What If? Lab
What if everyone had the same fingerprints?
Look closely at your fingertips. You can see tiny lines and swirls! Everyone's are different. What if everyone's were the same? Let's find out with Olly!
The swirls and loops on your fingertips form before you are born, and no two people's are known to match, not even identical twins'. That's why fingerprints are used to tell people apart and to unlock phones. Imagine a world where everyone's fingerprints were exactly the same, and discover how they form, what they might be for, and what would change.
Fingerprints are patterns of skin ridges called dermatoglyphs. They develop between the third and sixth months of fetal development, shaped by genes and the environment in the womb, and even identical twins' differ. This thought experiment removes that uniqueness and asks what would change for grip, touch and identification.
The big question
Your fingertips have tiny lines. They make loops and swirls.
Your pattern is yours alone. What if everyone had the very same pattern?
Press your fingertip onto a window and you might leave a little print of lines, loops or swirls. Your fingerprints are yours alone: as far as anyone knows, no two people share the same ones.
So what if everybody's fingerprints were exactly the same? Would your fingers work any differently? What would change for detectives, for scientists and for your family's phone? Let's follow the clues.
Each person's fingerprints are unique, which is why, as MedlinePlus notes, they have long been used to identify individuals. That uniqueness comes from the fine details of the ridge patterns, not the basic shapes, which many people share.
This thought experiment makes every person's ridge details identical while leaving the ridges themselves in place. It follows three threads: how fingerprints form, what the ridges may do for grip and touch, and what identical prints would mean for fingerprint locks.
Explore the idea
Make a prediction
Do twins who look just alike have the same fingerprints?
Identical twins share the same DNA. Do they have the same fingerprints?
Do monozygotic twins, with identical DNA, have identical fingerprints?
- No, their fingerprints are different
- Yes, exactly the same
- Only on their thumbs
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Established fact
Fingerprints form before you are born.
Fingerprint ridges form between the third and sixth months of growth in the womb and stay the same for life.
Dermatoglyphs develop from the third to the sixth month of fetal development and persist unchanged (MedlinePlus).
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Established fact
Even twins have different fingerprints.
Even identical twins have different fingerprints, because tiny conditions while they grow shape the details.
Developmental factors, including the womb environment, make each person's prints different, even for identical twins (MedlinePlus).
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Established fact
Scientists are still finding out what fingerprints are for.
A 2009 test showed fingerprint ridges don't improve grip on smooth surfaces, so scientists are still working out what they are for.
Ridges reduced friction on a flat surface in a 2009 University of Manchester study; their function remains uncertain (Smithsonian; MedlinePlus).
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An idea scientists discuss
If all fingerprints matched, they couldn't show who you are.
If everyone's fingerprints matched, fingers might work the same, but fingerprints would be useless for telling people apart.
Identical prints would likely preserve ridge function while eliminating identification value.
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Established fact
Even twins who look just alike have different fingerprints.
Each person's fingerprints are unique; even identical twins, who share the same DNA, have different ones.
Each person's fingerprints are unique; identical twins, with the same DNA, have different fingerprints (MedlinePlus).
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An idea scientists discuss
If all fingerprints were the same, your fingers would still work.
If everyone's fingerprints matched, fingers might work just as well, but fingerprints couldn't tell people apart.
Identical ridge details would likely preserve whatever ridges do mechanically while removing their value for identification.
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Established fact
Fingerprints form before you are born and stay the same all your life.
Fingerprint ridges begin forming in the third month in the womb, are fully formed by the sixth month, and stay the same for life.
Dermatoglyphs begin developing in the third month of fetal development, are fully formed by the sixth, and remain the same throughout life (MedlinePlus).
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An idea scientists discuss
For everyone's fingerprints to match, everyone would have to grow in exactly the same way.
For everyone's fingerprints to match, every baby would need exactly the same genes and the same conditions in the womb, which doesn't happen even for twins.
Identical prints would require identical genotype and identical developmental conditions, a combination even monozygotic twins lack.
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Established fact
On smooth glass, fingerprint ridges don't make your grip stronger.
A 2009 University of Manchester test found that on a smooth surface, fingerprint ridges reduce how much skin touches it, which reduces friction.
