Doesnt even culture develop in isolation? take for example the aspect of language. Our world has so many languages, which developed at the time when there was very little communication. If communication was very smooth, like today, only handful of languages dominate. New languages are not evolving and older ones are getting diluted. If information flows smoothly, cultural trends spread very quickly. There would be small mini-trends which never get chance to evolve. Isolation would help people evolve and refine these mini-trends, evolving as cultural trends.

I am not a isolationist. Just stating observation.