On Wednesday, 23-year old Sakshi Mishra circulated a desperate video appeal in which she claimed that her father wanted to murder her and her husband, Ajitesh Kumar. The reason: the couple, who come from different caste backgrounds, had recently eloped. This allegedly enraged Mishra’s father, who is a Bharatiya Janata Party MLA from Uttar Pradesh.

While Mishra’s social media appeal for protection from her father was novel, the phenomenon of violence sparked by inter-caste marriage is depressingly common across India. Just over the past week, two gruesome instances of so-called honour killing have been reported. On Monday, a Dalit man was allegedly lynched by family of his upper caste wife in Gujarat. On Thursday, a man and his pregnant wife were hacked to death in Tamil Nadu again for marrying across caste lines.

Caste is India’s greatest social evil and endogamy – the practice of limiting marriage within one’s community – is the way in which this social structure is sustained. As is clear from the frequent examples of so-called honour killings, caste endogamy is critical to Indian society and failure to follow it can result in even the extreme act of parents murdering their own children.

Not only is caste a core feature of Indian society today, it has endured for thousands of years. Genetic research has found that the concept of caste endogamy is between 2,000 to 3,000 years old in the Indian subcontinent. As a result, even though India is densely populated, its 4,000 caste groups are genetically distinct, given that caste rules have meant strict social isolation from their neighbours.

Incredibly, modernity does not seem to shake caste endogamy in India. Research conducted by Tridip Ray, Arka Roy Chaudhuri and Komal Sahai at the Indian Statistical Institute, Delhi shows that despite massive socio-economic changes, caste endogamy has remained stable for the past four decades. Moreover, it seems that urban households do not have a higher probability of inter-caste marriage than rural ones.

To add to this, a study by researchers Kumudini Das, Kailash Chandra Das, Tarun Kumar Roy and Pradeep Kumar Tripathy shows that caste endogamy is also unaffected by industrialisation. Highly industrialised Tamil Nadu, for example, has one of the highest caste endogamy rates in India at 87%.

As a result, as per the latest census data, the rate of inter-caste marriage in India was just 5.8%. Between 2001 and 2011, 19 out of 20 marriages in India were still conducted as per an ancient system of birth-based caste.

The endurance of caste and the discrimination it engenders has been disastrous for Indian society.A Dalit child is 42% more likely to die in its first year than if he had been born upper caste. A Dalit woman in India has a life expectancy of just 39.5 years, nearly 20 years less than that of an upper caste woman. To put this in perspective, Dalit female life expectancy in India is more than ten years lower than the female life expectancy in Sierra Leone, the country with the worst life expectancy in the world.

The paradox inherent in Sakshi Mishra’s video was not lost on viewers. In 21st-century India, a young couple was using a smartphone – an instrument that has come to define the technological advancement of our time – to inform the world about how an ancient practice had put their lives at peril. India cannot afford to ignore the horror of caste any longer.