The location where the Rock Pocket Mouse evolved is the Valley of Fire in New Mexico. It is a sandy place that had kava flows that hardened into 2 types of rock. Black and tan rock. The area spans 40 miles.

The eruption and lava flows happened 1,000 years ago. Though it happened 1,000 years ago the Mice only took 100 years to evolve.

It is a mix of things that was driving the natural selection. It was mainly the fur color of the mice and the environmental changes in the area.

The decrease and increase depend on the specific section of the 40-mile area. It is mainly on the color of rock in that area and there are 2 colors of rock there. If it is tan, the lighter-colored mice survive; for the black rock, the darker color survives.