Tamari, a byproduct of miso, was the precursor to soy sauce.
It came to ancient Japan from China in the 7th century A.D. The Japanese quickly learned that as they cooked and fermented soybeans to create miso, a pleasantly salty, protein-rich liquid was produced (in fact, “tamari” translates to “puddle” in Japanese). Roughly 1,000 years later, as production became an industrial endeavor rather than a kitchen art, enterprising tamari brewers changed the recipe so it was easier to scale: They brewed a sharper, brinier condiment from a thinner, half-wheat and half-soy mash (faster than waiting for thick, pure miso to ferment), and soy sauce as we know it was born.