"In order for nimble hunter/gatherers to survive climate change, most must die off periodically to maintain the balance. Farming prevented this kill off. We can return to be hunter/gatherers if we will accept high infant mortality, short life spans, and the loss of ten thousand years of accumulated knowledge."
True. Along the same lines. We have these great immune systems. Where did they come from? From natural selection, which is to say, massive and continual death. What effect do you think modern medicine is having on our immune systems? They will quickly atrophy, like any system not needed.
Actually the first worlders OVER USE of antibiotics, (for example in laundry, dish and body soaps)it is actually weakening our immune systems while disease continues to morph and spread among third worlders to only become a strain that the first worlders have to re-address...