Finger counting

ASK A SCIENTIST
Last updated 13:47 10/11/2009

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Samantha Fox, of Ardgowan School, near Oamaru, asks: "Why do we have five fingers?"

Gareth Jones, a structural biologist at the Otago School of Medical Sciences, responds.

In order to answer this question, we have to think about the hand with its fingers, and not about the fingers alone.

This is because the fingers are a very important part of our hands, and it is the hand as a whole that is so important.

When we think about the hand, do we have five fingers, or is it four fingers and a thumb?

The answer is – four fingers and a thumb, because the thumb is very different from the four fingers.

It is shorter and stockier than the fingers, and, even more important, it faces the other fingers.

The human hand is broad, and what this allows us to do is to "oppose" our thumb. What this means is that we can bring our thumb across to touch the tips of our four fingers.

This is essential if we are to pick up small things, and manipulate fine objects.

Without this, we couldn't hold a pen or a brush, turn screws, cling on to objects, hold a ball, or play the piano or guitar. All these allow us to carry out what are the normal activities of everyday life for people like you and me. This is part of what makes us human.

The thumb is probably more important than any of the other fingers.

We can lose one or two fingers and still do most normal things with our hand.

But if we lose our thumb, we find that normal activities become very difficult, if not impossible.

Send your questions to Ask A Scientist, PO Box 31-035, Christchurch 8444, or email questions@ask-a-scientist.net

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