Evolution
Explanation
The Joke
A person on a dock asks a scientist "What... what are you doing?" as the scientist pushes a large bomb or weapon into the ocean. The title card reads "Evolutionary Biology." The caption at the bottom delivers the punchline: "Proposal: Fill the ocean with weapons to see if anyone evolves hands."
The comic presents an absurd parody of an evolutionary biology experiment. The "researcher" has taken the concept of natural selection -- where environmental pressures drive the evolution of new traits -- to a ludicrous extreme by suggesting that if you put weapons in the ocean, marine creatures will evolve hands to use them. This is, of course, a fundamental misunderstanding of how evolution works.
The Humor
The humor lies in the spectacular misapplication of evolutionary theory. Evolution does not work by placing desired endpoints in the environment and hoping organisms develop specific traits to reach them. The idea that you could force sea creatures to evolve hands by dumping weapons into the ocean is so wrongheaded that it loops back around to being hilarious. The comic is also funny because of the deadpan presentation -- it is framed as a legitimate scientific "proposal," complete with the academic-style caption at the bottom, lending an air of seriousness to an utterly ridiculous idea.
There is also an element of mad-scientist humor: the image of someone casually rolling a bomb off a dock in the name of science captures the SMBC tradition of depicting researchers with zero ethical boundaries and deeply flawed reasoning.
References
The comic parodies the concept of natural selection as described by Charles Darwin. In actual evolutionary biology, environmental pressures do drive adaptation over millions of years, but organisms do not evolve specific traits "on demand" in response to objects placed in their environment. The comic may also be a playful jab at poorly designed scientific experiments or grant proposals that have questionable methodology.