Humans arrived in Europe 45,000 years ago and replaced the Neandertals-Neanderthals. There were lots of climate changes from then on including the last ice-age.
Before the last ice age 11,000 years ago people survived by hunting and gathering in Europe. The idea of farming came from the Near East over the last 9,000 years. Modern Europeans are not evolved from these people as far as dna is showing.
Skeletons have been tested for their dna. The first farmers probably migrated into central and eastern Europe about 7,500 years ago. They brought domesticated plants and animals with them. 82% of mtDNA found in the hunter-gatherers are rare in central Europeans today.
The Carpathian Basin has been identified as the origin for early Central European farmers. Farmers of the Linearbandkeramik culture immigrated from "modern-day Hungary about 7,5000 years ago into Central Europe but didn't mix in with the local hunter gatherers. They had cultural contacts but didn't mix in with the women.
Read: Jean M. Auel's books:
The Clan of the Cave Bear about Ayla, Jondalar and Ranec, characters in her books.
The Valley of Horses
The Mammoth Hunters