damn
Explanation
The Joke
A caveman declares: "Damn! All females want to mate with me and Jim! Can make jazz hands longer than anyone!" The scene jumps to "50,000 years later" where a professor explains: "Human males evolved large upper bodies for throwing rocks and spears." Meanwhile, a man in the background is enthusiastically doing jazz hands.
The Humor
The comic satirizes evolutionary psychology explanations for human sexual dimorphism. The standard scientific explanation for why human males evolved larger upper bodies is that it provided advantages in hunting and combat -- throwing rocks and spears. But the comic proposes an absurd alternative: what if males evolved large upper bodies because females were attracted to jazz hands? The caveman who can do the most impressive jazz hands gets all the mates, and over 50,000 years of sexual selection, this produces men with large upper bodies. The joke is that the modern scientist confidently presents the "serious" explanation while a man in the background is still doing jazz hands, suggesting the ridiculous explanation might be the true one. It pokes fun at how evolutionary psychology often constructs plausible-sounding narratives for traits when the real cause could be something far more arbitrary.