Man's Genesis.

An old man tells his grandchildren about prehistoric man: Caveman Weakhands is unable to court a woman because of his physical weakness. Humiliated by Bruteforce, he bumps into Lillywhite, who has also been cowering in her cave in mourning. The two new lovers form a connection, but Bruteforce separates the couple and sends Weakhands scrambling. In his cave, Weakhands thinks up the design of a stone club. With this equalizer, he soon vanquishes Bruteforce and wins Lillywhite back again-- An early step in human progress.