Your Paw-some Question | Why do we have fingerprints?

Today Cosmo and I learned all about fingerprints—and how they give primates dexterity and grip. 

• Learn more about primates from PBS
• Find out how gecko feet work with ACS
• Check out your fingerprints with SciShow Kids—or investigate them with PBS

Sound effects courtesy Pixabay

 As always, submit burning questions at askdruniverse.wsu.edu.  Who knows where your questions will take us next.

Transcript

Hey, Doctor Universe.

Hey, Cosmo.

What kind of a job does a gecko work?

I don't know. 

Retail.

Hey, friends, I'm Doctor Universe.

And I'm Cosmo. 

And if you're anything like us, you've got lots of big questions about our world. Today, we're answering a question sent in by a kid just like you. 

Calin wants to know: Why do we have fingerprints?

Cats like us don't have fingerprints. We don't even have fingers. But scientists think there are two big reasons humans have fingerprints: dexterity and grip.

Dexterity is the way they use muscles in their hands to make small, precise movements. That's how they write, type, or use a game controller. It's also called fine motor control. 

To make those exact movements, they take in data and make little adjustments. That data comes from what they see and hear. It comes from what they feel and how they sense their bodies in space.

Like when I'm gaming, I adjust my paw movements based on what I see and hear in the game and in the real world.

Yeah, you feel the controller. You can tell how your paws are moving. Your brain uses all that information to tune your movements.

The sense of touch works because the skin has tiny touch sensors. They're called Meissner's corpuscles. They help you feel different textures. Primates like monkeys and apes have lots of these. Humans are among the apes with the most, and theirs are really big. 

Scientists think the ridges of fingerprints act like little levers. As a human touches something, those ridges push on touch sensors. That gives the brain lots of information about what they touched.

It's possible that dexterity evolved as primates began eating more fruit. Being able to feel subtle textures would have helped them figure out if fruit was ripe. 

Nobody likes a green banana.

Grip is how you hang on to things. Humans need their fingers to be moist, but not sloppy. If the skin is too dry, it won't flex right. If it's too wet, they'll lose friction and slip off. 

The ridges of fingerprints are like tiny furrows or channels that move moisture. Those ridges spread the sweat around so the skin is flexible but not too slippery. Fingerprints also help grip rough surfaces because the ridges lock in with the bumps and grooves on the surface.

Some animals do this super well. It's how geckos cling to smooth surfaces like glass with their mega-ridged feet. 

That's a slick move.

Animals usually don't evolve traits that do just one thing. Fingerprints helped early humans succeed in a few ways. So those fingerprints stuck around. 

That's why humans form fingerprints way before they're born. The unique pattern of ridges happens because of genes, the density of the fluid inside the uterus, and how the fetus moves around while the ridges form.

I bet that adaptation gave humans a hand up on the competition.

That's all for this episode, friends. 

Big thanks to Katherine Korn, an evolutionary functional morphologist at Washington State University. 

As always, if you've got a science question for me, you can submit it at askdruniverse.wsu.edu. That's a s k d r u n i v e r s e dot w s u dot e d u. 

Who knows where your questions will take us next?