cranium
Explanation
The Joke
The comic presents three academic-looking figures, each proposing a different scientific hypothesis for why humans evolved larger crania (skulls/brains): the first says it was to make tools, the second says it was to share information while hunting, and the third says it was to acquire mates within complex social groups. These represent real competing hypotheses in paleoanthropology about the evolutionary pressures that drove human brain enlargement.
The final panel, labeled "Two million years ago," shows the actual scene: a proto-human balancing the biggest stick on his forehead while saying to a potential mate, "Me balance biggest stick on forehead. Come. Make babies." This deflates all three serious hypotheses by suggesting the real evolutionary pressure was something far more trivial -- showing off with pointless physical stunts to impress potential mates, essentially the prehistoric equivalent of doing stupid party tricks.
The Humor
The comedy comes from the contrast between the sophisticated academic theories presented in the first three panels and the hilariously crude reality shown in the final panel. Each scientist is drawn increasingly casually (from suit and tie to sweater to casual clothes), suggesting a progression toward less dignified explanations, which culminates in the most undignified answer of all. The joke also satirizes sexual selection theory: while "acquiring mates within complex social groups" sounds intellectual, in practice it might have looked more like showing off pointless feats of dexterity. The alt text ("Feet became less like hands because, for bipedals, it's not useful to give someone the finger with them") extends the evolutionary humor.
References
- Human brain evolution: The comic references genuine debates in evolutionary anthropology about what drove encephalization (the increase in brain size relative to body size) in the hominin lineage. Leading hypotheses include tool use, social cooperation during hunting, and the "social brain hypothesis" proposed by Robin Dunbar.
- Sexual selection: The final panel is a riff on Darwinian sexual selection -- the idea that traits evolve not because they help with survival directly, but because they attract mates, much like the peacock's tail.