from the baptismal records of the Parochial Church of Humahuaca from 1734 to 1810 were grouped into two periods, 1734-72 and 1773-1810. The analysis was carried out twice: (a) using the surnames exactly as they were registered; (b) combining homonymous surnames which were pronounced or spelt in a similar way. The random and non-random components of inbreeding have been investigated through different methods. There were no significant differences between the results of the two analyses, nor between the expected and observed isonymy. The value of F lies somewhere between those for offspring of first cousins once removed and second cousins once removed. There is a tendency for F and its components to increase through time. It is concluded that the high altitude aboriginal population of Humahuaca Parish must have behaved as a panmictic unit.     

Age-specific differences in blood pressure among inbred and non-inbred north Indian children

Genetic and inbreeding influences on systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial blood pressure (MBP) were examined among 3015 children (1527 males and 1488 females) from the Aligarh district, Uttar Pradesh in north India. The subjects included offspring of first cousins, first cousins once removed, second cousins and unrelated spouses from the same population. The measurements of the inbred children were compared with those of their non-inbred relatives in at least 80% of the cases (matched controls). Two unique findings emerge from this study. First a consistent increase in mean values of SBP, DBP and MBP with increasing inbreeding coefficients have been observed among all age groups, including both the sexes. The results suggest that the hypothesis for a recessive gene or genes could be held responsible for higher BP. Secondly, the effects of inbreeding on mean blood pressure among children and adults may not necessarily be in the same direction. It can be said, therefore, that studies on inbreeding effects using matched controls may provide more direct information regarding the genetics of blood pressure, which has been considerably underestimated in earlier studies.     

Inbreeding effects on metrical phenotypes among North Indian Children

This study aimed to examine the effects of inbreeding on 12 quantitative phenotypes like body weight, height, sitting height, head circumference, head length, head breadth, chest circumference, verbal, performance and full scale intelligence quotients, systolic and diastolic blood pressures among North Indian Children. The sample consisted of 3,253 subjects (1,683 males and 1,570 females) including offspring of first cousins, first cousins once removed, second cousins, (inbred part of samples) and unrelated spouses (non-inbred part of samples) ranging in age from 6 to 14 years from the Aligarh district, Uttar Pradesh in North India. Samples were selected purposively to estimate the average inbreeding coefficients based on 3 ancestral generations and using Wright's path method. The average inbreeding coefficient of the present inbred part of sample is 0.04609. The mean ages of males and females were almost equal for both inbred and non-inbred individuals. A significant reduction of means (p < 0.05) or inbreeding depression has been observed in inbred series for all anthropometric and psychometric traits for both the sexes. A significant elevation of mean with inbreeding is observed for systolic and diastolic blood pressure. The average inbreeding depression per 10% inbreeding appeared very high in verbal IQ (> or =23), performance IQ (> or =40), full scale IQ (> or =28), systolic blood pressure (> or =10) and diastolic blood pressure (> or =12) among both sexes. On the whole, relatively greater amount of inbreeding effects are apparent among all measures of intelligence quotient and blood pressures compared to the anthropometric traits. The results of the present work have thrown light on the nature and mechanism of genetic effects of inbreeding on certain quantitative traits in human.     

Consanguineous marriages in the population of Sheikhupura (Punjab), Pakistan

This study was based on 1007 couples from the Sheikhupura population. The proportions of various parental relationships were: 0.3784 1st cousins, 0.0318 1st cousins once removed, 0.0784 double 2nd cousins, 0.1033 bradari distant relations, 0.3416 bradari, and 0.0665 unrelated parents. Mean paternal ages in unrelated couples are significantly higher than in 1st cousins, double 2nd cousins, and bradari relations. The differences in paternal and maternal ages are significantly higher in unrelated relations as compared to 1st cousins and double 2nd cousins. Procounced effects of consanguinity on parental deaths and neonatal deaths were observed in 1st cousin marriages compared to other relationships. Juvenile and infant deaths show comparatively less effects of consanguinity in 1st cousin marriages. Mean coefficient of inbreeding calculated for this population was 0.0271. Lethal gene equivalents calculated were 1.5424. The added risk of affected children in 1st cousins over that of unrelated parents was 4.82%. The results suggest that the deleterious genes show their effects more in the prenatal than in the postnatal period.     

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.     

Estimation of inbreeding by isonymy in Iberoamerican populations: an extension of the method of Crow and Mange

The method of isonymy for the estimation of inbreeding levels was extended to use the potentialities offered by the Iberoamerican surname system, in which a child inherits his surnames both from the father and the mother. Four possible types of isonymy were recognized between the family names of a husband-wife pair. It was found that, limited to simple consanguinity, the ratio between isonymy and the inbreeding coefficient of consanguineous individuals, starting from first cousins, is constant and equal to 16. Consanguinity levels were studied in four Venezuelan groups, Isla de Toas, Los Teques, Quibor, and Colonia Tovar, using genealogies, classical isonymy, and the extended method. It was found that, for Iberoamerican populations, the extended method is more precise than the classical method.     

