Manohar Lal Khattar, the chief minister of Haryana, has said the opposition of khap panchayats to marriages between people of the same gotra has a scientific basis.
Khap panchayats – community leadership organisations typically organised along caste lines, have been known to vigorously oppose same-gotra marriages in the villages of India’s north and have often advocated violence against them as well.
Same-gotra marriages are also known as intra-clan marriages (not to be confused with intra-caste marriages). All people who have descended patrilineally (i.e. from father to son) from a common male ancestor are said to belong to the same gotra. Another equally popular – but looser – definition identifies people who followed one of the seven holiest sages of Hinduism, so these people are bound more by their ancestors’ purported philosophical paths than by blood.
Either way, people of the same gotra are said to form an exogamous unit: a coherent social group marrying inside which is considered incestuous. (On the other hand, intra-caste marriages are encouraged.) However, such a prohibition does not carry scriptural authority and therefore lacks recognition in laws concerned with Hindu traditions.
For example, one panchayat convenor, Naresh Kadyan, had petitioned the Supreme Court around 2010 to amend the Hindu Marriage Act of 1955 accordingly. The court directed him to approach the Delhi high court instead. When he did, however, the high court summarily dismissed his petition in June 2010. According to The Hindu‘s report from the time:
… when the Bench asked [Kadyan] to cite any Hindu scripture which bans marriage within the same gotra, the petitioner failed to quote any. Observing that the petitioner was wasting the precious time of the court, the bench said when he could not substantiate his submission he should not move a court. … [The] vacation bench of the court, comprising Justice S. N. Dhingra and Justice A. K. Pathak, warned that it would impose a heavy cost on him if he persisted with his preposterous argument.
The Supreme Court has held that if two people wish to marry, they only need to be consenting adults.
Khattar’s appeal to science for the khap panchayats’ stand is similarly dubious. For one, a marriage is a socio-cultural construct that does not arise from scientific principles, nor do these principles interfere with sexual relations (notwithstanding individual medical conditions) per se. Science itself, in the form of consanguinity, becomes involved when two people have sexual relations with a view to conceiving a child.
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A number called the degree of consanguinity is often used to define the extent to which two people are related. It is calculated using the number of generations before which the latest common ancestor of two people appears. Among all animals, for example, an inbred strain – corresponding to a degree of 0, the closest relationship – appears after 20 successive generations of inbreeding (i.e. sexual relations between brother and sister or parent and offspring).
Among the subset of humans, and using the first definition of gotra: Most laws disallow marriages between people whose degree of consanguinity is 4 or lower, which includes double first cousins, half first-cousins, aunts and uncles, nephews and nieces, half-siblings, grandparents and grandchildren, sibling cousins, siblings (brothers and sisters), parent and offspring, identical twins and all people with an inbred strain.
Mathematically, a degree of 4 means two people had a common ancestor at least four generations ago and have had no common ancestors since. A degree of 10 means they had a common ancestor around nine generations ago and no common ancestors since.
In the realm of clinical genetics, consanguinity is not favourable because the offspring of two people with similar near-ancestors is much more likely to inherit a harmful gene and is less likely to be able to fight off biological threats thanks to their lower genetic diversity (a.k.a. the founder effect).
However, a union is said to be consanguineous if the two people have a degree of consanguinity of 6 or lower, i.e. excluding third cousins and fourth cousins. But at the level of a fourth cousin, the degree of consanguinity nears 10; when two people are half-fourth cousins, the degree is so low that they might as well be genetic strangers.
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All together, since the gotra system operates with a much looser definition of what constitutes an exogamous clan compared to the clinical as well as legal definition of consanguinity, and because of the way the degree of consanguinity is defined, Khattar’s deference to scientific authority doesn’t hold up except with a very small number of cases.
Even then, providing premarital counselling and preconception genetic counselling, which is becoming increasingly more affordable, will have better and more harmonious outcomes than an ill-founded and paranoid blanket ban against marriages or calls for intra-clan couples to be killed.