The recent child mortality cases in the tribal areas of Attappadi may not be just due to malnutrition, starvation or even alcoholism, says population genetics expert P M Mathew. It may have a lot to do with consanguinity or inbreeding in humans through marriages among close relatives that is widely prevalent in the tribal areas, says this former professor of University of Kerala, one of the first from the state to get trained in human population genetics from the University of North Carolina, the US, many decades ago.
Since then, Mathew and his students have been actively involved in the study of over 40 communities, which allowed marriages among blood relatives. Among these 40 populations studied, at least 14 were tribal populations across the state. “When closely related persons marry, lethal and sublethal genes from a common ancestor tend to accumulate in the child and cause problems both before and after delivery. Pregnancy wastage such as miscarriages, stillbirths and early abortions are generally not talked about,” says the professor, who had his students staying in tribal settlements to gain their confidence and collect accurate data.
Among the tribals in the state, the consanguinity levels vary from a 1.5 per cent among Christian Malayarayas (low value because of church ban on related marriages) to a whopping 97.03 percentage among Karuvazhi Pulaya of Idukki. “This tribe exhibits the highest rate of consanguinity in the world, it also has a high rate of mortality. The Mudugar tribe in Palakkad, which has a closely-related marriages rate of 78.74 per cent has a high mortality rate of 37.92 per cent,” says the professor.
The mortality studies had revealed a very high rate of 39.04 percentage in the Paniya group, followed by others such as Adiya, Maratti and Mudugar in the 32-38 percentage range.
Not only mortality, but morbidity also manifested in the form of genetic diseases and mental disorders.
High inbreeding frequencies of 70-91 percentage have been reported in several communities such as Muthuvan, Pallan, Parayan and Irular. “If the population had only good genes, then no problem arises. But often lethal genes find expression through inbreeding. The death of the babies inside the womb or outside is also a means of washing out of the lethal genes from the population, across generations,” says Mathew.
This wash-out procedure is also responsible for reducing the mortality rates in a few tribes even though they have a high frequency of inbreeding. “An enormous amount of data have been generated worldwide on consanguinity. The findings have highlighted a spectrum of harmful effects, from minor defects of vision, hearing and speech, to foetal loss and serious disorders, that makes survival beyond childhood impossible,” says the professor, who is up-to-date in his field of research even 24 years after retirement from the Kerala University.
While debates are on whether it was malnutrition or starvation that killed the children in Attappadi, this population expert is of the opinion that such matters as food and alcohol may have contributed, but that the root of the issue is genetic with blood-related marriages down the centuries causing an accumulation of deleterious genes.
“You can’t give food and wish the problem away. What is needed is genetic counselling and creating an awareness about such risks. The number of close-kin marriages has to be brought down and the age of marriage for women has to be brought up.
Many illiterate tribal women tend to believe that recurrent miscarriages are providential and literacy and awareness can do a lot of good in such cases,” concludes Mathew.