The populations of indigenous societies which were decimated by their first contact with outsiders can recover over time, according to "Crash and Rebound of Indigenous Populations in Lowland South America," a new report published in Nature.
Note: "Using a method called population viability analysis, the researchers found that contact by outsiders is typically catastrophic, yet survivable. While first contacts in Brazil led to population declines of 43 percent on average, that decline bottomed out an average of eight or nine years after contact, following which population numbers grew as much as four percent a year -- about as much as possible. Projecting those results into the future suggests that contacted and as-yet uncontacted populations could recover from a low of just 100 individuals." Source: The Santa Fe Institute.
Comment: Some of the headlines I've seen about this study are misleading because they suggest that indigenous cultures which have been living in isolation from the modern world can recover from their first contact with outsiders. That's not accurate, however, because the report only deals with population numbers, not with tribal cultures. The mindset and way of life of a primitive tribe can't survive the first contact with a more advanced civilization. Once they lose their isolation, these tribes are finished.
Every now and then, reports surface that a new "uncontacted" tribe has been discovered somewhere. For example, the signs of one such tribe were discovered in the Amazon back in 2011. Another tribe, the Kawahira, lives in the Brazilian jungle (it might even be the same tribe for all I know), and there are more of them scattered around the planet. Various organizations have been set up to try to protect these groups and preserve their lands, but there's a big difference between "uncontacted" and "undiscovered." Even if we never contact them, the tribes we know about are monitored and photographed from a distance while living in their natural habitats. It's hard not to see them as zoological specimens contained in a biological preserve.
These tribes are all doomed, of course. Left alone, they're little more than zoo animals living in a time warp, cut off from modern medicine, education, etc. Contacting them, however, is like dropping an atom bomb on their way of life. If their populations recover over the years, they will simply be absorbed into the masses scratching out an existence in the streets of one of our modern hive cities. All things considered, leaving them alone is probably the best option, but you have to wonder how long their artificial isolation can last.
Still, I kind of envy people who have never heard of "civilization."