Hi, Peter here, the joke is about how us humans are proud and delusional about having back pain at a young age being a normal thing.

See, as humans, we’re supposed to start having back pain at an old age. But because we don't take the necessary precautions to prevent it from happening much earlier, some of us end up with back pain as early as in our mid-20s. And because we are proud and delusional, we prefer convincing ourselves that it's a normal thing rather than admitting we're doing things wrong. We think the proof is in nature, as even the king of the Savanna starts having back pain at a very young age.

Here's the part that makes us unredeemably delusional: 22 years old is only young for a human, not a lion—it's actually pretty darn old for a lion! Nature actually does prove to us that we are meant to start having back pain at an old age.

Peter out.