Found this on Slashdot: seems that, statistically speaking, isolated Amazonian tribes have a huge population crash shortly after first contact with the modern world.
A quick skim doesn't turn up a reason. Like, are a lot of the individuals dying off in the first year, due to exposure to new diseases to which moderns have better immunity? Are they committing suicide after discovering that they aren't the master race after all? What?
But, no clues offered. Just: the population declines dramatically. It's all collective. The tribe dies off.
Which is the same thing that would happen if all the young'uns ran off to the big city to see the amazing new world that had just discovered them.
So... are individuals dying, or leaving, or just losing their tribal identity? From the individualist perspective, there's a huge difference. To a collectivist, it's all about the tribe, and what's happening to the individuals is of no consequence.