Survival in ancient times wasn't easy. Even today, food spoilage is an issue, but back then it was absolutely critical to make the most of any food that was hunted, gathered, or grown. If a family's food spoiled, they might end up starving until the next harvest or hunt.

This dilemma led to the development of basic food preservation methods. Meat was salted or smoked, vegetables were pickled or fermented, and fruits were dried or turned into jam. However, in order to preserve produce in its fresh state, refrigeration was needed. Electricity was obviously not an option, so ancient societies turned to evaporative cooling, the same principle that allows sweat to cool our bodies. As dry air passes around a wet object, the evaporation of that moisture creates a cooling effect.

As far back as 2500 B.C., Egyptians recorded the use of a device called a zeer pot. This primitive evaporative cooler is constructed of the following components:

• Large porous clay pot
• Smaller clay pot (may be glazed to prevent moisture from seeping in)
• Sand
• A cloth to cover the pots
• Water

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The small pot is placed inside the large pot, sand is used to fill the space between the two, and water is used to soak the sand and cover cloth. As water seeps through the porous outer pot, warm, dry air causes it to evaporate continuously, drawing heat out of the sand and innermost pot. This can be used to keep vegetables, fruit, or drinking water cool in arid regions. The zeer pot is still used to this day in third-world countries where access to electricity is limited.

The following video from YouTuber CrypticCricket shows the effectiveness of a zeer pot cooler, even in the high humidity of Florida. Hotter and drier climates with strong breezes will increase the pot's evaporative cooling effectiveness.

Written by Patrick McCarthy