Question

From anatomical position, perform opposition by rotating the thumb medially so that it touches the little finger. To demonstrate the importance of thumb opposition, grasp a plastic bottle as you normally would. Now, put the bottle down and grasp it again without using your thumb. Compare the two actions describing how effectively you were able to hold the bottle.

Answer 1

An opposable thumb is of evolutionary advancement that is a result of adaptation. Primates have opposable thumbs to climb branches and hold things easily.

With the above exercise, we can see that with the thumb, accomplishment of the task was much easier, quicker and less complicated. Thumbs were a physical adaptation for grasping. This was primarily used by primitive human for making tools and hence human have the most developed thumb out of all primates.

When holding a bottle without using the thumb, it takes much effort to grasp it, we scoop our palm and there are more chances that the bottle will fall out of our hands, whereas when the thumb is used, it covers the circumference of the bottle without scooping our palm. This shows not only importance of opponens pollicis muscle of the thumb, but also the importance of approximately 90° angle of the thumb with the rest of the fingers. Hence the thumb is said to be strategically placed for our own convenience.