I added the Brexit bit because of tomorrow's elections.
Subconscious cultural memory may or may not be a thing but I'm thinking 4500 years is pretty close to the event horizon.
From the Guardian:
Did Dutch hordes kill off the early Britons who started Stonehenge?
A gene study has shown that incomers could have ousted Stone Age BritonsFrom what I understand the stone age Britons were much more creative (and flamboyant) than the newcomer Beaker folk:
The men and women who built Stonehenge left an indelible mark on the British landscape. However, researchers have discovered that their impact on other aspects of the nation may have been less impressive. In particular, their input into Britain’s gene pool appears to have fizzled out, having been terminated by light-skinned Bronze Age invaders who arrived just as Ancient Britons were midway through their great Stone Age project. In the end, these newcomers may have completely replaced the people who were building Stonehenge.
This startling conclusion is the result of a huge gene study of humans in prehistoric Europe. It shows that around 2500BC – when the main sections of Stonehenge were under construction – a race of people known to archaeologists as the Beaker folk arrived in Britain. Their genetic profiles were similar to individuals who were living in the Netherlands at the time. In just a short period, all genetic traces of early Stone Age Britons were replaced by those from these continental newcomers, although work on Stonehenge continued.
“It is very striking. There seems to have been a complete replacement of the original folk of Britain with these newcomers,” said Garrett Hellenthal, a statistical geneticist based at University College London. “Normally you get some older DNA surviving with a wave of immigrants, even a fairly large wave. But you don’t see that in this case. Frankly it looks more like an invasion.”
The arrival and spread of the Beaker folk is one of the most intriguing puzzles of European prehistory. These people made complex, very distinctive ornaments in silver and gold and constructed distinctive bell-shaped pots or beakers from which they get their name....MORE