Proponents of the Indo-Hittite hypothesis claim the separation preceded the spread of the remaining branches by several millennia, possibly as early as 7000 BC.
This is a matter of terminology, though, as the hypothesis does not dispute the ultimate genetic relation of Anatolian with Indo-European; it just means to emphasize the assumed magnitude of temporal separation.
According to Craig Melchert, the current tendency is to suppose that Proto-Indo-European evolved, and that the "prehistoric speakers" of Anatolian became isolated "from the rest of the PIE speech community, so as not to share in some common innovations.
According to another view the Anatolian subgroup left the Indo-European parent language comparatively late, approximately at the same time as Indo-Iranian and later than the Greek or Armenian divisions.
[6] Recent paleogenetic studies of population migration reportedly give new credence to Proto-Indo-Anatolian theories,[7] but several linguists have disputed this and believe that genetics cannot accurately describe historical language change.