"The River of No Return" from Anthro #5 (DC, 1969) by Howie Post
You know what I miss? A good caveman comic on the stands. I'm not being facetious, I'm fascinated by this minor genre, probably because I grew up on French-language Rahan comics. Still don't believe me? Let it be known that I've run GURPS: Ice Age role-playing games. And they were COOL.
Anthro is the first Cro-Magnon boy born in the Stone Age, and maybe(?) the first comic book caveman hero. So he's smarter than his Neanderthal tribe and I guess he's expected to have lots of babies and found the human race. No pressure.