One could write a lot of good books on when it happened, and how it slipped away. It's the slipping away part that has been rather neglected, I think.
It occurs to me that the fact that History is strongly colored by the chest-beating of the last ape standing may be changing, and the fact that current events (nascent history) are so thoroughly documented in images and from so many points of view may be the birth of a more real history, rather than it's demise.

Peter Linebaugh and Markus Rediker are a couple old geezers who do their part. Along with Zinn.
"A Many-Headed Hydra"

Capitalism searches out the darkest corners of human potential, and mainlines them.