The first and most enduring explanation for what causes tooth decay was the tooth worm, first noted by the Sumerians around 5000 BC. The hypothesis was that tooth decay was the result of a tooth worm boring into and decimating the teeth. This is logical, as the holes created by cavities are somewhat similar to those bored by worms into wood.
The ivory sculptures below depict the havoc wrought by these wicked worms.
The idea of the tooth worm has been found in the writings of the ancient Greek philosophers and poets, as well as those of the ancient Indian, Japanense, Egyptian, and Chinese cultures. It endured as late as the 1300s, when French surgeon Guy de Chauliac promoted it as the cause of tooth decay.