OK, there's the Riverdance type stuff and there's sean-nos, and sure, they're Irish. However, I'm seeing videos on YouTube of Appalachian, Cape Breton, and Acadian step-dancing, and there's always the same person making the comment that it's all been pinched from the Irish.

Did Irish dance-masters flock in huge numbers to French, Scots, and Ulster-Scots colonial territory just to make sure they were all dancing from the same page?

Does anyone know the truth?

My feeling is that there's a common folk root going back a L O N G time - given English clog-dancing and Welsh step-dancing, and it's just that the Irish have a great publicity agent that the rest of us should hire. ;)