A report from The Economist on the use of biometrics in security systems concludes with the line
And everyone would be better served if a good deal more was known about what it is, biologically, that makes each and everyone of us a unique human being.
This, after the report outlines how biometric systems can and have shown how biometrics such as fingerprints and even our very DNA (separate source) have been shown to not be as unique as we once believed. The final question, then, comes from operating on naturalistic assumptions that humans are merely the sum total of their physical components.
It’s only too bad that so many in our society have abandoned the classic notion that humans in particular are not merely complex machines. The concept of a soul is seen as foreign to so many in our culture. There is, however, mounting evidence that points towards the uniqueness of men as originating from somewhere other than the physical atoms that make up our bodies.
For an excellent treatment of this subject, I highly recommend philosopher JP Moreland‘s excellent work on the subject, here is a paper titled “Naturalism and the crisis of the soul”. Here is another overview of the subject by Greg Koukl titled “All mind, no brain”.