Who is a Jew?

My family on my father’s side was part of the group expelled from Spain during this era. Family history says we were Moors (Muslim) but I have always found it unlikely. Mostly because my family does not resemble Moors (tall and dark skinned). I suppose it was easier to be ex-Moors to ex-Jews in that era. Oddly I live in the southwest now where it appears many converrsos moved here as the New World was settled. A good article from London Review of Books.

Who is a Jew?