Fingerprints have long been used to identify people, but they can be faked by creating copies. Similarly, the pattern of the iris in the human eye is a reliable source for ID—until someone alters the pattern with a contact lens to skew the results. The use of biometrics to identify individuals can be defeated. So, what qualifies as a unique identifying characteristic? It turns out that everyone’s blood-vessel patterns are unique and virtually impossible to counterfeit. Your own personal “vein map” is a one-of-a-kind identifier, setting you apart from everyone else on the planet.

Pondering such complexities of human beings should…