mona-lisa
Explanation
The Joke
The comic features a character (likely meant to be an alien or future being) viewing the Mona Lisa and discussing human art. The character notes that humans are "an interesting species" and that they "paint loads of 'em" -- referring to portraits. They observe that there is a particular fascination with painting attractive human forms, but there is also the darker side: "Some of those people are four hundred years old and some of them wanted to be blurred from it and pain."
The discussion turns to a more pointed observation about demographics: "I never thought demographics could equal demographics problems." The final punchline delivers the darkest twist: "Also, some people deserve to die, and we could use them to save paintings" -- suggesting using undesirable people as raw material for art preservation. The caption reads something like "Sure, come offer my portfolio."
The Humor
The humor comes from the escalating absurdity of an outsider's perspective on human art and culture. What begins as an innocuous anthropological observation about portraiture quickly spirals into increasingly uncomfortable territory. The comic plays on the trope of an alien or outside observer misunderstanding human customs and arriving at horrifyingly logical but morally monstrous conclusions. Each panel pushes the reasoning one step further into darkness, culminating in a casually stated monstrous suggestion delivered with the same detached analytical tone as the opening observation. It is classic SMBC dark humor -- taking a premise to its most extreme logical conclusion.