Although this little drama of primitive man was apparently intended as a serious work, it's awfully difficult to watch it today without at least cracking a smile.  Whatever the filmmakers' intentions—and they're not entirely clear—Man's Genesis is undeniably funny.  Perhaps director D.W. Griffith was concerned that audiences would find this material amusing no matter how he handled it, for he added a subtitle calling the film "A Psychological Comedy (whatever that is) Founded Upon the Darwinian Theory of the Evolution of Man."  Looks like he was hedging his bets:  if they laugh, fine, it's a comedy.  Otherwise, the film seems intended as drama, taking the audience back to the discovery of creative intelligence; specifically, to the very moment a primitive man discovers his ability to craft a tool—specifically, a weapon—to achieve an important goal.  This isn't at all the "genesis" of humanity, but why quibble?

Despite having to wear grassy outfits that are sure to provoke mirth, the actors appear to take their roles seriously, especially the leading lady, solemn-faced Mae Marsh, and they emerge with dignity more or less intact.  The structure of this film is problematic, however.  The story is related as a tale-within-a-tale, told by an old man to a pair of siblings, a little boy and girl who are fighting.  Apparently, the old man's intention (and the director's?) is to indicate that we should use our intelligence to solve conflicts, that Might does not make Right, but the protagonist of his story uses his intelligence to build a club, and pound his enemy to death.  Hasn't he proven that Might, backed by intelligence, is indeed Right?  At the end, when the old man finishes telling this story, we half expect the little boy to put the lesson to use by building a club to pummel his sister; instead, the kids go off together happily, hand-in-hand, having learned...What, exactly?

Man's Genesis is not entirely ridiculous.  It's well worth seeing, either for campy laughs or to get some sense of what contemporary attitudes were about early civilization, but no one is going to mistake it for a serious work of speculative anthropology, either.