It's simple to understand that when an animal lives in a certain enviorment it begins to adapt to it. An animal changes colors over time or develops different body protection like hair or fur. Take a Polar bear for a good example. Since they live in a very very cold region they evolved into having fur. The fur itself actually is hollow with air trapped inside. Now air is a bad insulator in general but when it is in a small area where it doesn't move well it is a very good insulator. My question is, is how does evolution "know" these things. I understand how fur could evolve but how could these hollow fur tubes be known by nature.