Praise then darkness, and creation unfinished

My employer has what we cheerfully refer to as the "science art library," meaning illustrations that they've had drawn for some past science book and can reuse: a trilobite, a triple beam balance, some graduated cylinders and thermometers, food chains, and an assortment of graph: a circle graph of where the planet's fresh water is, curves showing radioactive decay, some notional illustrations of things like ages of pine trees in different forests or the death rate of fish in a pond that is being over-fertilized. I was looking for a graph to use today for a practice question, where the point was graph reading rather than the specific content. Skimming through the library, I came across a line graph. Neat, boring, straight line rising from lower left to upper right, no units or other numbers.

The x axis is labeled "latitude."

The y axis is labeled "rabbits per liter."

My coworker and I were unable to come up with any explanation for what this might mean, or where it came from.

It has been brought to our attention that we've come to take certain oddities for granted. To wit: we've been so bombarded by the Santa Claus story and the stockings hung on the chimney with care, that we've only recently stopped to wonder how in the world people started hanging socks on their walls. —from the Powell's Books newsletter