Roger Ebert is a national treasure (src):
Evolution involves holding onto your winnings and investing them wisely. You don’t even have to know to how to hold onto your winnings. Evolution does it for you; it is the bank in which useful genetic mutations deposit themselves. There is a very slow rate of return, but it’s compounded. At the end of one eon, you get your bank statement and find your pittance has grown into an orang utan. At the end of the next eon, it has grown into Charles Darwin. Scientists, at least 99.875 percent of them, believe that in the long run only useful mutations deposit in this bank. Those mutations with no use, or a negative effect, squander their savings in a long-running bunko game, and die forgotten in the gutter.