Are you part of the 14% of the global population who do not have this particular muscle? If so, it may mean that you are more evolved than others.
Put your hand in the air and touch your thumb to your pinky finger. Can you see a raised tendon on your wrist? This muscle is called the palmaris longus.
The evolutionary progression of Man
Orangutan and lemur like to swing from tree to tree. If they are able to do so, it is thanks to the palmaris longus muscle in their wrists.
Between the flexor carpi radialis and the flexor carpi ulnaris in the wrist, you will find the palmaris longus muscle. This muscle makes it possible for mammals to throw themselves around, or to hang out in the trees; few activities we don’t (often) indulge in.
As man evolved, thumbs took over, and the muscles started strengthening around there. Even though the palmaris longus is a vestigial muscle now, it does still have a few benefits.
Palmaris longus provides wrist flexibility. The muscle operates in tandem with the forearm's long flexors, to provide flexion at the wrist joint and other tiny joints of the hand.
Even though the prevalence of palmaris longus muscle in the upper arm has no importance, the muscle assists in the tightening and tensing of the palmar aponeurosis, or the central dip of the palm.
Thus, in the anatomy of the grip, this muscle plays a vital role.