Fermented beans, or natto which is eaten by around half of the Japanese, was possibly in ancient diets because bacillus subtitles, the bacteria that ferments beans, is literally found almost everywhere including grass, vegetable surfaces, etc. It’s probably the most common bacteria found in nature.
Im thinking, if wild beans growing in nature fell on the ground, they would ferment due to the presence of bacillus. Is it possible our ancient ancestors picked up these beans and ate them? Many people do like the taste of them, they are the absolute only source of vit k2mk7 and polyglutamic acid
Also if you decide to eat them, speak to a doctor first, they’re potent blood thinners and they dissolve blood clots like no other food
Depends what you mean by ancestral and where you draw the line. Pre agriculture, beans were likely not a common food, as many are toxic when uncooked and they are not easy to gather.