# What all unique identifiers does an individual have **URL:** \ **Category:** Factual Questions\ **Created:** [March 5, 2018, 1:01am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034 "2018-03-05T01:01:12Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [March 5, 2018, 1:01am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/1 "2018-03-05T01:01:12Z")
I know fingerprints and DNA are unique to each individual (unless they are identical twins, then DNA is identical). What other physical attributes are totally unique to each individual? I assume facial recognition technology is advanced enough that it can distinguish one person from the other 7 billion. The veins on the back of people’s hands can be used to ID someone. Teeth and dental records Eyes are unique to everyone. I looked online and saw this article which had a lot of interesting info I didn’t know. > **[The other 'fingerprints' you don't know about | CNN](https://www.cnn.com/2015/12/04/health/unique-body-parts/index.html)** > > Move over fingerprints. From your ears to your toes, there are many body parts that make you uniquely special and identifable from others in a crowd. in addition to some of the items I listed above, everyone’s ears, tongue, gait, voice are unique. Apparently both the retina and iris are unique to everyone, so 2 ways the eye is different for everyone. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 5, 2018, 1:12am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/2 "2018-03-05T01:12:44Z")
Some of these aren’t actually unique enough to pick out one individual out of 7 billion-- When they’re used, the pool is already narrowed down considerably in some other way (like a particular city). Bone marrow type isn’t completely unique, either, but there’s still room for an awful lot of variation. And it’s kind of an obvious extension from fingerprints, but there are also toeprints. They’re used more often for babies, for some reason I can’t remember. ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [March 5, 2018, 2:23am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/3 "2018-03-05T02:23:25Z")
> [@](#): > > And it’s kind of an obvious extension from fingerprints, but there are also toeprints. They’re used more often for babies, for some reason I can’t remember. > [@](#): > > “Maybe. But on Riff they take identity on a baby before he leaves the delivery room.” "My people, too. But — " “Sure, sure! It’s common practice. But how?” Brisby looked blank, then banged the desk. “Footprints! And we didn’t send them in.” Heinlein doesn’t answer your question, but suggests that at least in the galactic future, this is standard. My birth record has footprints. WAG that we wear off the friction ridges by walking. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [March 5, 2018, 8:24am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/4 "2018-03-05T08:24:09Z")
It seems to me that fingerprints are described using numerical descriptions of their finite number of features. Has there ever been an instance in which the fingerprint description of one person has been found to be the same as another, given that an analysis of the two prints would reveal discernible differences too small to quantify in the numerical code? ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [March 5, 2018, 9:09am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/5 "2018-03-05T09:09:56Z")
> [@jtur88](#): > > It seems to me that fingerprints are described using numerical descriptions of their finite number of features. Has there ever been an instance in which the fingerprint description of one person has been found to be the same as another, given that an analysis of the two prints would reveal discernible differences too small to quantify in the numerical code? There was one case some years back, and new Research just recently, that pointed out that while theoretically, DNA and Fingerprints might all be unique, in practice, only parts of each are examined, and there’s much more overlap than previously thought. In case of DNA, only about 20 markers or so are compared, which led to one Canadian being arrested as Terrorist for an attack in Europe, until he could prove he was physically thousands of miles away on that day when parts of DNA were found at the site. As Fingerprints, a recent study showed that the whorls actually looked at are very similar among Close relatives. ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [March 6, 2018, 3:30pm UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/6 "2018-03-06T15:30:54Z")
I think you have to define unique. Literally unique-no duplicates anywhere anytime, would be extraordinarily hard to come up with and impossible to prove. Practically unique-many traits. But to get an answer, you have to define what you mean. 1 person on the planet at any given time? 1 person in 50,000? (Apple fingerprint scanner) 1 in 300 million? (DNA from what I have read). Also, you probably should look at how easy it is to fake. Just because a fingerprint scanner can correctly identify a person doesn’t mean it isn’t easy to fool. You might check out what the FBI is doing in this regard: > **[Welcome to fbi.gov | Federal Bureau of Investigation](https://www.fbi.gov/?came_from=https%3A%2F%2Fwww.fbi.gov%2Fservices%2Fcjis%2Ffingerprints-and-other-biometrics)** They constantly study the issue and are on the lookout for new methods and techniques. ---
**Author:** ![Oly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/oly/32/8255_2.png) [@Oly](https://boards.straightdope.com/u/Oly)\ **Post date:** [March 8, 2018, 5:08am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/7 "2018-03-08T05:08:34Z")
Skeletal xrays have unique features. The frontal sinuses of the skull are easily discernible as different from person to person. Then just the contours of the bones, when looked at by an experienced examiner have enough individual features to make an ID. It’s important to keep in mind though that for any of thses things to work you have to have a reference sample to compare. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [March 8, 2018, 6:26am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/8 "2018-03-08T06:26:59Z")
