[shakna]

> Soap was likely "invented" and even forgotten over and over again by whoever needed and stopped needing it

At least with the Sapindus family, and probably a few other plants (like lepisanthes) that produce naturally surfactant properties, nature itself provides something akin to "soap", and has been used in bathing for long enough that we're not even sure when it even began.

[culi]

Yup! Sapindus (aka Soapberries) is actually a genus... in the family Sapindaceae... in the order Sapindales. Same etymology as the phytochemical "saponins" which, besides making soap, has a ton of uses and is easy to identify

One very common use of saponin-containing plants is for stupefying fish. Get some fish in a pond, add some saponins, and dinner just floats right up to you. Although saponins are toxic humans have specifically evolved a mechanism to not digest saponins so we can safely eat them (but your dog can't!). Saponins also play a really important role in modern medicine

Saponins are quite common across many unrelated plant species. Ginseng, soapworts, horse chestnut, sapodillas, oleander, soap bark tree, and even spinach are some examples

Because of their myriad uses (as well as their particular taste) and ways to identify saponin-containing plants it's easy to imagine that, regardless of whatever cosmology some culture used to ascribe these properties, most people could easily identify these plants