Even when there are mountains of evidence of all different sorts that it took place? Pfft! The change in art and pottery alone is a huge indicator, and that's before you start taking other things into account like settlements where all the men were Kurgan and all the women were not (because the Kurgans killed all the men and children and took the women as war prizes). The Kurgans literally worshipped their swords.

But by the fifth millennium B.C.E., or about seven thousand years ago, we begin to find evidence of what Mellaart calls a pattern of disruption of the old Neolithic cultures in the Near East.5 Archaeological remains indicate clear signs of stress by this time in many territories. There is evidence of invasions, natural catastrophes, and sometimes both, causing large-scale destruction and dislocation. In many areas the old painted pottery traditions disappear. Bit by devastating bit, a period of cultural regression and stagnation sets in. Finally, during this time of mounting chaos the development of civilization comes to a standstill. As Mellaart writes, it will be another two thousand years before the civilizations of Sumer and Egypt emerge.6 (emphasis mine)

Eisler, Riane. The Chalice and the Blade (p. 84). HarperCollins. Kindle Edition.