Actually they have many purposes. The original inspiration for the fibonacci numbers came from 2 rabbits. If you have 2 rabbits, they will breed and you will then have 3 rabbits. 3 rabbits breeds to make 5, 5 to make 8 and so on. The fibonacci sequence. The number of florets on a sunflower spirals out in a fibonacci sequence. There are no doubt countless others too but I'm no historian on the matter.