If A Tendon Pops Up When You Touch Your Thumb To Your Pinky, This Is What It Means

It might sound a little odd, but it’s true. From wisdom teeth to the way some people can wiggle their ears, much of what we are today reflects what our animal ancestors needed for survival.

As explained in a Vox video, these strange remnants stuck around because they weren’t “costly” enough to disappear through millennia of evolution. They only make sense when we look at things through the lens of natural selection.

Here’s an example you can see for yourself. Hold your arm out, touch your thumb to your pinky, and you might notice a raised tendon in the middle of your wrist.

If you don’t see it, congratulations—you’re one of the lucky 10-15% of humans who were born without this feature in one or both of their arms.

That tendon is connected to a muscle called the palmaris longus.

Most people have it, but it doesn’t seem to serve any real purpose. 

YouTube / Vox

Research shows that having this muscle doesn’t give you any more arm or grip strength compared to those who don’t have it.

In fact, surgeons often remove it and use it for reconstructive or plastic surgery elsewhere in the body because it’s so inconsequential.

So, why do we still have this muscle if it’s not useful?

Scientists have discovered that the palmaris longus is present in many mammals today, especially those that use their forearms to move around, like lemurs and monkeys.

For them, it’s useful. But for us, it’s more of an evolutionary leftover.

Here’s another quirky feature: can you wiggle your ears? If you can, great job! You’re showing off another evolutionary remnant.

This skill, once essential for our ancestors, is now a party trick that’s mostly just fun to show off.

Many nocturnal animals, like rabbits, gazelles, and cats, rely on their ears to locate the source of a sound by turning them in various directions. 

Millions of years ago, the creatures we evolved from used the same trick. 

We haven’t completely lost this ability.

As Vox explains, humans still have three muscles involved in ear movement. Studies show that these muscles still respond to sound, though not enough to move our ears. They try, but it’s not quite there anymore.

There are plenty of other examples of odd things our bodies hold onto from our ancient ancestors. 

Think about goosebumps. They don’t do much for us today, but for our ancestors, they helped trap heat by raising their body hair.

And that little tailbone at the base of your spine? Another leftover.

Marvel Studios

Even babies grasping your finger when you put it in their tiny hands is a reflex passed down from our past.

If you’re lucky enough to live near a Natural History Museum, you can see fossils and remains of animals that show how species, including humans, evolved over time. But if you don’t have access to one, don’t worry. You’ve got one of the most fascinating living specimens with you right now—your own body!

Think about all the things we don’t need anymore. Take body hair, for example. We have clothes now, so body hair and goosebumps are mostly just minor irritations. But our ancestors needed body hair for warmth, and goosebumps helped increase the surface area of their skin to trap heat.

Another evolutionary leftover is the remnants of a third eyelid, and of course, wisdom teeth—those useless extra teeth we don’t really need to chew food anymore. But what’s even more fascinating is how humans are still evolving.

If you think evolution is over, think again. What will humans look like 5,000 years from now? It’s exciting to imagine. They might seem strange to us, just as we seem strange to our distant ancestors.

That brings us back to the palmaris longus, the “tendon of the hour.”

It’s located in your forearm, and if you have it, you can easily see it by turning your palm face up, bending your wrist, and closing your fingers.

The tendon will pop up at the base of your wrist.

So, who doesn’t have this tendon? About 10-15% of people today don’t have it, and they’re perfectly fine without it.

If you’re one of them, congratulations—you’re a little further along in the evolutionary process.

And if you still have the tendon, well, you’ve learned something about your ancestral past without even needing a trip to a museum.

This could be a fun way to start a conversation about evolution or even get kids interested in Natural History.

Do you have the tendon? What about your friends? It’s a fun opportunity to explore our shared evolutionary past.