🧬 Why Do We Have It? (A Glimpse into Evolution)
This muscle is a vestigial remnant—a leftover from our primate ancestors.
In tree-dwelling primates, the palmaris longus helped with gripping branches and climbing.
As humans evolved to walk upright and use tools, the muscle became functionally obsolete.
Over time, natural selection didn’t eliminate it entirely—so it persists in most people as a harmless anatomical quirk.
🌍 Fun fact: The absence rate varies by population:
~10–15% of people globally lack it
Up to 25% of some Asian populations are missing it
Only ~5% of Indigenous Australians lack it
🩺 Why Do Surgeons Care About It?
Because it’s non-essential, the palmaris longus tendon is often harvested for grafts in reconstructive surgery—like repairing damaged tendons in the hand, face, or even ACLs in the knee.
If you ever donate tissue, this might be the tendon they take—and you’ll never miss it.
✅ How to Test for It (Try This Now!)
Rest your forearm on a table, palm up.
Touch your thumb to your pinky.
