Located on the tips of our fingers are features known as friction ridges. We evolved them to get a better grip on objects.
It just so happens that those friction ridges are unique to every person.
That allows us to use friction ridges as unique identifiers and for authorities to use them to catch criminals, and in some ways, we have been doing so for centuries.
Learn more about fingerprints and fingerprinting on this episode of Everything Everywhere Daily.
Fingerprints are something that has been with us long before we became human.
While we don’t have fossilized fingerprints from early humans, we do know that closely related animals, such as gorillas and chimpanzees, also have fingerprints.
Fingerprints, or friction ridges, are believed to have evolved for several reasons. The biggest reason is that increasing the surface area on our fingers, even ever so slightly, makes it easier to grip and hold objects. Additionally, the ridges on our fingertips allowed us to detect more subtle textures and variations in the surfaces we were touching, providing us with better tactile sensitivity.
Fingerprints begin to form as early as the 15th week of pregnancy and remain with us until we die.
While fingerprints are unique, they are not totally random. There are genetic trends that can make fingerprints for related people similar. Identical twins will not have identical fingerprints, but they will have similarities. Fraternal twins may have fingerprints that are not quite as similar.
The reason why fingerprints are unique is that they aren’t solely determined by genetics. It seems that even small environmental factors in the womb, such as pressure and position of the fetus, can cause fingerprints to develop differently.
The knowledge that fingerprints were unique goes back at least two thousand years. We know that impressions of thumbs were used on clay tablets as identification in ancient Babylon as early as 200 BC.
Unintended fingerprint evidence has been found in clay pottery and paintings in the Indus Valley, Greece, and ancient Egypt. In fact, some evidence of fingerprints has been found in cave paintings that date back 10,000 to 15,000 years.
When paper developed in ancient China, an entire handprint would sometimes be used to authenticate documents.
While it didn’t have the same sophistication of modern techniques, the Babylonian king Hammurabi took the imprints of criminals in the 18th century BC. When possible, hand and footprints were taken from crime scenes during the Qin Dynasty in China.
We have documentation from the Chinese historian Kia Kung-Yen in 650 that fingerprints could be used as identification. The 13th-century Islamic scholar Rashid-al-Din Hamadani commented on the Chinese practice of using fingerprints by noting that “Experience shows that no two individuals have fingers exactly alike.”
The use of fingerprints goes back much earlier than most people realize.
However, these first uses of fingerprints were pretty crude.
A more systematic understanding of fingerprints began in the 17th century in Europe. They had the benefit of using modern inventions such as magnifying glasses to get a closer look at fingerprints.
In 1686, the Italian anatomist Marcello Malpighi was the first to identify the major components of fingerprints, including loops and ridges.
In 1788, the German anatomist Johann Christoph Andreas Mayer rediscovered what the Chinese knew centuries beforehand, that fingerprints were unique.
The modern use of fingerprints can be said to date back to the 1880s.
It started in 1880 when a Scottish doctor working in Tokyo named Henry Faulds published a paper on identifying people with fingerprints and a possible way to record them using printer ink.
Faulds actually managed to solve a crime in his hospital by using fingerprints. He also conducted an experiment where he filed off his fingerprints to see if they would grow back.
In 1886 he returned to Britain and offered his system to the Metropolitan Police, who declined the offer.
However, in 1892, Francis Galton, a guy who had a lot of other crazy ideas which were later debunked, published his book “Finger Prints.” In it, he estimated that the odds of two fingerprints matching were 1 in 64 billion.
That same year in Argentina, a woman by the name of Francisca Rojas was found beaten in her home, and her two sons were murdered. She accused her neighbor, but a bloody thumbprint left at the murder scene pointed to her, and she later confessed.
This was the first murder case ever solved with the use of fingerprints.
Galton’s book got the attention of Sir Edward Henry, who was the chief of police in Bengal, India. They had a problem with tracking criminals through the legal system. The problem was, even if you used fingerprints to identify criminals, how do you possibly track and organize that information?
In 1896 Henry, or perhaps his Indian assistants, Azizul Haque and Hem Chandra Bose, developed a system for classifying fingerprints such it it would create 1,024 groups that fingerprints would fall under.
The classification system was adopted in India in 1897 and later by Scotland Yard in 1900.
