Dunno if this helps, but Britannica Concise Encyclopedia says:

Family of languages with the greatest number of speakers, spoken in most of Europe and areas of European settlement and in much of southwestern and southern Asia.

They are descended from a single unrecorded language believed to have been spoken more than 5,000 years ago in the steppe regions north of the Black Sea and to have split into a number of dialects by 3000 BC.