Considering what is speculated about ancient cultures and their diverse impetuses...impeti?...well, how about influences...where do the geometric designs of Egyptian tombs and temples arise from?
Such colour and extrapolation and obvious simple constructs that interact with themselves to become so much more in just the one design...was Gretal May-Believe responsible for combining colours and forms into one offering because she was the best of her ilk? Or, portray, an influence made some folk take what they 'saw' in their mind to something they could be portrayed upon a surface?
Does a normal mind create interacting colours and forms that are not normally found in nature?
Check out some of M C Escher's work, and add some colour to it. And wonder how folk 5,000 years before were doing similar.
Mushrooms as an influence? Too easy...so too other substances such as a by-product from mouldy grains and bread. And then there is Afghanistan not too far away, and the lotus flower right there...all depends on how things are processed and taken into the body...
...care to take another look at the Eye of Horus and a mushroom surrounded by a couple of other parts?
But maybe these things are open to interpretation. I wonder...who first experienced the effects of a mushroom, and told someone else, and where it is recorded in writing?
If the written words are all we should go by, we are stuffed because the Library of Alexandria was destroyed twice, and it housed all the ancient knowledge that none can avail themselves of now...
I guess those who ask for evidence in writing are not quite good enough to say those who offer evidence without writing might do better.
Bugger...is this one of those pictures that folk need to see? A picture of a thousand words? With lots of colours? Here's a chess board for other kinds of folk...simple pattern; two colours...and nothing to see here.