The simplest societies tend to have rather high death rates for children, though, and an overall younger population.
Most animals in nature have a pretty high death rate, especially among the young. Humans without technology still have a lower death rate than many other animals, in part because humans have a fairly small number of offspring (typically one at a time, sometimes two, rarely more), so it's not like the many animals whose strategy is to have a ton of offspring and have a few survive. But modern medical techniques improve childbirth survival rate, substantially increase the chances a child will make it to adulthood, and increase the life expectancy of adults.
So there's a trade-off. Technology and complexity brings blessings and curses. In addition to health, technology and complexity have given us things like telescopes, microscopes, safe travel, to allow us to learn more about our world.
I'm not really one to idealize extremely simple societies because based on how my birth went, I'd almost certainly be among those that didn't make it. So I kind of view it like, "Yeah, they do have some advantages. Some disadvantages too. And I'd be dead on arrival anyway.
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