I remember doing a question like this in class while learning about natural selection. The 2 colorations of moth live in a habitat that originally supported the lighter variant due to the light-colored trees. When the industrial revolution began, the soot levels reversed this because the black moths were more camouflaged that the lighter ones. A way we could prove this was the amount of black dresses and dark colored clothing during the time, often due to the fact that lighter colored clothing would turn black by the time the wearer arrived home. The lighter colored moths simply died off a bit because of this.
