DNA information is still in its infancy, nd TV programmes tend to draw some big conclusions from small statistical differences. Small numbers of invaders(or peaceful colonisers) can also make a huge cultural difference in spite of tiny numbers. Look at the Normans in England and Ireland, or the British in India or Africa. but itis intriguing as McGrath points out there dont seem to be that many stories/legends/historical account of just what happened from a non-Gaelic situsation in Scotland in say 300AD to 500years later when a big chunk of the area was covered with Gaelic place-names, inhabited by Gaelic speakers with Gaelic names and ruled by Gaels. Two people have postulated a peaceful(or near peceful) process. I ahve my doubts. There is some account in the late Romano-British period of the start of the raids, but after that things go very vague. I agree, you would expect the Gaels (being a touch on the lively side when it comes to warfare) would have made a song and dance boasting about it. I'll have to look into this further, it's intriguing. Mind you, the English havent left many poems about their successful battles when arriving in England, but arrive they certainly did, and I doubt if that was a friendlt city-twinning ceremnoy either.