Recently, for a background check for a visa, I had to get fingerprinted by an agent admissible to the FBI while I was still in France. No, we can’t fingerprint you, the website of the Embassy of the United States in Paris stated clearly. No, you can’t fingerprint yourself, the sites of the bureau-approved, USA-based channelers stated. Perhaps, I thought, I would gather my smirches—all those wasted on laptop screens, medicine cabinets, and eyeglasses—and dump them on a bureaucrat’s desk, like payment rendered in coin.

Instead, I fell on a National Fingerprint Collecting Clearinghouse technician named Eve Humrich. She has built a career on the fingertips of expats. I met her at her office on a mezzanine inside a squash club in Montmartre (though she travels between Paris, London, and Brussels for her clients). “I need to see your ID,” Humrich said. I showed my passport—using one type of identification to badge me into the realm of another. Humrich kissed each digit to a lubricious black pad, then onto an official paper card. With a small magnifying lens, she inspected the results: “These are nice and clear.”

On the walk home, while the sky pissed rain, I slipped the cards under my sweater. It occurred to me that I knew approximately zilch about how an identity could be apportioned in ten parts, each the size of a petal.

Thumb marks were used as personal seals to close business in Babylonia, and, in 1303, a Persian vizier recounted the use of fingerprints as signatures during the Qin and Han Dynasties, noting, “Experience has shown that no two individuals have fingers precisely alike.” The Chinese had realized that before anyone: a Qin dynasty document from the third-century B.C.E, titled “The Volume of Crime Scene Investigation—Burglary,” pointed up fingerprints as a means of evincing whodunnit.

In the mid-1800s, a British magistrate named William Herschel observed the Indian custom of inking hands or fingers alongside autographs or marks on contracts. Such agreements, he appreciated, were more often honored than disputed, and in the summer of 1858, Herschel started requiring prints on contracts with Bengali subjects. He credited their effect to superstition before seeing the truth: fingerprints actually did distinguish one person from the next.

Around the same time, a Scottish physician named Henry Faulds matched the greasy print from a drinking glass and the sooty print from a white wall to the criminals who had left them behind. Faulds wrote to Charles Darwin in 1880, asking the naturalist for help collecting “skin-furrows”—the ridges on fingertips reminded him of furrows in plowed fields. Faulds included cards and instructed Darwin to use printer’s ink, which could “easily be removed by benzine or turpentine” or by “burnt cork mixed with very little oil.” But Darwin was ill, and he punted the “curious” request to his cousin, the polymathic anthropologist Francis Galton, who had coined the phrase “nature versus nurture.” Galton took to the subject with gusto, piloting it toward science. (When Galton compared prints from “art-students” and “science-students” against “the worst idiots in the London district,” he found “no notable difference.”)

Mark Twain boosted the nascent forensic science into the realm of common knowledge with his novels Life on the Mississippi (1883) and Pudd’nhead Wilson (1894). The plots of both stories included murders solved with fingerprints (in the latter’s case, at a sensational trial). Galton had classified prints based on types of patterns, still known today as “Galton details,” but real-world fingerprinting for forensic application would struggle with a system to classify, index, and reference the marks for decades.

When French authorities interrogated Pablo Picasso, in 1911, at the Palais de Justice about the theft of the Mona Lisa from the Louvre that August, he was clad in his favorite red-and-white polka-dot shirt. Picasso cried. He begged forgiveness. He was in possession of two statuettes filched from the museum, but he hadn’t taken her. Among those sweating him was France’s great criminologist, Alphonse Bertillon, who, a decade earlier, had become the first investigator to solve a murder in Europe using fingerprint evidence. He was the originator of other booking procedures, such as the mug shot, and in The Hound of the Baskervilles, one of Sherlock Holmes’s clients insults Holmes by grading him “second highest expert” on the Continent, after Bertillon. Bertillon believed Picasso: the single thumbprint, left on the glass frame that shielded the painting, was not his. A couple of years went by with no leads. Only when the Italian who had carried her off—under the influence of lead poisoning—surfaced in Florence did Bertillon realize he’d had the culprit’s thumbprint on file all along. It was recorded from the right hand, while the mark was from his left.

