I have only begun reading this, but I've saved it for tomorrow. I enjoy these types of reads. Recently, cliffelam made this post about a russian family that was cut-off from human contact for 40 years. They figured that man had been able to send things in to space when they saw "stars moving across the sky" etc. -Some cool insights and a really enjoyable read.
When I was in Australia last year I heard of regular "discoveries" of lost tribes of aboriginals throughout the last 50 years. Most of them have "discovered" modern civilization but chose not to get involved. Their beliefs are so riddled with taboos and self inflicted punishments that they shun other people even if it could save their lives. About the latest tribe, found in 2008: http://en.wikipedia.org/wiki/Pintupi_Nine