Where did the Kurgan (Indo-European) people come from? (Eller, 2000)

"The question of where the Kurgans came from has a rote answer: the
Russian steppes. Gimbutas has brought great precision to questions of
the Kurgan homeland. She centers it in southwestern Russia where the
Don and Volga rivers approach one another most closely, extending
downward from there toward the northern shores of the Black Sea and
eastward toward Kazakhstan and the northern shores of the Caspian Sea.
Rhetorically speaking—part from the any archaeological data
confirming or disconfirming this theory—this is a terrific place to
locate the patriarchal homeland. What is requires is a territory big
enough to be home to a largish population of marauding warriors; a
place from which one can, without crossing enormous geographical
barriers (such as oceans) reach Europe and the Near East; a region
whose prehistory is neither noble nor well documented; and finally,
since no one wants to come from the place where patriarchy began, a
land this is sparsely populated today. On all counts, the Russian
steppes—"no man's land"—fit the profile (Eller 2000, p. 49).

"In short, the case for the spread of the Indo-European speakers from
the Russian steppes is merely suggestive—and the argument that this
spread occurred via military conquest is completely speculative—though
not entirely implausible (Eller 2000, p. 166)."

Eller, C. (2000). The myth of matriarchal prehistory: why an
invented past won't give women a future. Boston: Boston Press. ISBN
0-8070-6793-8