> [@constanze](#): > > There was one case some years back, and new Research just recently, that pointed out that while theoretically, DNA and Fingerprints might all be unique, in practice, only parts of each are examined, and there’s much more overlap than previously thought. This may be true for fingerprints, I don’t know, but we understand human genetic variation extremely well. So far as I’m aware, it’s not true that there is “more overlap than previously thought” for any of the markers in common use - do you have a cite for this claim? DNA test results always include probabilities, and more markers can be typed if greater certainty is needed. > [@constanze](#): > > In case of DNA, only about 20 markers or so are compared, which led to one Canadian being arrested as Terrorist for an attack in Europe, until he could prove he was physically thousands of miles away on that day when parts of DNA were found at the site. I’ve never heard of this case, can you give a link? I can’t find it by googling. ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [March 8, 2018, 9:46am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/9 "2018-03-08T09:46:56Z")
> [@Riemann](#): > > This may be true for fingerprints, I don’t know, but we understand human genetic variation extremely well. So far as I’m aware, it’s not true that there is “more overlap than previously thought” for any of the markers in common use - do you have a cite for this claim? DNA test results always include probabilities, and more markers can be typed if greater certainty is needed. DNA test results for paternity may include probabilities, but the first problem is that there are different methods to get a DNA “fingerprint”, which have varying degrees of how exact they are vs. how quicky they are vs. how much they cost, which influence law enforcement; in addition to different countries choosing different methods; in addition to methods changing over time. Here’s an article [http://www.fsigenetics.com/article/S1872-4973(09)00099-4/abstract](http://www.fsigenetics.com/article/S1872-4973%2809%2900099-4/abstract) where forensic scientists talk about how easy DNA can be faked. Here is a short article [Forensic Bioinformatics - DNA Testing Issues](http://www.bioforensics.com/dna-testing-issues/) of problems. One problem not directly related to DNA was methodology error in case of the Phantom of Heilbronn [Phantom of Heilbronn - Wikipedia](https://en.wikipedia.org/wiki/Phantom_of_Heilbronn) where the cotton swabs used to take samples were contaminated. Another problem that has only recently come to light because of the increase in amount of DNA tests: how many chimeras [Chimera (genetics) - Wikipedia](https://en.wikipedia.org/wiki/Chimera_(genetics)) exist not only in Dr. House episode, but in real life. One of the problems that contributed to the false terrorist case was that only a partial amount was recovered from the scene, further limiting how unique the result was. > [@](#): > > I’ve never heard of this case, can you give a link? I can’t find it by googling. It seems I misremembered this: it was normal fingerprints, not DNA: [Brandon Mayfield - Wikipedia](https://en.wikipedia.org/wiki/Brandon_Mayfield) > [@](#): > > The FBI described the fingerprint match as “100% verified”. … > As was discovered during the court case, even the FBI’s own records show that this fingerprint, despite the sworn testimony of FBI and DOJ agents, was in all reality not an exact match but only one of 20 prints “similar” to the ones retrieved from Madrid. Based on that list of people with “similar prints” … Here’s [https://webfiles.uci.edu/scole/Publications/MoreThan0.pdf](https://webfiles.uci.edu/scole/Publications/MoreThan0.pdf) a PDF article in a journal about the problems with fingerprints as currently used by law enforcement. Here’s an article [Forensic science 'too unreliable', says report | New Scientist](https://www.newscientist.com/article/dn16631-forensic-science-too-unreliable-says-report) about lack of scientific data for the theory underneath. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [March 8, 2018, 12:41pm UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/10 "2018-03-08T12:41:36Z")
> [@constanze](#): > > DNA test… You have linked to a selection of articles about various other issues such as sample contamination. None of them support your claim that there is “more overlap than previous thought” for the markers commonly used in DNA fingerprinting. And how would Chimerism lead to a false positive, even if its prevalence were significant? Surely it could only potentially lead to a false negative. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 8, 2018, 1:35pm UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/11 "2018-03-08T13:35:30Z")
Besides, with DNA, there’s always the option to do a full sequence, if some limited set of markers is inconclusive. It’s still too expensive to do for _every_ case, but it can be done if needed. ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [March 9, 2018, 9:49am UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/12 "2018-03-09T09:49:19Z")
> [@Chronos](#): > > Besides, with DNA, there’s always the option to do a full sequence, if some limited set of markers is inconclusive. It’s still too expensive to do for _every_ case, but it can be done if needed. Is the accused entitled to demand a full (expensive and lenghty) DNA sequence if they believe / know that the quick DNA match is wrong? Or would they have to pay privately and then try to introduce it as additional evidence during Trial? ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [March 9, 2018, 2:50pm UTC](https://boards.straightdope.com/t/what-all-unique-identifiers-does-an-individual-have/810034/13 "2018-03-09T14:50:47Z")
[Lip prints](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3722715/)