Here's everything Wikipedia has to say about this song:
"California Soul" is a pop-soul tune written by Ashford & Simpson, issued originally as a single by American pop quintet The Fifth Dimension in 1969. It was also covered by Motown vocal duo Marvin Gaye and Tammi Terrell that same year and was the duo's last single together when released in early 1970.
Both the Fifth Dimension's version and the Gaye/Terrell version were modest charted hits. The original performed better reaching number twenty-five on the pop singles chart, while Marvin and Tammi's cover reached number fifty-six pop but never charted R&B. The duet was released after Terrell's tragic death from a brain tumor in March of 1970.
The song was a socially conscious-type of song advocating love and peace.
In 1969 Bluenote singer Marlena Shaw also did a version of the song which is now featured in a Dockers commercial circa 2008.
(There's no actual video on this clip. Someone just posted the recording with the song title and artist.)