I start reading this haplogroup stuff, and I really try to stay awake. I really do, but generally loose. They have to do a better job of explaining it to non- post doctoral genetics scientists.
From this article, it's clear my Paleolithic Hunter-Gatherer ancestors ("I" haplogroup) didn't do a very good job of vetting the Anatolian Farmers and Steppe dwellers who invaded and overran Europe way back then.
Of course, climate change played a part. If not for the end of the Ice Age, the invaders wouldn't have wanted to invade.