Measuring consanguinity on a global scale involves comparing very different realities: marriages between first cousins encouraged by tradition, unions within geographically isolated communities, or practices linked to inheritance logic. The rate of consanguineous marriages varies from a few percent in some regions to a majority proportion in others, with direct consequences on the frequency of recessive genetic diseases.
Rates of consanguineous marriages by country: comparative table
The available data shows a clear geographical gradient. The highest rates are concentrated in the Middle East, North Africa, and South Asia. The table below groups the countries regularly cited in epidemiological studies for their levels of consanguinity among the highest.
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| Country | Level of consanguinity | Dominant type of union |
|---|---|---|
| Pakistan | Very high | First cousins |
| Kuwait | Very high | First cousins and beyond |
| Qatar | Very high | First cousins |
| United Arab Emirates | Very high | First cousins |
| Sudan | Very high | First cousins |
| South Sudan | Very high | Intra-community unions |
These six countries consistently top the ranking of countries with the highest consanguinity. The practice remains socially valued there, sometimes encouraged to maintain family cohesion or preserve land heritage.
In contrast, Western Europe, North America, and East Asia show low to very low levels. The decline of cousin marriages dates back several generations, driven by urbanization, mobility, and sometimes restrictive legal frameworks.
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Cultural and geographical factors behind regional disparities
Geography alone is not enough to explain these disparities. Three overlapping mechanisms reinforce each other.
Tradition and customary law
In several Gulf countries and South Asia, marriage between first cousins is seen as a guarantee of stability. The union strengthens ties between branches of the same family and simplifies negotiations related to dowries or inheritance. This customary framework weighs more heavily than medical recommendations.
Geographical and demographic isolation
Enclosed rural communities, whether located in the mountainous areas of Southeast Asia or in certain sub-Saharan regions, mechanically present a very limited pool of potential partners. The choice of spouse occurs within a limited group, which raises the average degree of relatedness between spouses without any explicit intention of consanguinity.
Documented decline in certain areas
Vietnam illustrates an opposite trajectory. In the mountainous areas of the country, awareness campaigns conducted since the early 2020s have reduced rates of consanguineous marriages to a level close to zero, according to a report published by Vietnam.vn in 2024. This result shows that targeted interventions can reverse a trend in a few years.
Health consequences of consanguineous unions on population health
Marriage between relatives increases the likelihood that both parents will pass on the same deleterious recessive allele to their offspring. The effects on public health have been documented for decades.
- Increased frequency of recessive genetic diseases: cystic fibrosis, sickle cell disease, certain congenital deafness, or rare metabolic diseases see their prevalence rise in populations with high consanguinity.
- Higher risk of infant mortality and developmental delays, linked to the accumulation of recessive alleles over several successive generations of cousin marriages.
- Reduction in immune system diversity (HLA complex), which can decrease a population’s ability to resist new infections.
Countries where consanguinity remains predominant thus concentrate a disproportionate share of certain rare pathologies on a global scale. Programs for premarital genetic screening, deployed for example in several Gulf states, aim to inform related couples of the risks without prohibiting the union.
Animal consanguinity and genetic conservation: a cross lesson
The genetic mechanisms at play in humans are amplified in conservation programs for endangered species. The study of human consanguinity has directly informed the protocols used by conservation biologists.
A recent example concerns African elephants. A study published in Nature in March 2024, reported by Science et Vie, documented a rise in consanguinity among African elephants linked to post-poaching isolation. In 17 countries, habitat fragmentation and drastic population reductions have created a “genetic trap”: the surviving populations, too small and too isolated, reproduce among relatives, accelerating their decline.
The parallel with isolated human populations is direct. When a group, whether animal or human, sees its reproductive pool shrink, genetic diversity collapses in a few generations. Conservation strategies (ecological corridors, transfers of individuals between populations) are inspired by the same principles as public health recommendations: broaden the genetic pool to reduce homozygosity.
In the Pyrenees, the management of the brown bear population illustrates this logic. Annual genetic monitoring serves precisely to track the degree of consanguinity and decide on potential reintroductions to maintain the group’s viability.
Consanguinity, whether human or animal, produces the same biological effects: accumulation of deleterious mutations, decreased fertility, increased vulnerability to diseases. Data collected in countries with high rates of consanguineous marriages now feed the population genetics models used to save endangered species.
This convergence between public health and conservation biology remains one of the least visible, yet most concrete, contributions of the study of human consanguinity on a global scale.