My understanding of the impact of the Younger Dryas is that the prior warming had led to greater northern reach of flora and fauna, extending the human bounty northward into Eurasia whose populations subsequently increased.
The sudden cooling of the Younger Dryas forced a concentration of these humans and their food supplies into the mid-east latitudes, still plentiful, resulting in settlement and, next, farming.
Am I at least treading water here?
It must have been disruptive, at least, but there was still a lot of glacial cover over higher latitudes and altitudes.