Well, no G-U1 was found in Neolithic Europe so far, neither G-M406. Let's see if some sample shows up in the near future. Anyway, the "Caucasian" branch of G-U1 seems to be G-L1266. The TMRCA (Time to Most Recent Common Ancestor) of G-L13, which is spread in Europe and Middle East, is 5000 ybp according to YFull*, so after the beginning of the Bronze Age in (SE) Europe. Its arrival looks to me to have happened in the Bronze Age then. Unless you think the G-L13 MRCA lived somewhere in Eastern Europe and spread to Middle East, in the fashion of clades as R-Z2103?
*Older clades' have higher accuracy due to the higher number of samples used for age calculation.