Ennos and Warman found the ridges reduce contact area with a flat acrylic surface, reducing friction (Smithsonian magazine, 2009).
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Established fact
Fingerprints probably help you feel things.
Scientists aren't sure what fingerprints are for, but they likely make your fingers more sensitive to touch.
The function of the ridges is not entirely clear, but they likely increase sensitivity to touch (MedlinePlus).
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An idea scientists discuss
If everyone had the same fingerprints, holding and feeling would probably stay the same.
Whatever the ridges do for touch or grip, same-for-everyone ridges would probably still do it.
Grip and sensory roles depend on ridge presence and geometry in general, so identical details would plausibly leave them unchanged.
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Established fact
Phone fingerprint readers look at only part of your fingerprint.
Phone fingerprint sensors are small, so they scan and save only parts of your fingerprint, and many phones let you save several fingers.
Fingerprint-based systems on phones use small sensors that capture partial prints; identity is confirmed if a scan matches any saved partial print (NYU Tandon, 2017).
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Established fact
Parts of different people's fingerprints can look alike.
A 2017 study found that small parts of different people's fingerprints are alike more often than people expected.
Researchers found partial similarities between prints common enough that phone fingerprint systems could be more vulnerable than previously thought, and recommended multi-factor authentication (NYU Tandon, 2017).
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An idea scientists discuss
With the same fingerprints for everyone, people might use secret codes or other ways to unlock things.
In a same-fingerprint world, people might rely on passcodes, keys or other ways to prove who they are.
Identification would shift entirely to other factors, such as knowledge-based codes; which ones would dominate is speculation.
Fingerprints in our world
Fingerprints grow before you are born. They stay the same all your life.
Even twins who look just alike have different fingerprints!
Fingerprints form before you are born. According to MedlinePlus, from the U.S. National Library of Medicine, the ridges start to develop in the third month of growth in the womb and are fully formed by the sixth month. Then they stay the same for life.
Many people have the same basic shapes, such as loops, whorls and arches. But the tiny details are different for everyone. Even identical twins, who share the same DNA, have different fingerprints.
Dermatoglyphs, the skin ridges on fingers, toes, palms and soles, begin developing in the third month of fetal development and are fully formed by the sixth, then remain the same throughout life (MedlinePlus).
The basic whorl, arch and loop patterns may be similar between people, but the details are specific to each individual. Their size, shape and spacing appear to be influenced by multiple genes, while the finer details are shaped by conditions during development, including the environment inside the womb. That is why identical twins, with the same DNA, still have different fingerprints.
Make them all the same
Now pretend everyone has the same fingerprints.
Your fingers would still feel and hold things. But a fingerprint couldn't show who you are anymore.
If everyone's fingerprints were the same, your fingers might work just as well as before. The ridges would still be there, so whatever they do for touch and grip would probably carry on.
What would change is identity. A fingerprint left on a glass couldn't tell anyone who had held it, and a fingerprint lock on a phone couldn't tell its owner from anyone else. People would need other ways to prove who they are, like passcodes. These are ideas about a pretend world.
Making the ridge details identical would likely leave any mechanical or sensory function intact, since those depend on having ridges, not on their individual arrangement. That is reasoning, not a tested result.
What would be lost is information. Identification by fingerprint works only because the details differ between people; with identical prints, matching a print would reveal nothing about whose finger made it. Fingerprint-based locks would accept any finger, so systems would have to rely on other factors, such as something the user knows.
Why the details differ
Lots of things shape your fingertips while you grow before you are born.
Tiny differences make tiny changes. So every pattern turns out different!
Your genes help shape the basic size and spacing of your ridges. But while you are growing in the womb, many small things nudge the fine details, including the conditions around you as you develop.
That's why fingerprints are different even for identical twins: they share the same genes, but not exactly the same experience as they grow. To make everyone's fingerprints match, every single one of those tiny nudges would have to be the same for everyone.
MedlinePlus explains that genes controlling the development of the skin's layers and the muscles, fat and blood vessels beneath may all influence the ridge pattern, with multiple genes involved and no simple inheritance pattern. The finer details are influenced by other factors during fetal development, including substances taken during pregnancy and the environment inside the womb.
