Paquimé (also known as Casas Grandes), situated in northern Chihuahua between Mesoamerican and Ancestral Puebloan groups, was a vibrant multicultural centre during the thirteenth and fourteenth centuries AD. Substantial debate surrounds the social organisation of Paquimé's inhabitants. Here, the authors report on the analysis of ancient DNA from a unique child burial beneath a central support post of a room in the House of the Well. They argue that the close genetic relationship of the child's parents, revealed through this analysis, and the special depositional context of the burial reflect one family's attempts to consolidate and legitimise their social standing in this ancient community.

The aim of this study was to determine the trend of consanguineous marriage among the Arab population in Israel. Socio-demographic data for the Arab population were extracted from national health surveys conducted in Israel in 2007 and 2017. The prevalence of consanguineous marriage among the Arab population in Israel increased significantly from 36.3% to 41.6% in the decade from 2007 to 2017. First-cousin and closer marriages constituted about 50% of total consanguineous marriages in the two periods surveyed. Consanguinity was found to be significantly related to religion and place of residence. Thus, the prevalence of consanguineous marriage remains high among the Arab population in Israel, similar to other Arab societies. These findings affect the health of future generations and impose a challenge for health care professionals.

Consanguineous marriage is a deeply rooted tradition in the Arab world. Such marriages are linked to higher rates of recessive genetic diseases. During the Syrian conflict, which started in 2011, around one million Syrian individuals became refugees in Lebanon. This study assessed the consanguinity rates among Syrian refugees living in Lebanon up to three successive consanguineous generations, and examined refugees’ awareness of the possible consequences of consanguineous marriage and their attitudes towards consanguinity. Their knowledge of, and access to, premarital screening was also assessed. The study was conducted between January and May 2018. Several study sites representing refugees’ distribution within the country were chosen. The study sample included 1008 interviewees from different families. Of those interviewed, 51.9% were in a consanguineous marriage. Interestingly, 23.9% were the product of consanguineous marriages themselves, and 17.9% were consanguineous for three successive generations. The interviewees generally knew about premarital screening, but the majority (61.9%) had not had the screening. The high rates of consanguinity in these Syrian refugees call for immediate action, including raising genetic awareness and providing appropriate genetic counselling. Despite the respondents’ familiarity with premarital screening, there was a low rate of uptake of the test, underscoring the importance of providing better education to these refugees.

Several studies have affirmed the existence of a strong and complex genetic component in the determination of psychotic disorders. However, the genetic architecture of these disorders remains poorly understood. GWAS studies conducted over the past decade have identified some associations to low effect, and the major part of this heritability remains unexplained, thus calling into question the hypothesis of “common disease – common variant” for model involving a large number of rare variants. Family studies of extended pedigrees selected from geographical isolate can be a powerful approach in identifying rare genetic variants of complex diseases such as psychotic disorders. Here, we studied four multigenerational families in which co-exist psychotic and mood disorders and a high rate of consanguinity, identified in the northwest of Algeria. This case-control study aimed to characterize new rare genetic variants responsible for psychosis. These families have received complete clinical and genealogical investigations, genome wide analysis that were performed in the laboratory of medical genetics in the university hospital of Geneva. A genome wide research CNVs using Agilent Human Genome CGH Microarray Kit 44 K, covering 45 subjects including 20 patients and in a control population of 55 individuals. Three CNVs that had never been reported to date have been identified in one of four families and validated by two techniques. It is the dup 4q26, and 16q23.1 del del21q21. These CNVs are transmitted by either parent line, suggesting a cumulative effect on the risk of psychotic disorders. Further analyzes using pan-genomic linkage analysis using GWAS chip (Illumina Human 660 W-Quad v1.0 Breadchip) and complete WES (by GAIIx Illumina/HiSeq 2000) were performed in some related individuals to search other mutations may explain the appearance of the phenotype in this population.

Consanguinity is usually defined as the result of a sexual reproduction between two related individuals. It can also refer to populations sharing at least one common ancestor, as those who live within isolates or within communities practicing endogamy. Second or higher order related couples and their offspring represent more than 10% of the current world population. The highest levels of consanguinity are found in the Southern and Eastern shores of the Mediterranean Basin, and the most concerned region extends from the southern shore of the Mediterranean Sea to Southeast Asia through Middle-East, Gulf and India. In Maghreb countries, consanguineous marriages are wide-spread. The rates for this practice vary from 23% in Morocco to 60% in Tunisia, with highest rates being found in rural areas. In Algeria, consanguineous marriages represent more than 38% of all marriages. Large scale migrations from South countries to North countries in the second half of the twentieth century had legal impact on migrants for these specific unions. As a consequence, controversies have been rising in the United States and the United Kingdom especially when a fast decrease of inter-related individuals unions seems unlikely. Consanguinity certainly increases the risk of autosomal recessive pathology, but what about mental pathologies with complex and polygenic heredity? The necessity of an awareness of the genetic risks of consanguinity is as essential in countries where inter-cousin unions are culturally encouraged as among migrant populations in Europe.

