All the following passages are then wrong, but they almost got it right.
There are 3 Caucasian Races:
1. European Hunter Gatherers (divided into 3 groups, Western(WHG), Scandinavian(SHG) and Eastern(EHG))
2. Caucasus Hunter Gatherers
3. Mediterranean Farmers

A. The original inhabitants of Europe were the European Hunter Gatherers.
B. Then came the invasion of the Mediterraneans in the Neolithic. Initially they genocided the European Hunter Gatherers and mixed very little, but throughout millennia, the Hunter Gatherers reclaimed territory and increased their fraction of ancestry in the population by mixing more. These people are known as EEF (Early European Farmers).
C. Then came the Aryans (Yamnaya, Indo-Europeans), which were a mixed 50/50 Eastern European Hunter Gatherers and Caucasus Hunter Gatherers. They invaded Europe from what’s now Ukraine. Then Corded Ware appears and continues East and Westwards. They would subsequently migrate to all of Central Asia, Persia and India. Europeans today are the product of said time, varying from being about 25% Aryan + 75% EEF to being 50% Aryan + 50% EEF. Of course, rough numbers.

The Original Middle Easterners were as follow:
1. Mesopotamian: 75% Caucasus Hunter Gatherer, 25% Mediterranean Farmer
2. Canaanite: 50% Caucasus Hunter Gatherer, 50% Mediterranean Farmer
3. Egyptian: 25% Caucasus Hunter Gatherer, 75% Mediterranean Farmer

Of course, I’m being very simplistic, but that’s the story. Today, specially after the end of Roman times and the rise of Islam, the Middle East saw a huge amount of Sub-Saharan African slaves and admixture. Same thing for the Aryans of India and their Dravidian neighbours, and Central Asia with the Turks and Mongols.

You could say that the “European/Aryan World”, genetically speaking now, peaked in the Bronze Age, and after that it started collapsing due to other people migrating (ironically, people who received Aryan technology and way of life, which is clearly the case with the Turks and Mongols, for instance).

The 7th Century was when the downturn happened for good and never bounced back again.

A while ago the BBC aired a special on the history and evolution of Stonehenge. They completely missed the racial turnover at the site and attributed all the radical cultural changes evident there to endogenous developments. No Indo-Europeans for them, either.