I remember the caveman sketches, they began in the very early 70's, and finally peetered out in the late 80's or early 90's.
They usually involved 3 to 4 muppet characters led by their king (usually played by Ernie), who relied on their "Royal Smart Person" (usually played by Sherlock Hemlock) to solve any minute dilema they faced.
While I'm sure there were more, I can only remember 2 or 3 sketches.
1) The cavemen can't find their way out of their cave, & the royal "RSP" invents the exit sign (the sign being effective only if the caveman knew how to read).
2) King Ernie's teeth were dirty, & the "RSP" invents the toothbrush.
3) I can't exactly remember what the sketch was about, but it ended with the cavemen chasing the "RSP" because he hit King Ernie in the hand (or possibly foot) with a rock.