"Wherever we've travelled in this great land of ours, we've found that people everywhere are about 90% water"

David Letterman's quote, "Wherever we've taken a trip in this excellent land of ours, we've discovered that individuals everywhere are about 90% water", humorously plays on the typical scientific reality that the body is made up of a significant percentage of water-- typically cited around 60% for adults. Letterman's signature wit is evident as he exaggerates this fact for comedic effect, suggesting that people he encountered across the United States are practically entirely composed of water.

Letterman's hyperbolic statement can be viewed as a light-hearted observation on commonness among varied human populations. In spite of differences in culture, language, and lifestyle, all humans share standard physiological characteristics. The quote metaphorically highlights the concept of unity and interconnectedness amongst people, hinting that beneath the surface diversity, there is a fundamental similarity that unifies them.

Additionally, this quote could be analyzed as a satirical nod to the simplicity with which individuals sometimes search for commonness. By decreasing our shared mankind to a single, exaggerated biological fact, Letterman humorously trivializes the typically complex and nuanced nature of human identity, relationships, and social structures.

In addition, Letterman might be satirizing the sometimes oversimplified narratives presented in media or touristic expedition of cultures. When taking a trip or connecting with various societies, it's simple to reduce rich cultural landscapes to a couple of basic facts or stereotypes. Letterman's quip challenges the audience to acknowledge these propensities while welcoming them to laugh at the absurdity of oversimplification.

In essence, Letterman's quote is a clever combination of clinical reality, humor, and philosophical insight. While concise and apparently trivial, it opens the door to wider reflections on human nature, our shared essence, and the humor that emerges from reconsidering the normal with a fresh, albeit exaggerated, point of view.