One Million Years B.C. (1966)

Tumak, a member of the Rock Tribe, is expelled from their cave after running
afoul of their leader Akhoba, who also happens to be his father. After several
days of wandering, he meets stumbles upon several female members of the Shell
Tribe, a group that lives on the coast. Loana, the daughter of the chief, sees
that he is in terrible shape from his ordeal and nurses him back to health. This
causes her betrothed to become jealous and eventually the two of them get into
a major fight and Tumak is expelled as a result. However, Loana decides to join
him and follows him back to the caves of his people. While there Loana teaches
the Rock people civility and this causes Tumak to become the new leader This
doesn't sit well with Tumak's brother Sakana who begins to plot to have Tumak
overthrown. (IMDB)