thank-you
Explanation
The Joke
A man is shown praying with his eyes closed and hands clasped. But instead of thanking God for the usual blessings, he says: "Thank you for a relatively long lifespan, for alcohol dehydrogenase, and above all, for internal fertilization." The caption below reads: "It's too bad we don't worship Evolution."
The Humor
The comic imagines what a prayer of gratitude would look like if it were directed at evolution rather than a deity. Instead of thanking God for abstract blessings like love, family, or purpose, the man thanks evolution for specific biological adaptations: a relatively long lifespan (compared to many other species), alcohol dehydrogenase (the enzyme that allows humans to metabolize alcohol without dying, enabling us to enjoy drinking), and internal fertilization (as opposed to, say, spawning eggs into water like fish). The humor comes from the absurd specificity and the uncomfortable biological honesty -- these are genuinely things that make human life enjoyable, but they sound hilariously clinical and undignified when listed as blessings. The joke also implicitly pokes fun at the arbitrariness of what people choose to be thankful for in traditional prayers.
References
Alcohol dehydrogenase is a family of enzymes that break down alcohol (ethanol) in the body, primarily in the liver. Without it, even small amounts of alcohol would be toxic. Internal fertilization is the reproductive strategy used by mammals, birds, and reptiles, as opposed to external fertilization used by many fish and amphibians.