A few days ago I asked this question over in the projects and tech but nobody responded.

"Whilst pondering the timing and cable length limitations associated with the in-frame ACK system, I tried searching for the history of the CAN bus standard and the web just kind of says it was invented as a brand new thing in 1986. Is that the whole story or did it evolve from something else, and was the use of an in-frame ACK system a completely novel idea at the time?"
Does anyone know of any resources that may shed light on its development?