Good point SaronA. Made me think a lot.The pendulum swings between "melting-pot/fusion" and"salad-bowl/separate but equal" have been going on since the year dot. Walk down any street round here and your eyes will show you how distinct physical characteristics have developed in different populations. Listen to music from round the world and your ears will tell you the huge differences in sounds and structurs.
But equally well, you don't need ethno-musiclogical ears to listen to highlife or reggae and hear a totally seamless fusion between European harmony and African sounds and structures. And another look down the same street will reveal mixed families and children who don't follow the patterns you'd previously been noticing. The fact is both theories, and both practises, are universal. neither is more "normal" or "natural" or "better". Any attempt by any group to promote one at the expense of theother is doomed to failure, and cause trouble along the way. Pendulums swing, swings and roundabouts even out. You may get on a roll at roulette by betting on the evens for a while because you think you've spotted a pattern, but it won't last.The odds will come back.