Originally Posted by Driven

There's no 'wild guesses' involved. Gilmour has said several times that he played a large amount of the bass parts, because it was quicker to do it that way (I think someone else posted the name of the particular article). Gilmour also said Waters was given 'bass player' awards for parts that were actually played by David, and Roger would say "thanks Dave"!!

You're not going to get photographic evidence (unless you can carbon date negatives to that day they were in the studio)...but the fact that Gilmour has said it, and Roger hasn't disagreed suggests it's the truth.

As to the question of "how did Roger play those parts live"...the short answer is he didn't. Bootlegs of the animals tour show the bass lines were far less complicated than the original recording...and they also had a second bass player for fretless parts etc.