Sly was years after 'Out of sight'. And I know you know Alvin Robinson's recordings which were before that. And the Mar-Keys were the beginning. The whole of Stax would have been zilch without them.
Funk, to a large extent, represented the resurgence of jazz in popular black music and the vocalists contributed little to that (except to the extent that they - like JB and a few others - were musicians too).
MG
A lot of people had an influence on what came to be called funk. You could bring up Horace Silver, Bobby Timmons, and Cannonball as influences.
I still think that the rural quality of Otis' music wasn't something found in most funk. I would agree with you that Al Jackson, Jr. had an influence on funk.
This an argument that could go on and on and never be resolved. I agree with much of what you say.
As far as this thread goes, both of us have outlived Otis, Al Jackson, Jr., Bobby Timmons, and Cannonball - for whatever that's worth.