I remember watching this movie some time during the late eighties on VHS from video rental. While it was dubbed in German, I think its original language most likely was either English or Italian (from what I remember regarding the actors as well as the fact that Italian movies were rather popular back then).
Overall style/comedy was very reminiscent of Mel Brooks, it definitely wasn't his History of the World though. I also don't think it was Caveman.
Regarding the actual plot, there's only one specific sub plot/scene that I remember:
There are one or two tribes of cavemen, living in two locations, one being some kind of bamboo house (possibly a treehouse?).
An older member of the tribe has some kind of "accident": Some animal (dinosaur?) eats his whole body and the others are only able to rescue his head. Since everyone has to do his part, they think about his future, then put him on the windowsill to act as an alarm clock for the others.