In Humanities we’ve begun learning how and why our ancestors stopped roaming the Earth as hunters and gatherers and settled down in communities. This was around ten thousand years ago when the sparse population of homo sapiens followed and hunted the great beasts, wholly dependent on them for adequate nutrition. They supplemented their meat by gathering berries and vegetation.

Then came one of the great sea changes in human history: we stopped moving. We settled in communities and began farming and raising livestock. This set the stage for the rise of the first great civilizations in Mesopotamia, Egypt, and China.

But to accomplish this men and women had to master irrigation. Farms large enough to support growing communities are not usually possible without it, and our ancestors had a master stroke of ingenuity when they discovered how to move the water to the soil.

Grade 6 spent some time independently researching irrigation–how it works, why it’s important, examples–before coming to class. I challenged them to show me how they understood irrigation with a tool typically reserved for the kindergarten classes: play dough. Working in two groups, the students demonstrated the basic principles of irrigation by molding the colorful clay and then explaining to the other group how their model worked.

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