To an extent the question posed in the title of this paper can simply be answered in the affirmative. Based on the extensive data available from the National Family Health Survey-1 (NFHS-1) conducted in 1992–93 and NFHS-4 in 2015–16 there has been a significant overall decline of some 19% in the prevalence of consanguineous marriage in India. However, when examined at state level the picture is more complex, with large reductions in consanguinity in southern states where intra-familial marriage previously has been strongly favoured, whereas in some northern states in which close kin unions traditionally have been proscribed small increases were recorded. In a country such as India, comprising an estimated 18% of the current world population and with multiple ethnic, religious, geographical and social sub-divisions, apparently contrary findings of this nature are not unexpected – especially given the major shifts that are underway in family sizes, in education and employment, and with rapid urbanization. The changing health profile of the population also is an important factor, with non-communicable diseases now responsible for a majority of morbidity and premature mortality in adulthood. The degree to which future alterations in the prevalence and profile of consanguineous marriage occur, and at what rate, is difficult to predict – the more so given the markedly diverse cultural identities that remain extant across the Sub-Continent, and ongoing intra-community endogamy.

Consanguineous marriages potentially play an important role in the transmission of β-thalassaemia in many communities. This study aimed to determine the rate and socio-demographic associations of consanguineous marriages and to assess the influence on the prevalence of β-thalassaemia in Sri Lanka. Three marriage registrars from each district of Sri Lanka were randomly selected to prospectively collect data on all couples who registered their marriage during a 6-month period starting 1st July 2009. Separately, the parents of patients with β-thalassaemia were interviewed to identify consanguinity. A total of 5255 marriages were recorded from 22 districts. The average age at marriage was 27.3 (±6.1) years for males and 24.1 (±5.7) years for females. A majority (71%) of marriages were ‘love’ marriages, except in the Moor community where 84% were ‘arranged’ marriages. Overall, the national consanguinity rate was 7.4%. It was significantly higher among ethnic Tamils (22.4%) compared with Sinhalese (3.8%) and Moors (3.2%) (p < 0.001). Consanguinity rates were also higher in ‘arranged’ as opposed to ‘love’ marriages (11.7% vs 5.6%, p < 0.001). In patients with β-thalassaemia, the overall consanguinity rate was 14.5%; it was highest among Tamils (44%) and lowest among Sinhalese (12%). Parental consanguinity among patients with β-thalassaemia was double the national average. Although consanguinity is not the major factor in the transmission of the disease in the country, emphasis should be given to this significant practice when conducting β-thalassaemia prevention and awareness campaigns, especially in high-prevalence communities.

The aim of this cross-sectional study was to investigate beliefs, attitudes and reproductive behaviours in relation to consanguinity in a population living in the backlands of north-eastern Brazil. Data were collected by face-to-face interview from 147 high school students aged 13–20 years and from 532 elderly individuals aged 60 years and over from Brejo dos Santos in the state of Paraíba in 2017. The frequency of consanguineous marriage was found to have increased over the generations, being 15.9% in the parents of the elderly participants, 17.1% in the elderly participants themselves and 20.5% in their descendants. Although 258 (50.9%) of the elderly interviewees opposed consanguineous union, 341 (65.3%) would approve of the marriage of their children with relatives. Both the young (n=108 or 78.3%) and elderly (n=398 or 80.4%) interviewees believed that consanguineous marriages were no more durable than non-consanguineous marriages (p=0.578). Additionally, 408 (82.4%) of the elderly individuals and 108 (80.6%) of the students recognized that spouses in consanguineous unions experience conflicts, just like other couples do (p=0.625). In both groups, the majority of the participants did not believe that consanguinity increased the risk of having children with disabilities. The regression of the two continuous variables ‘age’ and ‘positive attitudes score’ showed a significant correlation, suggesting that younger individuals are more susceptible to the influence of cultural factors contributing to consanguinity, such as the opinions of their parents and grandparents. The belief that consanguineous unions are more durable showed a significant difference between elderly individuals in consanguineous and non-consanguineous unions (p=0.001); the former were 2.42 more likely to believe that marriages between relatives contributes to marriage durability.

The effects of marriage between biological relatives on the incidence of childhood genetic illness and mortality are of major policy significance, as rates of consanguinity exceed 50% in various countries. Empirical research on this question is complicated by the fact that consanguinity is often correlated with poverty and other unobserved characteristics of households, which may have independent effects on mortality. This study has developed an instrumental variables empirical strategy to re-examine this question, based on the concept that the availability of unmarried cousins of the opposite gender at the time of marriage creates quasi-random variation in the propensity to marry consanguineously. Using primary data collected in Bangladesh in 2006–07 and Pakistan in 2009–10, the study found that previous estimates of the impact of consanguinity on child health were biased and falsely precise. The study also empirically investigated the social and economic causes of consanguinity (including marital quality) and concludes that marrying a cousin can have positive economic effects for one’s natal family, by allowing deferral of dowry payments until after marriage.

We challenge the classical belief that products of degenerate quadratic forms must remain degenerate and we show that this fails in general, e.g. over tensor triangulated categories with duality. This opens new ways of constructing non-degenerate quadratic forms and hence classes in Witt groups. In addition, we encapsulate in a Leibniz-type formula the behavior of the product with respect to the symmetric cone construction. We illustrate these ideas by computing the total Witt group of regular projective spaces.