Harnessing Heat

Some time around a million years ago, give or take, our early human ancestors (or cousins, maybe—we’re not sure) started playing with fire. Homo erectus undoubtedly came across natural fires at many points, ultimately gradually figuring out how to control and maintain a fire on their own… and then start them.

These fires were mainly basic wood fires, so they could get as hot as 2,000°F (1100 °C). This was more than enough to keep us warm, to provide a heat source for cooking, and to provide a little light for crafts when it was dark outside.

For a million years, 2,000°F was as hot as it got for us, and it was fleeting at best—open fires fluctuate a lot in temperature, and they’re not very reliable for steady, consistent heat. Our ancestors figured out how to smooth this temperature out with coals, but they only provided an approximately steady temperature.

Gradually, then suddenly, the invention of kilns allowed homo sapiens to take a huge leap forward. Ten thousand years ago, after Gö…