The palmaris longus tendon test reveals whether you have a muscle that many scientists consider an evolutionary leftover. This tendon, located in the forearm, served an important role in climbing and wrist strength in early humans and primates. Today, a significant portion of the population no longer has it.
You can discover if you have this ancient structure in just a few seconds. The test is simple, visual and reveals how evolution shaped — and continues to shape — the human body.
Below is the complete palmaris longus tendon test.
Step 1 — Extend Your Arm and Turn Your Palm Up
Straighten one arm.
Rotate your palm upward so the wrist faces you.
Why this matters
This position exposes the forearm area where the tendon appears.
Step 2 — Touch Your Thumb to Your Pinky Finger
Gently bring your thumb toward your pinky finger.
Why
This tightens specific muscles involved in wrist flexion.
Step 3 — Slightly Flex Your Wrist Toward Your Body
Bend your wrist slightly inward while keeping fingers pressed.
What happens
If you have the palmaris longus tendon, it may become visible immediately.
Step 4 — Look for a Thin Vertical Tendon in the Center of the Wrist
Observe the middle of your wrist.
A thin, raised tendon may appear clearly.
Why
This is the tendon associated with the palmaris longus muscle.
Step 5 — Relax Your Hand and Try Again
Release your grip, then repeat the test.
What this reveals
Some people only show the tendon under specific angles or tension levels.
Step 6 — Test the Other Arm
Perform the same test on your opposite arm.
What happens
Some people have the tendon in one arm but not the other.
Why
The palmaris longus varies widely among individuals.
Step 7 — Compare the Visibility of the Tendon
Ask yourself:
- Is it visible in both arms?
- Is it visible in only one?
- Is it not visible at all?
Why
The palmaris longus tendon test highlights genetic variation linked to evolution.
Step 8 — Observe Any Differences in Wrist Tension
People who lack the tendon usually feel no difference, but some may notice:
- less tightness
- smoother wrist motion
- slightly different muscle activation
Why
The absence of this muscle does not impact wrist strength significantly.
Step 9 — Understand What This Muscle Was Used For
Early humans used the palmaris longus for:
- climbing
- gripping branches
- stabilizing the wrist
- applying force through the hands
Why
The muscle was far more important in species that depend heavily on brachiation and climbing.
Step 10 — What This Evolutionary Leftover Reveals About You
The palmaris longus tendon test reveals fascinating details about your evolutionary background:
1. Some people have it, some don’t
Around 10%–25% of the population lacks it completely.
2. It is disappearing gradually
Human evolution is reducing reliance on this muscle.
3. No functional loss
Surgeons often remove it for reconstructive procedures with zero impact on strength.
4. It highlights natural variation
Evolution rarely produces identical structures in all individuals.
5. It reflects our climbing ancestry
The tendon was useful for species that used their hands for locomotion.
6. It shows how the body adapts
Structures fade when they are no longer critical for survival.
The palmaris longus tendon test allows you to observe human evolution directly in your own body.
Next Evolution Experiment You Should Try
If the palmaris longus tendon test revealed an ancient muscle, the next experiment shows another evolutionary structure your body still carries — even though it lost its original purpose long ago.
Recommended next article:
“The Goosebumps Reflex Test — Discover Your Useless Ancient Superpower”
