"Every attempt, then, to give absolute dates for 'Proto-Indo-European' (or dates for alleged different stages of'PIE') is either based on the speculative identification of an archaeological culture with the speakers of the 'language of the PIE's' (e.g. Gimbutas, Renfrew, Mallory) or on what may be called 'intelligent guesses,' deliberations of probability and feelings of appropriateness (e.g. Meid, Gamkrelidze-Ivanov)" (372). ... "The first type of proposal is usually contested by fellow archaeologists and doubted by linguists, the second, being purely subjective because objective arguments simply do not exist, is bound to remain noncommittal. As is easily to be seen, many dates of both types have found their way to an often far too skeptical public."
January 1, 1970
https://en.wikiquote.org/wiki/Stefan_Zimmer