Identical fingerprints would therefore require identical development down to the finest details, which even genetically identical twins do not have. Surprisingly little is known about these factors, and few of the genes involved have been identified.
What are fingerprints for?
Scientists are still finding out what fingerprints are for.
They might help you feel things. Koalas have fingerprints too!
For a long time, people thought fingerprints help us grip, like the tread on a tire. But in 2009, scientists at the University of Manchester tested it. Smithsonian magazine reported that on a smooth surface, the ridges actually reduced how much skin touched it, which reduced friction.
So scientists are thinking again. Fingerprints might help with rough surfaces like tree branches, with wet surfaces, or with feeling things. MedlinePlus says their job isn't entirely clear, but they likely make your fingers more sensitive to touch.
The long-held grip explanation was tested in 2009 by biomechanist Roland Ennos and undergraduate Peter Warman at the University of Manchester, who measured friction between a fingertip and acrylic glass. As Smithsonian magazine reported, the fingertip behaved more like rubber, and the ridges reduced the contact area with the flat surface, reducing friction.
Candidate functions include grip on rough surfaces, grip on wet surfaces by channeling water away, and touch sensitivity; MedlinePlus says the ridges' function is not entirely clear but they likely increase sensitivity to touch. Humans, other primates and koalas all have fingerprints.
Amazing facts
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You have ridges on your toes and the bottoms of your feet too.
The same kind of skin ridges are found on your toes, your palms and the soles of your feet.
Dermatoglyphs occur on the toes, palms and soles as well as the finger pads (MedlinePlus).
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Koalas have fingerprints!
Humans aren't the only animals with fingerprints: other primates and koalas have them too.
Humans, other primates and koalas have fingerprints; all are, or have ancestors who were, tree dwellers (Smithsonian magazine).
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Fingerprint skin acts a bit like rubber.
In the 2009 Manchester test, a fingertip behaved more like rubber than a hard solid: flatter fingers touching more glass made more friction.
Friction depended less on force than on contact area, as with rubber; flatter fingers increased contact and friction (Smithsonian magazine, 2009).
Words to know
- fingerprint
- the pattern of tiny raised lines on the tip of a finger
- ridge
- a long, narrow raised line
- identical twins
- twins who come from the same egg and share the same DNA
- friction
- the force that resists one surface sliding over another
- unique
- the only one of its kind
- passcode
- a secret number or word used to unlock a device
Discovery challenge
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When do fingerprints form?
When do your fingerprints form?
During what period do fingerprint ridges develop?
- Before you are born
- When you start school
- When you become a grown-up
Show the answer
Before you are born
Before you are born!
In the womb, between the third and sixth months.
From the third to the sixth month of fetal development.
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Do twins who look just alike have the same fingerprints?
Do identical twins have the same fingerprints?
Do identical twins share fingerprints?
- No, their fingerprints are different
- Yes, exactly the same
- Only on their thumbs
Show the answer
No, their fingerprints are different
No! Even their fingerprints are different.
No. They share DNA, but tiny conditions in the womb make the details different.
No: developmental factors make the details differ despite identical DNA.
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What did scientists find when they tested fingerprints on smooth glass?
What did the 2009 test find about fingerprints on a smooth surface?
On a flat acrylic surface, fingerprint ridges were found to…
- They made the grip a little weaker
- They made the grip much stronger
- They made the glass wet
Show the answer
They made the grip a little weaker
The lines made the grip a little weaker on smooth glass.
The ridges reduced how much skin touched the surface, which reduced friction.
…reduce contact area and therefore friction.
Experiments to try
- Watch What If? Lab What if your skin could make food from sunlight? Plants catch sunlight and turn it into food, a process called photosynthesis. Imagine if your skin could do the same. Would you be able to skip meals? We'll compare how much energy your body needs with how much sunshine could give, and meet a real sea slug that keeps borrowed plant parts working inside its body.
- Watch What If? Lab What if you could see in the dark? Your eyes need light to see. Cats need only about a sixth as much light as people, thanks to a shiny mirror layer at the back of their eyes. And special cameras can 'see' infrared light, the invisible glow of warm bodies. Imagine having night vision and find out how it really works.
