Grigoryev 's ( 1998 ) version of the Armenian hypothesis connects Catacomb culture with Indo - Aryans .
Catacomb burial ritual had roots in South - Western Turkmenistan from the early 4th millennium .
Grigoryev 's ( 1998 ) version of the Armenian hypothesis connects Catacomb culture with Indo - Aryans , because catacomb burial ritual had roots in South - Western Turkmenistan from the early 4th millennium .