> On 14 July 1909, Ramanujan married Janaki (Janakiammal; 21 March 1899 – 13 April 1994),[25] a girl his mother had selected for him a year earlier and who was ten years old when they married.
From what I understand, it was common across many communities throughout India (though in Tamil Nadu, primarily among the Brahmins) for girls to be married before the onset of puberty (with consummation of the marriage only permitted post-menarche.. at least in theory). I do recall seeing a paper once that argued that the age of marriage actually became younger for some complicated reasons under British rule in the early 19th century.. not sure if that's believable.
As you might guess, I'm from the same community, and my great-grandmother was married at the age of 9 or 10. While one could attempt to rationalize and contextualize it, I think that's pointless: it was wrong then, as it is now.
It was a social evil has rightly been banned but slavery was both a social evil and individual maliciousness on part of people who partook in it - and there were a few black folk too in that group who were selling their own people. No society 'mandated' slaverer to sell people as a way of life. There were always other professions if it didn't fit well with their conscience. No one would make your life hell for not actively selling slaves by making you into a social outcast.