- Then small tribes never existed, and island cultures are imaginary. The people alway die out, right? Riiiiight. We'll just ignore the idea that there are whole worlds that could be expanded into, so it needn't remain tiny forever, nor do the people need to be huddled together all the time.
- Oh, let's see now. I talk about civilisation falling apart, and you wonder how infrastructure will disappear. And since moving supplies is so expensive, don't expect 'raiders from Earth, either. Duh.
You confuse science fiction with fantasy set in a technical background. Science fiction has a funny tendency to come true in one form or another. We WILL go to other worlds to live, despite your reactionary 'don't go! It's DANGEROUS out there' attitude. I truly hope that we do it fast enough to preserve us through what I think is to come. Your way, social collapse and the 'social evolution' (talk about fantasy!) preserves nothing and leaves the door to the death of humanity as a species even wider.
edit: damn that title was harsh