Firstly, ALL alleles were once rare. Thats how molecular evolution works. The important thing to remember is that the fuel for evolution is diversity. My point is that it makes no sence to look at evolution that way.
Evolution is a big fluke.
Just 'cause it would be nice to have a fur coat doesn't mean you will develope one. All the best. On taking it out of my net and opening the glorious wing, my heart began to beat violently, the blood rushed to my head, and I felt much more like fainting than I have done when in apprehension of immediate death.