Someone else can explain it better, but basically the bicameral mind theory posits that the two hemispheres of the human brain only began communicating effectively in recent human history. Based off of symptoms related to illnesses we see now in the modern day, it is believed that this could be a plausible explanation for ancient humans claiming to have spirits, gods, etc talking to them.
That’s one reason I’ve ordered a few titles from PlayAsia recently. For example, the NTSC switch edition of the Metal Gear Solid collection requires downloading the titles. With the PlayAsia edition, lo and behold- everything is on the card, and multiple languages to boot.