From the GPSO blog:
A seldom discussed, tragic consequence of human population growth is the loss of tribal cultures and peoples. It is the loss, as well, of ways of life which persisted for nearly all of human history until our population exploded in the last fraction of one percent of our time on Earth.
If anyone participating in GPSO wants to to speak out on one of the most underreported consequences of the growth of the human population, this would be a good choice.
An excellent source of information is the site of Survival International.
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I would add that Survival International seems to say little about the obvious, fundamental link between population growth and the loss of tribal peoples. I suspect it's a sign of how powerful the taboo against mention of overpopulation has been. I hope they'll feel freer in the future to talk about it. It's hard to imagine any hope for tribal cultures if the rest of the world's population grows much bigger.