This is indeed an excellent bass line, totally buried in the mix, which is really too bad as it's very Motown in every detail.
It should have been better mixed, the way they were doing it at Motown, but British ears at the time were not accustomed to this kind of vibe, and so was the B team at Atlantic records, even if it's been recorded in Memphis by some of the Aretha Franklin's usual suspects...
Here it is, if you want to learn it. 😉