A very recent study takes a look at the Pre-Indo-European peoples of
Europe.

For background, there were 2 distinct groups of people in Europe before the
spread of Indo-European speakers from the Steppes: Hunter-Gatherers, and
Neolithic Farmers from Anatolia.  

The study looked at ancient skeletons from Europe to get a better idea of
how much these 2 groups interacted and mixed.  What they found was a high
degree of mixture in France, which was not as prominent in other parts of
Europe.

This may seem like a relatively simple and benign finding, but there is a
lot that is unknown about these people and thus any information about them
is valuable.  These are the people that built Stonehenge, Newgrange, and
the dolmens across Europe.  We know little of their culture and religion. 
And we all carry some of them as ancestors.  So take a minute to read about
them.

https://archive.is/cL4XK

-Hariwulfaz