"The Steppe hypothesis posits that Indo-European spread out of the Pontic- Caspian Steppe, no earlier than 6500 years before present (yr B.P.), and mostly with horse- based pastoralism from ~5000 yr B.P. (Fig. 1B). The farming hypothesis claims that Indo- European dispersed with agriculture out of parts of the Fertile Crescent, beginning as early as ~9500 to 8500 yr B.P.. Linguistic reconstructions of some PIE lex- icon, and ancient contacts with early stages of the Uralic language family, have been widely interpreted as supporting the Steppe hypoth- esis, but the interpretation of these data is controversial."