"The largest single step in the ascent of man is the change from nomad to village agriculture."

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The most important characteristic of an organism is that capacity for internal self-renewal known as health. There are two organisms whose processes of self-renewal have been subjected to human interference and control. One of these is man himself (medicine and public health). The other is land (agriculture and coservation). The effort to control the health of land has not been very successful.

— Aldo Leopold