The Economist explains:
The killer application that led to humanityís rise is easy to identify. It is agriculture. When the glaciers began to melt and the climate to improve, several groups learned how to grow crops and domesticate animals. Once they had done that, there was no going back. Agriculture enabled man to shape his environment in a way no species had done before.
In truth, agriculture turned out to be a Faustian bargain. Both modern and fossil evidence suggests that hunter-gatherers led longer, healthier and more leisured lives than did farmers until less than a century ago. But farmers have numbers on their side. And numbers beget numbers, which in turn beget cities. The path from Catalhoyuk in Anatolia, the oldest known town, to the streets of Manhattan is but a short one, and the lives of people today, no matter how urbane and civilised, are shaped in large measure by the necessities of their evolutionary past.
Think about this for a moment: up until less than 100 years ago, hunter-gatherers still led longer, healthier, and happier lives with more leisure time (on average) than people in sedentary, agricultural communities. If their lives were so much better, whey didnít their lifestyle come to dominate the world? Because that lifestyle doesnít allow for having as many children.
Farmers had more children; those children created more agriculture communities and, over time, these communities pushed out the large areas needed for hunter-gatherer communities. Hunter-gatherer communities lost not because they were inferior in terms of living well, but because they didnít have enough kids. This makes sense from an evolutionary standpoint because the more members of a species there is, the less likely a disease will be able to wipe them all out.
On the other hand, did we humans really come out better because of this bargain?