Disgust
Explanation
This comic explores the evolutionary origins of disgust and sexual arousal in the human brain. A scientist explains that sexual arousal involves shutting off the brain's disgust response, which handles reactions to bodily functions like flatulence, mucus, and other biological processes. The humor comes from the escalating awkwardness: the scientist points out that humans have to suppress their disgust reflex just to perform basic biological functions like reproduction, then notes that humans have been "yelling at a concept as if it were some way to undo biology" for years, presumably through prudishness or squeamishness about bodily realities. The final panel has the scientist sarcastically noting that evolution should apologize for this arrangement. The joke is a classic SMBC move of taking a real scientific fact -- that arousal genuinely does suppress the disgust response -- and following its implications to an uncomfortable but logically sound conclusion about human nature.