- Watch What If? Lab What if you had no thumbs? Your thumb is special: it can swing across your hand and touch the tip of every finger. That move lets you pinch, grip, write and use tools. Imagine a day without thumbs, then meet chimpanzees that grip with thumbs like ours and giant pandas that grasp bamboo with a clever 'pseudo thumb.'
Explore next
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Watch
Animal
Koala
The koala is a tree-living marsupial from eastern Australia. It eats almost nothing but eucalyptus leaves, sleeps up to 20 hours a day to save energy, and carries its jellybean-sized baby in a pouch that opens toward its back legs.
- Watch What If? Lab What if your skin could make food from sunlight? Plants catch sunlight and turn it into food, a process called photosynthesis. Imagine if your skin could do the same. Would you be able to skip meals? We'll compare how much energy your body needs with how much sunshine could give, and meet a real sea slug that keeps borrowed plant parts working inside its body.
- Watch What If? Lab What if you could see in the dark? Your eyes need light to see. Cats need only about a sixth as much light as people, thanks to a shiny mirror layer at the back of their eyes. And special cameras can 'see' infrared light, the invisible glow of warm bodies. Imagine having night vision and find out how it really works.
- Watch What If? Lab What if you had no thumbs? Your thumb is special: it can swing across your hand and touch the tip of every finger. That move lets you pinch, grip, write and use tools. Imagine a day without thumbs, then meet chimpanzees that grip with thumbs like ours and giant pandas that grasp bamboo with a clever 'pseudo thumb.'
- Watch What If? Lab What if germs did not exist? We often think of germs as bad, but many of the tiny living things around us are harmless or even helpful. About as many microbes live in your body as you have body cells, and they help you digest food and help your immune system develop, and helpful bacteria turn milk into yogurt and cheese. Imagine a world with no microbes at all, and see what we would lose.
- Watch What If? Lab What if humans had tails? Many animals use their tails to balance, to signal to each other, or even to grab branches. People and apes have no tails, but we each have a small tailbone at the bottom of our spine. Imagine life with a tail, meet monkeys that hang by theirs, and discover what scientists learned in 2024 about how our ancestors lost their tails.
- Watch Try it What If? Lab What if you climbed Mount Everest? The higher you go, the thinner the air gets. In this lab, travel from sea level to 8.8 kilometers, near the top of Mount Everest, using a model of the atmosphere. Watch the air pressure fall to about a third, the temperature drop far below freezing, and water boil at under 70 °C.
- Watch What If? Lab What if you could hear like a bat? People hear sounds from about 20 to 20,000 vibrations a second. Bats can hear sounds up to about 100,000. They shout out high calls and listen for the echoes to find insects in the dark: that's echolocation. Imagine bat ears, and discover the hidden world of sound all around you.
For parents & teachers
What children will learn
- Fingerprints form before birth and stay the same for life.
- Fingerprint details are unique, even for identical twins, because of conditions during development.
- Scientists are still investigating what fingerprints are for.
- Fingerprint identification works only because prints differ between people.
Recommended ages: 7 to 17 · About 15 minutes
Talk about it
- If fingerprints don't help grip on smooth surfaces, what else might they be for?
- Why can't genes alone explain fingerprints?
- What are the pros and cons of unlocking things with a fingerprint versus a passcode?
Try at home or in class
- Rub a pencil on paper to make a dark patch, press a fingertip into it, then press the fingertip onto clear tape and stick it on white paper. Compare prints with family members using a magnifying glass.
- Sort your family's prints into loops, whorls and arches. Are any two exactly alike?
Key vocabulary: fingerprint, ridge, identical twins, friction, unique, passcode
Where these facts come from
- Are fingerprints determined by genetics? , MedlinePlus Genetics, U.S. National Library of Medicine
- Fingerprints and Friction , Smithsonian magazine
- So You Think You Can Secure Your Mobile Phone With a Fingerprint? , NYU Tandon School of Engineering
Checked, not yet human-reviewed. Last updated October 26, 2026. Spotted a mistake? Tell us.