An example of an original trait in humans that is now extremely rare or non-existent is the presence of a specific type of muscle called the palmaris longus muscle.
The palmaris longus muscle is a thin, narrow muscle located in the forearm, running from the elbow to the wrist. It is considered a vestigial muscle, which means it served a more functional purpose in our evolutionary past but has become less significant or disappeared over time due to changes in human anatomy and lifestyle.
While the palmaris longus muscle was present in the ancestors of modern humans and was used for activities like climbing and gripping, not all individuals possess this muscle today. In fact, approximately 10-15% of people lack the palmaris longus muscle bilaterally (in both arms), and some individuals may only have it on one side.
The absence of the palmaris longus muscle is often discovered through a simple physical examination known as the "Schaeffer's test" or "Schaeffer's sign." The test involves certain maneuvers to evaluate the presence or absence of this muscle in the forearm.
With advancements in human evolution, changes in lifestyle, and decreased reliance on certain physical activities, traits like the palmaris longus muscle have become increasingly rare or non-existent in the human population.