From the Super Mario Wiki
The Cave People are native humans of Dinosaur Land who have appeared in many episodes of the Super Mario World animated series. The Cave People are generally rather short and stubby in appearance, often having long hair. The only notable Cave Person is Oogtar, who replaces Toad from The Super Mario Bros. Super Show! and The Adventures of Super Mario Bros. 3 (though Oogtar's voice actor is the same one who voiced Toad). Cave People appear to be somewhat unintelligent in comparison to present-day humans. Cave People resemble and are likely based on the prehistoric peoples of Earth.
In The Super Mario Bros. Super Show! episode "Quest for Pizza", Caveman Land was apparently home to humans akin to Cave People. However, only one person named Mugga was ever seen. The rest were all shown to be Cave Mushrooms, and were essentially primitive Mushroom People.
Mario has also encountered similar people in the Club Nintendo Super Mario: Verloren in der Zeit who also bare an uncanny resemblance to the Cave People from the Super Mario World animated series, such as Joe & Mac.