Whatever, throughout history there has always been a mass peoples migration due to wars or famine and it couldn't be stopped, even ancient Rome couldn't stop it with violence, the Angles, Jutes and Saxons wandert into Britain as did the so called Vikings which gave way to Dane law in Northern and Eastern England in the 9th century, Scots have a similar genetic make up as the Scandinavians while the English genetics have more in common with the Germans than the Welsh. As more parts of the world become unlivable due to poverty, war and/or climate change there will be an unstoppable human wave during this and the next century moving to more amenable climates. The Zulus caused mass migration in Africa during the last 200 hundred years due to their own territorial expansion so this is nothing new. As the Western demographics continue to be top heavy with old people this can be accommodated and will be, even Japan is now considering immigration as their numbers dwindle.