Like snowflakes, every person's saliva is unique, a fact which may hold the key to everything from easily accessed medical histories to super-secure computers.
Biometrics has been trying to discover for years what makes us unique. Fingerprints and retinal scans have become the standards for most biometrics, but they still have massive drawbacks, as many heist games and movies illustrate.
However, a new worldwide survey of the human saliva microbiome - the bugs in our spit - finds that a man from England shares no more microbes in common with his neighbors than with a woman from Africa.
The survey, which was conducted by Mark Stoneking, a molecular anthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, could have far-reaching implications.
Both fingerprints and retinal scans fail in picking up genetic traits within their biometrics, which make them only useful for tracking an individual; stomach ulcer bacteria do contain these traits and have been used to date human migration, but require a stomach biopsy.
Genetic traits hidden within your identification can be used for a number of purposes. Apart from determining your identification accurately, it can also hold genetic information like diseases, parentage, children, age, allergies.
The beauty of the spit method is that it's simple to get hold of, but can contain genetic traces that could allow detailing not just the individual, but the whole family line. An ambulance man with a "spit-ID" could run a quick swab test and with some accuracy automatically find out who you are, who to contact and what medicines to give and not to give you.
It could even lead to heightened computer security. Forget passwords and user names - just dab a bit of saliva on a pad and you're good to go. Having a "spit-lock" as part of your computer logon does seem a little gross, though.