This guy or lady or guys and ladies seems to have had a theory to prove and went out and proved it... And they did not read history of the Germanic Invasions — nothing much to do with Germans directly - but the hoards of people in waves of invasions including, the Goths, the VisiGoths, the Burgundians, The Barbarians, The Allans, Angles and Saxons, Franks and numerous other tribes. then the Vikings who went into what is now Ireland and Scotland but the migrated down the Volga far into Russia. Oh and those pesky Romans and earlier Greeks who had Mediterranean blood from every peoples that touched that great sea... And what a non revelation that Ukraine would be included — ever heard of the Caucasus Mountains as in Caucasian. It is amazing what one can come up with when one leaves out 2500 years of history. I call this Bunk a project to prove a PHD thesis And it has been known for many years that the languages of Europe and subsequently English had elements from very early India - as in Aryan. Wow - what passes for discovery. I noted that this study did not mention comparison to modern Europeans - even those who could trace ancestry for hundreds and hundreds of years in one place. Early Europeans and residents of what is now the EU and the U.K. of even 1200 years ago most likely had DNA from the entire known world of Euro-Asia-Africa... not just some farmers from the steppes of Russia and a few others. Rated again Bunk.
The study is about the first people to come to Europe-- between 45,000 and 4,000 years ago-- way before the historical eras you are talking about (i.e., this study is about where the ancestors of all those peoples you mention came from).