I must say this is the most beautifully phrased identity mapping I have seen
Your DNA is you. You are your DNA. It is not assigned to you nor can you change it. It is your identity. Everything else is simply a "handle", a shortcut or nickname for the identity that is you.
Scott presents valid arguments against this perspective saying DNA is not 100% unique (fraternal twins and cloning) but his second argument that DNA does not mean anything in jungles of New zealand does not sound appealing to me. I mean whatever means of identity (token, certificate ...) you come up with, there will be a part of world which would not recognize it.
DNA coupled with hand prints (which are different for even fraternal twins) makes an interesting case.
Another important thing to see in his phrase is notion of "handle". I think every thing comes down to the fact that how secure, portable and efficient your handle is. Hey, am I saying Smartcards are the best handles :)
The phrase above is invention of Dave Kearns . I am a big fan of newsletter on identity management by Dave.