Some people I know are passionate about their Irish heritage and are “black Irish” — i.e., they have dark eyes and hair and, sometimes, a more Mediterranean complexion. One theory is that they are descendants of Spanish sailors who were stranded on the Irish coast in the 1500s. Another is that they can trace their roots back to one of the countless invasions by Vikings or Normans over the centuries.

I don’t begrudge anyone who wants to investigate how their people came to Ireland. But why would you throw away your culture and identity because five, 10, or 20 generations ago your great-great-great-great-great-great-grandfather or grandmother came from somewhere else? Many Italians have a smorgasbord of DNA in them — from the Moors or other invaders. Are they not “real Italians”?

There’s a term for this kind of thinking: “racial purity.”