This system was mostly used for identifying criminals who had already been through the system and had been fingerprinted. There were only rare cases, such as the one in Argentina, where an identifiable fingerprint would be left in some substance, such as blood.
Another big advance was developed by French scientist Paul-Jean Coulier who developed a method of lifing fingerprints off surfaces like glass, using iodine fuming.
The use of fingerprints spread rapidly in the early 20th century as it provided an easy way to track criminals and to link suspects to the scene of a crime if they left fingerprints.
Here I should address why it is out fingers leave imprints on some objects like glass or metal.
Even though it doesn’t seem like it, your fingers are covered in pores that excrete oil. In particular, these oils accumulate on the ridges on your fingerprints.
When you touch something, your finger acts like a rubber stamp, leaving an outline of your fingerprints in oil.
As fingerprinting became popular all over the world with law enforcement during the 20th century, there developed a problem.
By the end of the century, there were now tens of millions of fingerprints that had been collected. Even with a good classification system, the problem of matching a print found at a crime scene with someone who had already been fingerprinted was a daunting task.
To that end, in 1999, the United States Federal Bureau of Investigation launched the Integrated Automated Fingerprint Identification System or IAFIS. This was a giant database of all their fingerprints, which local law enforcement agencies could search.
A criminal search on a fingerprint can be conducted in about two hours, and a civil search can be conducted in about 24 hours.
While fingerprints have been a boon to law enforcement, they are not always perfect.
In 2004, there was a deadly terrorist attack on a commuter train in Madrid.
A partial set of prints found at the crime scene were run through the fingerprint databases, and they found a match. A lawyer, and Muslim convert, named Brandon Mayfield from Portland, Oregon.
Mayfield was arrested and held for two weeks. The fingerprints that they matched were taken from when he was in the Army.
The problem was, he was nowhere near Madrid and could easily prove it. He didn’t even have a valid passport and hadn’t left the country in over a decade.
While solving crimes has been the biggest use of fingerprinting over the last century, it hasn’t been the only one.
Fingerprints are unique identifiers, and there are many cases where you need to prove your identity. However, the system of having to dab your fingers in ink and storing them on cards, or even in a computer, still wasn’t convenient.
This problem was solved with the creation of fingerprint scanners.
There is a good chance that many of you have used a fingerprint scanner. They have been integrated into many models of smartphones, and they are often used by immigration police when entering a country.
There are several different types of fingerprint scanners that use different technologies to do the same thing.
The first type is an optical scanner. This just takes an image of your fingerprint to compare it to what has already been saved.
The next type is a capacitive or CMOS scanner. This type has electrical capacitors on the surface you put your fingers on, and they then take an image of your fingerprint using electricity. This type is usually the most accurate.
Another type of scanner is an ultrasonic scanner. This uses high-pitched sound to get a 3D map of the ridges on your finger.
The final type is thermal scanners. This uses the temperature differential between the ridges and valleys on your fingerprints. These are the least popular type of scanners.
Almost all smartphones use a capacitive touch screen to read fingerprints.
Despite fingerprints being unique, the capacitive fingerprint readers on smartphones aren’t that great. There have been many cases of people whose relatives were able to unlock each other’s phones using their fingerprints.
Likewise, hacking groups have been able to bypass fingerprint scanners over 80% of the time using off the shelf tools.
While these systems aren’t perfect, from a security standpoint, they are better than nothing. They work especially well when used in tandem with other methods of security.
I have a fingerprint scanner on the keyboard I use on my desktop computer. It allows me to quickly and easily bypass having to use my password for everything.
I’ll close by, noting a very rare condition called Adermatoglyphia.
Adermatoglyphia is a genetic condition that results in people completely lacking fingerprints. Their fingers are totally smooth.
As it is a hereditary condition, it tends to affect entire families. There are only six families worldwide who have been diagnosed with Adermatoglyphia.
There are no other known conditions associated with the anomaly, so if you had to pick a genetic disorder to have, this would probably be the one.
It has been dubbed “immigration delay disease” because it usually causes long delays at airport immigration control.
Fingerprints have been used for centuries and will almost certainly continue to be used for centuries to come. It isn’t just a unique identifier but an identifier that can be left behind at crime scenes.
The Executive Producer of Everything Everywhere Daily is Charles Daniel.
The associate producers are Thor Thomsen and Peter Bennett.
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