Inbreeding effects on reproductive outcome in a Sudanese population

926 women attending the Obstetrics and Gynaecology Department of the Faculty of Medicine, Khartoum, were investigated to study the inbreeding effects on reproductive profiles and morbidity of the offspring. 49.5% of the women had married their first cousins and 13.8% had married more distant relatives. Altogether, 4,471 pregnancy outcomes were analysed including abortions, still births, neonatal and childhood deaths, physical deformity, mental retardation and other congenital abnormalities. No significant difference in the reproductive loss or net fertility was observed between the inbred and outbred groups. Only the proportions of childhood deaths were found to be significantly higher in the inbred marriages (p less than 0.005). The morbidity was also not affected by the practice of inbreeding.     

Preference for Outbreeding in Inbred Littledale’s Whistling Rats <Emphasis Type="Italic">Parotomys littledalei</Emphasis>

Inbreeding is sometimes tolerated in species occupying patchy, unpredictable habitats, when it becomes too costly to outbreed. Although traits leading to inbreeding depression may be selected against, the accumulation of deleterious alleles from constant inbreeding might promote outbreeding. Littledale’s whistling rat Parotomys littledalei occupies patchy habitats in arid western South Africa, and inbreeds in captivity without suffering inbreeding depression. We tested whether female whistling rats make different mate choice decisions based on their inbreeding status, by providing inbred and outbred females with male odours in four pairwise combinations: unrelated outbred (r = 0) versus either familiar littermate sibling (r = 0.5), half-sibling (r = 0.25), first cousin (r = 0.125), or unrelated inbred (r = 0). Inbred females generally preferred unrelated males, but did not show a preference between unrelated males and first cousins. In contrast, outbred females did not generally show a preference, but preferred first cousins to unrelated males. In breeding trials, reproductive success (output and viability of young) of outbred females paired with unrelated or related males was equally high, whereas inbred females suffered reduced reproductive success when paired with closely-related males. Our results indicate that the inbreeding status of female whistling rats influences their decision to outbreed or inbreed, which might influence their fitness. While outbred whistling rats do not suffer inbreeding depression, the costs of constant inbreeding could promote outbreeding by inbred females. We propose that the choice to inbreed or outbreed in female whistling rats depends on their inbreeding status and the genetic relatedness of available mates, with outbreeding more likely to occur unless unrelated mates are not available.     

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

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.     

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     

A neurogenetic study in an inbred population]

A Tatar family from a semi-isolated village in the Gorky Region is described in which a neurological and ophthalmological syndrome was inherited. In homozygotes this syndrome comprised the degeneration of subcortical cerebral ganglia (hyperkinesis), nystagmus, oligophrenia and a peculiar variant of tapetoretinal degeneration. Heterozygotes exhibited ophthalmological abnormalities, such as the similar defects of eye bottom and nystagmus. The two homozygotes observed were sibs derived from a marriage between first cousins. Five more families with other rare hereditary anomalies (both dominant and recessive) were discovered in this village. The total inbreeding coefficient in the village was found to be 0.0075. The high degree of inbreeding, subisolation and high fertility are regarded as factors favorable for the distribution of rare deleterious mutations due to the founder-effect.     

Inbreeding depression in a critically endangered carnivore

Harmful effects arising from matings between relatives (inbreeding) is a long‐standing observation that is well founded in theory. Empirical evidence for inbreeding depression in natural populations is however rare because of the challenges of assembling pedigrees supplemented with fitness traits. We examined the occurrence of inbreeding and subsequent inbreeding depression using a unique data set containing a genetically verified pedigree with individual fitness traits for a critically endangered arctic fox (Vulpes lagopus) population. The study covered nine years and was comprised of 33 litters with a total of 205 individuals. We recorded that the present population was founded by only five individuals. Over the study period, the population exhibited a tenfold increase in average inbreeding coefficient with a final level corresponding to half‐sib matings. Inbreeding mainly occurred between cousins, but we also observed two cases of full‐sib matings. The pedigree data demonstrated clear evidence of inbreeding depression on traditional fitness traits where inbred individuals displayed reduced survival and reproduction. Fitness traits were however differently affected by the fluctuating resource abundande. Inbred individuals born at low‐quality years displayed reduced first‐year survival, while inbred individuals born at high‐quality years were less likely to reproduce. The documentation of inbreeding depression in fundamental fitness traits suggests that inbreeding depression can limit population recovery. Introducing new genetic material to promote a genetic rescue effect may thus be necessary for population long‐term persistence.     

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.     

Consanguineous marriage in the capital city Sana'a, Yemen

Consanguineous marriage is traditionally common throughout the Eastern Mediterranean region, especially in the mainly Muslim countries. To date, there is little information on consanguinity in Yemen. The aim of this study was to ascertain the rate of consanguineous marriage and average coefficient of inbreeding in Sana'a City, Yemen. A population survey was conducted with the intention of covering married couples resident in Sana'a City by means of a multi-stage random sampling technique. A total of 1050 wives and husbands were interviewed on consanguinity in their households. The total incidence of consanguinity was 44-7% (95% CI 41.7-47.7%) with first-cousin marriages constituting 71.6% of the total consanguineous marriages and 32% of all marriages. Paternal parallel first cousins (Type I) accounted for 49% of first-cousin marriages. The average coefficient of inbreeding (F) was 0.02442. The incidence of consanguinity is relatively high in Yemen with predominantly first-cousin marriage. This might be related to the deeply rooted social and cultural beliefs in the country.