While it's true that the rate of acceleration is ever increasing, in truth the fundamental break with past societies and our social engineering through capital and media began in the 19th or century, with the groundwork laid earlier. There is far less daylight between the 1890s and the 1990s than there is between the 1890s and the 1490s. This isn't "Conquest of the Planet of the Apes," a nuclear bomb does not throw you backwards down linear time. A nuclear war rather throws your development 'backwards' in some sense, but development is not linear to begin with. It varies widely over time and place depending on innumerable circumstances. If all of industrial society were destroyed, 99.99% of people (meaning 99.99% of experts) were killed, you would not just magically end up in the Victorian era, at least not in all cases. Even for what little knowledge and materiel is preserved in some groups, you may not necessarily have the means or time to actually implement it, you're instead going to have to focus your resources on relearning lost arts and basic survival. I may understand the basic principles behind a steam engine, but am I really going to waste time worrying about it when I'm not even sure where my next meal is coming from? And what about the 6,000 year old tradition of metallurgy that I will have to relearn first to get to that place, all the resources I need to gather? And I also want to note that the traits exhibited by Fallout tribals are not particular to American Indians. Rather, American Indians share similar traits with low-development indigenous peoples the world over, because these are tendenciesand traits very fundamental to how human beings organize themselves. Further food for thought: Across almost the whole of the Americas, the Indians of 1492 were substantively more advanced then those encountered in the 17th and 18th century by Europeans. Disease reached most native societies well before any European set foot there. Disease killed insane portions of the population, breaking down all technical and cultural infrastructure. American Indians as we generally understand them are people who underwent an apocalypse and coped with it. Better still, their adoption of more modern technologies without being able to reproduce them in most cases is a good case study on how a post-atomic tribe would deal with a schizophrenic mix of high and low technology.