There's always wikipedia:

http://en.wikipedia.org/wiki/Life_expectancy

The first subsection is "variation over time". The drop between the paleolithic and neolithic coincides with the development of agriculture.

This is a pretty contentious issue. The idea that humanity's single most (evolutionarily) successful technology caused a massive decline in individual quality of life is pretty disturbing, and some of the evidence is contradictory. It seems like a debate best left to experts, but I thought it was worth mentioning.

I still agree with the original post -- we're very lucky to be alive now.