This tendon is linked to an ancient muscle called the palmaris longus, which was primarily employed by arboreal primates like lemurs and monkeys to move from branch to branch. As humans and ground-dwelling apes, such as gorillas, no longer rely on this muscle or tendon, both species have gradually lost internal function.
Nonetheless, evolution moves at its own pace – slowly – and approximately 90% of humans still have this vestige trait passed down from our primate progenitor. To determine whether you have this tendon, place your forearm on a table with your palm facing upward. Place your pinky finger next to your thumb and elevate your hand slightly off the surface. If you notice a raised band in the middle of your wrist, you have a tendon attached to the still-existing palmaris longus.