In the twenties, the FBI’s first director, J. Edgar Hoover, created a national print pool: 7,000 law-enforcement agencies shared their fingerprint files, quickly amounting to 5 million sets. Hoover, John Lienhard, a professor emeritus of mechanical engineering and history at the University of Houston, explained to me, went on to use the theater of fingerprinting to define the FBI’s hi-tech look. “We heard a lot about how modern his FBI and his G-Men were.”

Even so, the prints were hard to use, Lienhard stressed. The FBI relied on a system of reference—worked out before the turn of the century by the head of London’s Metropolitan Police—that described fingerprints with symbols. “It was 1967 before we could read and compare prints optically.” Each request to search the database took months. In 1999, the bureau launched a computerized database, called the Integrated Automated Fingerprint Identification System. IAFIS was itself replaced in 2014 by the Next Generation Identification Program, which records additional biometrics, such as moles, scars, and tattoos. Stephen G. Fischer, Jr., a chief in the FBI’s Criminal Justice Information Services Division, told me in early May that the repository holds 123,027,098 fingerprint sets, 74,851,046 of which are criminal. “The overall average response time for criminal submissions is 8 minutes 15 seconds,” he specified. Before DNA technology, the sexiest clues at crime scenes were fingerprints—a latent residue of salts, amino acids, and lipids, dusted into revelation.

Scientists describe the basic patterns of fingerprints in terms of arches, whorls, and loops. (Seventy percent of a fingerprint is made up of loops.) Closer features include dots, lakes, islands, spurs, crossings, and bifurcations. It is true that every print is unique to every finger, even for identical twins, who share the same genetic code. Fingerprints are formed by friction from touching the walls of our mother’s womb. Sometimes they are called “chanced impressions.” By Week 19, about four months before we are issued into the world, they are set. Gorillas, chimpanzees, and koalas also possess exclusive prints. Those of koalas have been reported as indistinguishable from those of humans—with some outlets claiming that the similarity has tripped up Australian crime scene investigators. I wondered about this. Envisioning a place strewn with eucalyptus leaves by animals desperate to get their backgrounds checked, too, I reached out to the police in New South Wales for a fact-check. Senior Sergeant Peter Hennessy, a fingerprint expert, was good enough to reply:

I am pleased to report koalas do in fact have fingerprints which are similar to humans!!! I have however looked at some fingerprints/paw prints (?) taken from koalas and they were all much poorer quality than most humans fingerprints, probably because koalas are constantly in contact with rough trees and the skin on their paws is much rougher than human skin. Furthermore, the lines or ridges of a koala’s prints appear ‘dotty’ and are generally not as continuous as a human’s fingerprints. So although someone without fingerprint training may not be able to distinguish those from and a koala or a human, I am reasonably confident a qualified fingerprint expert would observe some differences between the two. And although it would make for a good story, unfortunately I have never heard of Australian Crime Scene Examiners mistaking a koala’s fingerprints with those from a human.

In puberty, when hands turn oiler, prints left on surfaces last longer; they become trickier to capture with age, as epidermal ridges harden. Some people’s prints just never stand out, and techs like Humrich may plunge their clients’ hands into ice water to bring them into definition. You can erase your physical prints for a time, as my father accidentally did by working with battery acid. The wearing down of ridges was, historically, an occupational hazard shared by bricklayers and secretaries, the second from handling paper. Fingerprints grow back. Barring mutilation, they are a biometric for life—even in death. Che Guevara was interred without his hands—lopped off, sent to Argentina for fingerprinting. You can, and people have, fingerprinted Egyptian mummies.

