Today, putting horses to work proves harder than we might think. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Western Europe was largely a primitive wilderness until three centuries after the Roman Empire's last gasp. When it emerged as a new civilization, it did so with the help of the new technologies of water and wind power. Europe ultimately did far more with those power sources than the Romans ever had.

But water and wind power had to wait until European agriculture became productive enough to support towns with masons and artisans -- people free to do more than just labor for food. That, in turn, meant we needed a more powerful beast than the plodding ox to pull plows through the heavy, wet Northern European soil. Horses had to be woven into farming before a civilization could emerge.

In the mid 8th century the Frankish kings began breeding horses for military use. But three things kept people from using those horses in farming: Their hooves softened and cracked in damp soil. When they were harnessed in an ox yoke, any heavy load cut off their wind. And horses needed a better diet than oxen. They couldn't just graze grass; they also needed crude protein.

The nailed horseshoe and then the horse collar had solved two of these problems by the 9th century. It was also in the 9th century that people found a solution to the problem of feeding horses. But it takes more than a solution to remove a problem. And that's where the plot thickens.

The solution went like this: Ninth-century farmers used two fields with one active and the other one idle (or fallow.) That kept them from robbing the soil of nutrients and making it unproductive. Then someone discovered they could use a field two years out of three if they planted it with one crop in the fall and a different crop in the spring, a year and a half later.

That meant farmers could break their holdings into three fields. They could plant one with wheat or rye in the fall for human consumption. A second could be used in the spring to raise peas, beans, and lentils for human use and oats and barley for the horses. The third field lay fallow. Each year they rotated the use among the three fields. We remember the spring planting in a nursery rhyme which you may've heard,

Do you, do I, does anyone know,
How oats, peas, beans, and barley grow?

It was a fine, effective scheme, but we took two more centuries to adopt it. While we put horseshoes and horse collars to use right away, three-field crop rotation meant rearranging real estate and changing the social order. Individuals would have to be disrupted before society could benefit. When the shift finally took place, it meant the rebirth of European civilization. By the 11th century three barnyard improvements had amplified and echoed through the medieval world. But it'd taken three centuries to give the horse its place and to build that civilization.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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White, L., Jr., Medieval Technology and Social Change. New York: Oxford University Press, 1966.

See also Episodes 540 and 571 for more recent thinking about the origins of agriculture.

This is a much revised version of Episode 26.