We tend to think of ourselves as the only wholly unique creations in nature, but it is not so.
Uniqueness is so commonplace a property of living things that there is really nothing at all unique about it.
A phenomenon can't be unique and universal at the same time. Even individual free-swimming bacteria can be viewed as unique entities, distinguishable from each other even when they are the progeny of a single clone. Spudich and Koshland have recently reported that motile microorganisms of the same species are like solitary eccentrics in their swimming behavior. When they are searching for food, some tumble in one direction for precisely so many seconds before quitting, while others tumble differently and for different, but characteristic periods of time. If you watch them closely, tethered by their flagellae to the surface of an antibody-coated slide, you can tell them from each other by the way they twirl, as accurately as though they had different names.
--Lewis Thomas, The Medusa and the Snail