symmetry-2
Explanation
The comic shows a woman being evaluated by two aliens. One alien critiques her appearance, saying her teeth are too big, she has weird spots, and she's not bilaterally symmetrical enough. The other alien tells the computer to "throw it back." The caption reads: "Sally fails to be selected as a holotype human."
A holotype is a single physical specimen of an organism that serves as the definitive reference for its entire species in biological taxonomy. The joke reverses the usual dynamic of humans studying and classifying animals. Here, aliens are trying to pick a representative specimen of the human species, and they reject Sally because she doesn't meet their standards of what a "typical" human should look like. The humor lies in applying the cold, clinical language of biological classification to a person, and in the absurdity that any individual could perfectly represent an entire species. It also plays on the idea that the criteria for being a "good specimen" are hilariously superficial -- teeth, spots, and symmetry.