In a strict Darwinian sense I would say no when it comes to humans. Of course, humans are not the only species on the planet - much to the chagrin of the religious fanatics - and evolution continues among isolated populations much as it always has as Dawkins showed in his latest book.
Humans are not really "isolated" and human culture interferes with reproduction and survival anyway.
Humans are not really "isolated" and human culture interferes with reproduction and survival anyway.