It is a common misconception that human evolution is a finished chapter—a relic of a primitive past that concluded once we began building cities and exploring the stars. In reality, our bodies are living, breathing archives of natural history, constantly undergoing subtle recalibrations so slow they remain nearly invisible across a single lifetime. When viewed against the vast timeline of the universe, our transition from forest-dwelling primates to a spacefaring civilization happened in the blink of an eye. Yet, biologically, we remain remarkably similar to our ancestors of 20,000 years ago. One of the most fascinating proofs of our ongoing biological “software update” can be found right now, hidden just beneath the skin of your wrist.
The Palmaris Longus: A Relic of the Canopy
The structure in question is a tendon connected to a vestigial muscle known as the palmaris longus. In the grand theater of evolution, this muscle was once a leading actor. For arboreal primates like lemurs and monkeys, the palmaris longus is a critical anatomical tool, providing the necessary forearm strength and grip tension required to swing effortlessly from branch to branch.
However, as certain primates transitioned from the canopy to the forest floor, the necessity of this muscle began to wane. Ground-dwelling apes, such as gorillas, have largely lost the function of this muscle because their locomotive needs no longer require that specific type of forearm leverage.
Humanity is currently following a similar evolutionary trajectory. Because we no longer rely on our forearms for primary movement or climbing, the palmaris longus has become “evolutionary baggage.”
The 15% Minority: A Glimpse into the Future
Evolution is rarely an all-or-nothing event; it is a gradual phasing out of traits that no longer provide a survival advantage. Currently, approximately 10% to 15% of the global human population is born without the palmaris longus.
Medical professionals note that the absence of this tendon does not result in any loss of grip strength or functionality in the modern world. In fact, it is so redundant that surgeons frequently harvest the palmaris longus tendon for use in reconstructive or plastic surgeries elsewhere in the body.
The Wrist Test: Are You ‘Fully Evolved’?
You can determine which side of the evolutionary curve you sit on with a simple, five-second diagnostic test at your desk:
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Place your forearm flat on a surface with your palm facing up.
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Touch your thumb to your pinky finger.
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Slightly tilt your hand upward toward your body.
The Result: If you see a pronounced, cord-like band popping up in the center of your wrist, you still possess this ancient climbing tool. If your wrist remains smooth, you are part of the small percentage of the population that has already moved toward an anatomical future where the palmaris longus no longer exists.
The Moving Target of Anatomy
This small tendon serves as a powerful reminder that while our world has changed beyond recognition, our bodies are still lumbering forward, shedding the remnants of the forest floor one generation at a time. We are, quite literally, works in progress.
Did you find a hidden tendon, or has your body already moved on to the next phase of human history? Let us know your results in the comments, and share this with your friends and family to see who among you is still carrying a piece of the ancient canopy!
