Rory has now recovered from a shoulder injury and will take his brother's place on the left wing for the match against the world champions.
The younger of the Lamont brothers, Rory hasn't appeared in national colours since the Calcutta Cup win over England in March when he came off worse in a collision with Iain Balshaw.
Rory's inclusion is the only alteration to Frank Hadden's starting XV, although locks Nathan Hines and James Hamilton both missed Monday's training session with wrist and ankle injuries respectively.
Stade Francais back row Simon Taylor, who was named in the Lions parties of 2001 and 2005, has failed to recover from the calf strain that ruled him out of the defeat to the All Blacks.
Hadden has admitted he was disappointed with the outcome of the game against New Zealand but he believes his side created enough chances to trouble most sides. The former Edinburgh coach feels that, if Scotland can match South Africa physically, then the chance of a victory is very much on the cards.
"We created a lot of opportunities against New Zealand and we're determined to turn them into points this weekend," said Hadden.
"We're expecting a big confrontation and that is reflected in the pack we've gone for. If you don't front up physically against South Africa, you don't get into the game."
Scotland: Chris Paterson; Thom Evans, Ben Cairns, Nick De Luca, Rory Lamont; Phil Godman, Mike Blair (captain); Allan Jacobsen, Ross Ford, Euan Murray, Nathan Hines, James Hamilton, Jason White, John Barclay, Allister Hogg
Replacements: Dougie Hall, Alasdair Dickinson, Matt Mustchin, Scott Gray, Rory Lawson, Dan Parks, Hugo Southwell