Everybody agrees he took on an important question, but his answer was not right. I spoke to a Greek classics scholar who said Jaynes's interpretations of the evolution of Greek emotion names was very far off the mark.
The most fundamental problem is that the dates don't line up. Causes and effects are separated by millennia.
It remains a mystery.
A bigger mystery is where the pre-dynastic Egyptians got hold of all those extremely precisely worked, very, very hard stone bowls and jugs. Some are of carborundum! All we know is that they were completely unable to make them themselves. We would be hard-pressed to make those today, using our most advanced fabrication tools.
Likewise the 50+-ton basalt boxes found empty underground at Saqqara, polished to a mirror sheen, optically flat, with interior faces exactly parallel.