dolphins
Explanation
The Joke
Scientists report that they took evidence that dolphins recognize themselves in mirrors, analyzed the subset of dolphins that use tools, and then built up a complete grammar from dolphin vocalizations. They describe how their behavioral analysis slowly built a picture of dolphin intelligence, eventually constructing a full dolphin language. When asked what the dolphins are actually saying, the scientists reveal it is just variations of "ee" sounds. A colleague suggests they could teach dolphins to wear clothes, but then the final panel shows dolphins swimming freely underwater with the observation: "They are more civilized than we gave them credit for" -- implying that dolphins are smart enough to not bother with clothes.
The Humor
The comic plays on the popular fascination with dolphin intelligence and the recurring scientific efforts to prove dolphins are "almost as smart as humans." The buildup creates an expectation that dolphin language will contain some profound insight, but the actual content is just simple squeaking sounds -- deflating the grandiose narrative. The final joke inverts expectations again: instead of humans teaching dolphins to be more "civilized" by wearing clothes, the comic suggests dolphins are actually more civilized precisely because they do not wear clothes. This is a jab at human conventions and the assumption that our cultural norms (like wearing clothing) are signs of advancement rather than arbitrary social constructs. The dolphins, swimming freely, have it figured out better than we do.
References
The comic references real ongoing research into dolphin cognition, including mirror self-recognition tests (which dolphins can pass, placing them in a small group of animals with apparent self-awareness) and observations of dolphins using tools (such as sponges to protect their snouts while foraging).