Before it became Microsoft's Kinect Sports team, Rare was prototyping another way to use the Xbox 360's motion-sensing camera.
Savannah was one of several game prototypes created at the studio after its ownership was transferred from Nintendo.
Savannah's concept was to create a realistic-looking wilderness where players would help raise a lion cub from birth to adult life, ex-Rare staff member Donnchadh Murphy told NotEnoughShaders.
"We knew of the Kinect coming out but we had no real info on how good it was, but the plan was to try and use that technology in Savannah," he explained.
"We really tried to push the technology of the Xbox 360 to get the most out of the graphics. The lions and hyenas were using a custom shell system for the fur, and with the help of a great programmer called Cliff Ramshaw, I think we got some of the nicest looking in-game fur I've seen."
A leaked video of 3D models from the prototype found its way online last year, and included some of Murphy's work.
Like a hybrid of The Lion King and the later also-canned Project Milo, players would need to teach their cub, imbuing it with survival and social skills.
The project was the brainchild of artist Phil Dunne, a veteran of games such as Donkey Kong Country 3 and Killer Instinct 2, now housed at Starfire Studios. Dunne's work never saw the green light, however, like several other Rare projects at the time.
A more realistic-looking Kameo sequel was also canned, as well as a several ideas from Conker's Bad Fur Day creator Chris Seavor.
"At first it seemed that [Microsoft] wouldn't interfere much, but it was soon clear that they were more interested in using Rare to help aim at a younger market. This stifled a lot of creativity, Rare was renowned for their diverse portfolio, so to not be involved in making mature games was a real blow.
"There [were] numerous projects that were put forward that I believe would have been huge hits, but Microsoft rejected them one after the other. I remember seeing a couple of prototypes that Chris Seavor had designed and was working on that looked amazing, but alas they got shelved."
One title that the team were interested in pursuing was Killer Instinct 3. But again, it did not fit Microsoft's vision for the studio, Murphy concluded.
"We all wanted to make Killer Instinct 3, but Microsoft [was] more interested in broadening their demographic than making another fighting game. So it never got made, I doubt it ever will."