|"Trajes de los indios Moxo"|
With the Moxos and the Chiquitos of South America premature marriages were such a settled order of things that there were no celibates above the age of fourteen for the men and twelve for the women. The Jesuit missionaries in America had completely adopted this native custom, and they often married young girls of ten to boys of twelve years. Naturally these child marriages entailed sometimes equally precocious widowhood. D'Orbigny states that he has seen among these tribes a widower of twelve and a widow of ten years.
In the time of Marco Polo the Tartars of Asia celebrated marriages that were more singular still—the marriages of deceased children. The families drew up the contract as if their children had been living, solemnly celebrated a symbolic wedding, then burned not less solemnly the fictitious contract, which would be, they thought, the means of holding it good in the other world for the vanished young couple. Thenceforward an alliance existed between the contracting families as if the marriage had been real. Among the Reddies of India a young woman from sixteen to twenty years old is frequently married to a little boy of five or six. The wife then goes to live either with the father, or with an uncle, or a maternal cousin of her future husband. The children resulting from these extraconjugal unions are attributed to the boy, who is reputed to be the legal husband. When once this boy has reached manhood his legitimate wife is old, and then he in his turn unites himself to the wife of another boy, for whom he also raises up pseudo-legitimate children. Child-marriages, at least of little girls, are still very common in India amongst the Brahmins, and it is not unusual to see sexagenarian Brahmins marry little girls of six or seven years, for whom they pay money.
Link (here) to The Evolution of Marriage