What's interesting is that the population remained isolated for tens of thousands of years. Generally speaking, people move around and are promiscuous. Staying

What's interesting is that the population remained isolated for tens of thousands of years. Generally speaking, people move around and are promiscuous. Staying isolated for that long implies a physical barrier, because cultures generally don't survive for 40,000 years. But an isolated population means genetic issues - but if the population is big then they should have spread at least somewhat.