The reason these changes during the agricultural revolution
did not significantly alter our life history pattern was
because energy remained costly and scarce for the large majority
of humans, which in turn resulted in similarly high
fertility and mortality rates. If anything, fertility and mortality
rates on average increased slightly in agricultural systems
in comparison to hunter-gatherer systems [33]. Therefore, all
human life before the modern world was characterized by
15-20 years of "pre-reproductive" life, a post-reproductive
life-span that could last 30-40 years, and an organization
including extensive reproductive support from adult males
and post-reproductive females. This evolved life history
strategy proved best for maximizing fitness.