I think Tinkers & Travellers were probably hard working & the life-style they led must have made them quick witted.I'll bet also if you lived in a small village there would be as much inter-marriage as there was with the travelling folk.layabouts with health problems
When I worked many moons ago with Save the Children I worked with the Travelling community-they were maybe not "educated" in the conventional sense but were mainly intelligent,healthy & fit.Not much couch potating amongst them.