From the sound of it, neither actor really enjoyed being a caveman thanks to feathery wigs that just never stay out of your lunch (welcome to the fun of long hair, boys!), and the close encounters with bodily excrement. When asked what time period they'd like to return to, both opted for eras of a little more refinement:
If you guys could live during any time throughout the course of history, when would it be?
Black: My favorite time in history ... the Renaissance.
Cera: I would say ... the '30s. The 1930s.
Black: The '30s? Wait, isn't that the Depression?
Cera: Like '33, that was a great age.
Black: Come on, the Renaissance! Haven't you ever been to the Renaissance fair? Don't you wish that was real life? A little mead, a little roast ...
That knowledge undoes everything girls have been taught about men! I mean, for years girls have labored under the delusion that you wanted to return to the simpler days of hunting with spears, and cooking by fire. If you prefer civilization then please, start up some petitions or websites or something to set the record straighter ...