Cousin Marriages : The Risks and the Research
By definition, a cousin-marriage is defined as marriage between individuals related as second cousins or closer. In Pakistan, marriage between cousins is relatively common with 48.5% of married women being related to their husbands as first cousins, and another 7.9% as second cousins. On the other hand, cousin-marriages are frowned upon in many cultures and are legally prohibited in many countries.
The reason behind the disregard for cousin marriages stems from medical research which has identified a higher incidence of genetic defects and serious diseases in children of parents who are cousins.
The scientific explanation behind this is based on the limited gene pool. Many congenital diseases are due to gene mutations. One gene mutation may not produce the disease but when two genes are combined, it can lead to the full-blown defect. These faulty genes may run in families which increases the risk of cousins having the same gene defect. Thus, the risk of congenital defects is multiplied in children of cousins who both have the same gene mutation.
Research was conducted through surveys to understand the reason why Pakistan has one of the highest rates of cousin-marriages in the world. Most Pakistani couples supporting consanguineous marriages felt that their daughter would be treated better if her in-laws were members of the same family. Others felt that in-laws would understand the financial constraints and defer the dowry payments if needed.
In 2010, a study was conducted on “Watta Satta”, a common practice which involves an exchange of brides within two families. This study had surprising results as it concluded that marriage outcomes in rural Pakistan were better in cases of “Watta Satta”.
Less than 10% of the married women were against cousin-marriages and many believed that the spousal relationship is strengthened and the risk of divorce is reduced in consanguineous marriages.
Although the risk of genetic deformities has always been correlated with cousin marriages, a recent study conducted at Yale attributed these medical defects to the other confounding features such as low socioeconomic status and low education profiles which are also common in these families. But even after considering these factors, the rate of genetic illnesses in children of cousins remains 3.3 percentage points higher when compared to unrelated parents.
Many cultures prohibit cousin marriages, not because of medical issues but also because there are ethical considerations which consider cousins to be brothers and sisters, thereby equating cousin marriages to incest.
The debate on cousin marriages may become irrelevant in the future as the rate of inter-cousin marriages has been proposed to reduce drastically in the future. The main reason behind this is that couples today are more aware of family planning. This has reduced the overall fertility rate and birth rate, which will mean that in the future, all families will have a lesser number of children, which will consequently mean a lesser number of cousins will be available to marry each other.
In general, marriage decisions are decisions based on feelings rather than scientific facts. The families of both the bride and the groom consider many factors before finalizing the wedding, but genetic mutations is not one of them. The idea of pre-marital genetic testing is nonexistent and any disease which follows is attributed to fate rather than a preventable condition.
Keeping this in mind, convincing the average population about the medical risks of cousin-marriages will not be an easy task. Educational campaigns should be targeted at families with a significant family history of genetic malformations so that they can help prevent others from making the same mistake.
Estimating the health and socioeconomic effects of cousin marriage in South Asia
Mobarak A.M, Chaudhry T, Brown T, et al
Journal of Biosocial Science (2018)