[alternatetwo]

"The Long Earth" series by Terry Pratchett and Stephen Baxter plays with this scenario, by giving humanity access to essentially limitless parallel worlds mostly untouched by humans. You can "step" into a parellel world, and thus eventually hunter gatherer lifestyles come back, since you can just step over once or a couple times to hunt there, and give resources time to recover. The series is quite a good read.