What seems to have changed in our psyches was a great catastrophic event--probably related to climate change--that decimated our ranks about 135,000 years ago. At that time, the entire population of the subspecies that we now call human plummeted to just six hundred.
Man that is a crazy scary number!
The creative adult is the child who has survived.
Le Guin resents the misattribution and considers the sentiment vapid, which kind of bums me out because I like it, for sometimes all too obvious reasons.