For centuries, slow and inefficient oxen had pulled most plows. They allowed farmers to increase the horse's load and reduce plowing time. Together with waterwheels, and later windmills in low-lying countries, this led to more efficient farming and the greater specialization of jobs. Less time needed for plowing made it possible for peasants to live farther from the fields, fueling the growth of cities. But the most important effect of these early steps toward harnessing energy was to make the rest of the millennium's energy achievements possible.
Technology gives birth to further technology.
Coal started to replace wood, both because it packed more energy and because forests were becoming depleted in some areas. As miners dug deeper into their deposits, flooding from underground water became an increasing problem. Aware of the high cost of using horse power to pump water from the Cornish mines, Thomas Newcomen, an English purveyor of iron goods, developed a steam engine to do the job. But it was James Watt's insight that really got the engine moving. One day, while repairing a Newcomen engine, Mr. Watt, a Scottish instrument maker and inventor, was struck by the waste of steam inherent in the design.