ew-2
Explanation
The Joke
The comic shows a single-celled organism (or early microbe) discovering two other cells in the act of sexual reproduction, exclaiming: "Oh my God, what is happening?! You told me you were just studying together!" The caption below reads: "There must've been a lot of intergenerational tension for the first sexual organism."
The comic imagines the evolutionary transition from asexual to sexual reproduction as a family drama. Prior to sexual reproduction, all organisms reproduced by simply dividing (asexual reproduction). The first organism to reproduce sexually would have been doing something completely unprecedented and, from the perspective of its asexually-reproducing parent, deeply shocking and incomprehensible.
The Humor
The joke works by anthropomorphizing one of the most significant transitions in evolutionary biology -- the origin of sex -- as a sitcom-style "catching your kid doing something scandalous" moment. The parent cell's outrage ("You told me you were just studying together!") is the classic parental line upon discovering their child in a compromising situation. The humor comes from applying this very human social dynamic to single-celled organisms, and from the absurdity of imagining that the literal invention of sex would have been as awkward and mortifying as a teenager getting caught by their parents. The phrase "intergenerational tension" adds an academic understatement to what is depicted as a very dramatic scene.