By the way, I see this as legitimately in TMA's remit, the book referred to starts in the Paleolithc and in any case Scotland was effectively prehistoric (i.e. no written records) in the Pictish period too.
If anyone would like to carry on the discussion about Scots/Picts/Celts etc. please feel free to do so here. I for one am interested.
I can't remember where I saw the map but I'm sure that the Western Isles, the west coast of Scotland and northern Ireland were once one nation - going back to the seas being the highways again. I'm guessing what you are talking about is where the people who settled on those islands and coastal areas originated from. I'd love to know because they would have been the builders of Brodgar and Callanish.