Brachos 58- ברכות נח

We learn that a bracha is said upon seeing a multitude (600,000) since it contains the full spectrum of minds which equal that number, and is reflected by their dissimilarities in facial features as well.  Since there certainly exist more than 6000,000 people in the world, this apparently denotes that there are duplicates as well, if so why don’t two people ever look alike?