Most interesting is how this ancient biometric is now on its second wind. More and more, the path forward obliges us to submit our fingers to screens. In New York for the visa appointment, the consulate scanned my prints. (“Madame, concentrate,” the functionary snapped when their machine rejected my trembling hand.) Days later, in security at LaGuardia Airport, I jumped out of the long line upon hearing “Skip this in three minutes, folks. Enroll with Clear.” The subscription-based biometric platform acts as a fast pass for checkpoints at twenty-four airports and twelve stadiums across the United States so far. Caryn Seidman Becker bought the bankrupt company in 2009 and relaunched it the next year, starting at Orlando International Airport, which sees the highest number of first-time travelers. In the past couple of years, Clear has nearly quadrupled in size to serve two million customers.

At LGA, my fingers and eyes were scanned at a kiosk. I gleefully skipped the state- or federal-issued ID and boarding pass routine and proceeded straight to the X-ray machines. “Our mission is two-part,” Becker told me by phone, “strengthening security and frictionless experiences.” (Never mind that friction in baby’s first port of entry is what gave us fingerprints to begin with.)

The CEO said there is debate as to which are more secure: fingerprints or iris images. Both have tested to be 99.999 accurate, but not everyone’s fingertips cooperate. “Facial is good and getting better,” Becker added. Clear—a proprietary software—works with all biometrics. “We’re agnostic as to which one our partners use,” she continued. “Our view is that different biometrics have different use cases.” In an active case, someone would trot through a checkpoint and have their face scanned without ever stopping (“face on the fly,” Becker called this); in a passive case, someone would pause to lay down their fingers.

Clear just won biometric aid contracts with Washington State and Clark County, which includes Las Vegas, to start IDing people at bars. The applications for biometric identity products are broad. Wallets and keys might get lost for good if we can pay for cappuccinos and power up cars with our eyeballs or fingers. In the early aughts, when we were increasingly imagining a future where people moved through the world—for better or worse—without anonymity, those people were chipped. But who needs computer chips when you’ve got fingerprints? “The future of biometrics has never been better,” said Becker. “Biometrics have gone mainstream—now people have expectations and habits. People are checking into every Delta Sky Club in the country with biometrics.”

A rumor persists that the Soviet Union and the People’s Republic of China selected Olympians in the seventies partly based on their fingerprints, which were believed to express prowess. As it turns out, since our prints and neocortices are in development at the same time, and are subject to the same intrauterine effects, the patterns on our fingers do seem to correspond to the lobes of our brains. Some researchers are hailing fingerprints as blueprints. “Fingerprints are the mirrors to our inborn talents and potentials, knacks and likings,” write the authors of one recent paper, who believe people may be able to use their fingerprints to unlock their best selves. Plus, in an act almost like palm reading, studies show that the swirly labyrinthine lines correlate with risks for many conditions, including diabetes, asthma, autism, periodontitis, schizophrenia, gastrointestinal cancers, and infertility. It means that specialists have another tool for early diagnosis: our identity is mapped at our fingertips, but also, maybe, our individual fate.

Tapplock, the first biometric paddock, and one capable of storing 500 different fingerprints, started shipping last year. Most smartphones read thumbs. Al Franken grilled Apple CEO Tim Cook in 2013 about the iPhone’s then-new Touch ID technology, saying, “Let me put it this way: if hackers get a hold of your thumbprint, they could use it to identify and impersonate you for the rest of your life.” The latest Apple laptops accept fingerprints. The radio frequency identification (RFID) chips in biometric passports stash our prints—compelling people like my boyfriend to disable the thing with a hammer. To be fair, it’s a real concern: in February, Wired reported that U.S. Customs and Border Protection has failed to deploy the software that shows if e-Passport data has been jiggered with or forged. “That could theoretically be enough to slip into countries that allow all-electronic border checks, or even to get past a border patrol agent into the U.S.,” Lily Hay Newman, the magazine’s security reporter, intoned. “Where are you now my fingerprints?” Leonard Cohen croons in a song adapted from “Give Me Back My Fingerprints,” a poem he published in the sixties. Cohen believes he lost his fingerprints—his identity—by touching his lover too much too often. So much of our selves are in our fingers.

Chantel Tattoli is a freelance journalist. She’s contributed to the New York Times Magazine, VanityFair.com, the Los Angeles Review of Books, and Orion and is at work on a cultural biography of Copenhagen’s statue of the Little Mermaid.