This map here shows the evolution of languages in Great Briton. One of the things I found weird about it though is that it shows Irish slowly spreading through Scotland and replacing the previous language there, Pictish. I didn't know much about the language of Scotland, so I had never heard of this happening.
What's the history behind this? What happened with Ireland in Scotland? Was there just a lot of migration? Did Irish peoples just conquer Scotland? Did Pictish influence Scottish Gaelic at all, or was the original language of Scotland completely replaced with Irish?
What about modern efforts to revive/preserve Scottish Gaelic? I know it's considered a part of the modern Scottish identity, but this map makes it look like it's a foreign language to Scotland as well. Does anyone know more about the history behind this map or the languages of Scotland?
The Picts are generally supposed to have been a Brittonic Celtic people, more closely related to the Welsh and Cornish than the Irish. This is difficult to completely verify, though, because the only traces of the Pictish language that have been preserved were in the form of names: of places and people.
By the 4th and 5th centuries, though, western Scotland came to be dominated by Gaelic speakers. How this happened is unclear. The traditional account was that Irish Gaels began migrated to the area during this time, but archaeological evidence is lacking, so how Gaelic speakers ended up in Scotland is a mystery. The archeologist Ewan Campbell has suggested instead that perhaps western Scotland had always been closer, culturally, to Ireland than the rest of Scotland.
Regardless, over the centuries, warfare became common between the Picts and the Gaelic-speaking kingdom of Dalriada. Though the Picts most frequently triumphed in military terms, it was the Gaelic language that begun to spread wildly. How this happened is not entirely clear. The origin of Kenneth MacAlpin, often considered the first king of Scotland, is unclear. No one is certain whether he was a Gael, Pict, or mixture of both. What is certain that Gaelic was not spoken in all of Scotland; there is little evidence, for instance, of it ever being widespread in the Southeast.
If you're thinking that's way complicated, we're only getting started because this was also the era of Viking invasions in the North. Meanwhile, in the 11th century, Malcolm III married an Anglo-Saxon princess, Margaret of Wessex and the Norman kings claiming dominion over Scotland and intermarriage between them (Henry I married the daughter of Malcolm III and Margaret) also meant an increase of their influence as well.
DNA tests on modern Scots have indicated that they are, on average, 43.84% Irish, 26.18% British, 13.05% Western European, and 7.19% Scandinavian. There is no reason to think, therefore, that the Picts were exterminated or whatever. It's more likely that the identity simply faded out and the people absorbed into Gaelic culture, as the Briton identity faded out and its people were absorbed into Anglo-Saxon culture.