The term "caveman" is most closely associated with the Neanderthal peoples. However, in reality the Neanderthals and the Cro-Magnon peoples were basically nomadic and migrated along with the fauna which they hunted.
With this in mind, the concept of "caveman" here could also include the various peoples who existed before and after the arrival of Homo sapiens such as Australopithecus afarensis, Homo erectus, Homo sapiens Neanderthalensis, etc.
It could also be extended to include Homo sapiens sapiens throughout the "Stone Age" up to the Chalcolithic Period (also known as the "Copper-Stone Age") which began approximately 5,000 BC along with the transition from migration to settled farming.
Regardless of scientific fact, in popular fiction (including superhero fiction for most of its publishing history), cavemen have been depicted as quasi-simian ancestors of humanity of superhuman strength (such as DC's Evolvo Lad when he is in his "caveman" form). Most often, these fictional cavemen co-exist with prehistoric reptiles and dinosaurs from a smorgasbord of eras; in most such stories, the "rule of cool" and adventure tropes cheerfully take precedence over scientific facts and prehistoric reality. In modern times, this is sometimes rationalized through the "lost world" trope, a trope based upon creatures from vastly different eras somehow living together in a "land that time forgot" (such as DC's Skartaris or Marvel's Savage Land).