Cheeseburgers, Proof of a High Level Civilization

Why you couldn't have a cheeseburger before the modern era:

Tomatoes are in season in the late summer. Lettuce is in season in in the fall. Mammals are slaughtered in early winter. The process of making such a burger would take nearly a year, and would inherently involve omitting some core cheeseburger ingredients. It would be wildly expensive-requiring a trio of cows-and demand many acres of land. There's just no sense in it.

A cheeseburger cannot exist outside of a highly developed, post-agrarian society. It requires a complex interaction between a handful of vendors-in all likelihood, a couple of dozen-and the ability to ship ingredients vast distances while keeping them fresh.

A lot of things are like this.  I spent Monday on the grounds of a very large coal-fired power plant. A lot of people have no clue what happens because they flip a switch to turn on the light.