It wasn’t an immaculate conception. After its first hazy origins some 65,000 years ago, the story of Indian languages has been the story of miscegenation, of the mixing of language blood-groups. Sanskrit is as much its child as the old Harappan, or modern Assamese and Malayalam. The traces of that marriage, often conducted on unequal terms, are present everywhere in the swapping of genetic material—especially in the features left behind by an invisible mother. Linguist Peggy Mohan seeks to unravel strands of that mystery in a fascinating new book. Excerpts…