I see anthroinsulae all over the world. Countless. These are human islands. Cultures within cultures. Anthroinsulae can keep on dialects and ways for centuries. Little anthropological time capsules. Cultural oil spots that generally get along but do not blend. If there is much intermarriage, the anthroinsula dissolves.
But if the human island is of sufficient size and does not tend to intermarry, you have a little gem. A little time capsule. I’ve been to China towns around the world that seem more Chinese than China itself. Or Tibetans living in Nepal.
Indians who move from the subcontinent to America blend very quickly because we intermarry. Filipinos quickly vanish as we dissolve into each other unless there is a sufficiently large Filipino-town, or they move to, say, Hong Kong where they tend to stay together.
I’ve attempted to make fish-charts of cultures but I get paralysis from knowing too much. In other words, I see exceptions to everything I put to paper. I’ve been with so many cultures that nothing I write down seems to withstand an internal audit other than in general terms.
But I do see some obvious anthroinsulae nearly globally such as Chinatowns, and also Jewish. Chinese will intermarry — obviously and in large numbers — but those who form Chinatowns seem to come from a different sort.