Opposable

This week, besides stitching our thumb and finger guards, we have been taking a closer look at the human thumb. It is generally well known that human thumbs are different from most creatures; this is because human thumbs are opposable.

 When a thumb is opposable it can be positioned opposite the fingers of the same hand. The thumb can then touch each of those fingers.

We are not alone

Contrary to popular opinion however, we are not the only living things to have opposable thumbs.  Koala bears, opossums, giant pandas, some species of arboreal frogs, chimpanzees, monkeys and some other primates also share this ability. However, humans have the greatest range of thumb movement.

This is because the thumb is controlled by 9 individual muscles and 3 major hand nerves. The movement of the thumb is more complex than that of the fingers. However the thumb consists of just two phalanges where as the fingers have three. This means the thumb is shorter. The thumb is also positioned lower on the hand and away from the other fingers. 

It is also only humans who can rotate the ring finger and little finger across the palm to touch the thumb. This is due to the flexibility of the carpometacarpal joints in the palm of the hand.

Survival

Whilst our first experience of our thumb might have been that it provides comfort, having opposable thumbs enables us to perform many complex tasks. It would be extremely difficult to pick up tiny objects or thread a needle without our thumbs.

Having opposable thumbs probably helped our ancestors survive too. Without them prehistoric man would have struggled to swing a club or launch a rock at his dinner.  Punching a beast on the nose in self defence would certainly have lacked effectiveness.

Julius Caesar shrewdly cottoned on to the importance of the human thumb in battle. He realised the enemy warriors would be incapable of using their weapons if their thumbs were no more. As such he promptly ordered amputations for all unfortunate captives.

This would have caused far more problems for the soldiers that just reducing their ability to fight of course. The loss of a thumb would have reduced the function of their hand by 40 %.

How much do you use your thumb?

Want to know just how important your thumb is to you? Try performing some of these tasks without using it.

Write your name using a pencil or pen

Brush your hair

Open a door using a knob

Tie your shoe lace

Put your socks on

Fasten a shirt

Blow up a balloon and tie a knot in it

Clean your teeth

Open a jar

Turn a tap

Make your bed

Read a book

Beat an egg

Of course there is one activity you should not try to do with your thumb. Do not try to read someone else’s pulse. Your thumb contains an artery called the princeps pollicis artery. Because all arteries pulse, its presence means you may be detecting your own.

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