Actually, there's some evidence as to how ancient Americans discovered nixtamalization. Among pre-agricultural societies across the world, a common method of boiling water before the invention of earthenware was to dig a hole with the water, put a rock in a nearby fire, and drop the heated rock, called a pot boiler, into the water. What they discovered is that if you used limestone, which is common across the Americas, as a pot boiler, the resulting reaction between the heated limestone and water made limewater, providing the necessary alkaline environment for nixtamalization.
Actually, there's some evidence as to how ancient Americans discovered nixtamalization. Among pre-agricultural societies across the world, a common method of boiling water before the invention of earthenware was to dig a hole with the water, put a rock in a nearby fire, and drop the heated rock, called a pot boiler, into the water. What they discovered is that if you used limestone, which is common across the Americas, as a pot boiler, the resulting reaction between the heated limestone and water made limewater, providing the necessary alkaline environment for nixtamalization.