"In regard to the marriages it may significantly be mentioned that the converts are still following the custom of marrying within the tribal community and for this purpose they have not completely detached, themselves from their old community. An Oraon Christian boy is prepared to marry a non-Christian Oraon girl, but he will not marry even a Christian Munda girl. But in this connection the missions have succeeded in forbidding marriages of Christian girls with non-Christian boys. This has helped the missions to satisfy the traditional instinct of the converts as well as to achieve additional number of converts through the non-Christian girls who are married to Christian boys."
January 1, 1970
https://en.wikiquote.org/wiki/Niyogi_Committee_report_on_Christian_missionary_activities