Are you left-handed?
If so, one in ten people around the world is like you.
However, nine out of ten people are right-handed.
Stone tools suggest that most of our ancestors were, like most of us,
right-handed.
It's hard to pin down when left-handedness started,
but we do have evidence that there were left-handed Neanderthals
500,000 years ago.
How do we know this?
Well, they were probably eating raw meat, which is tough old stuff.
Archaeologists think the Neanderthals would sink their teeth in,
and then use a sharp piece of stone to cut the meat near their mouth.
Sometimes the stone slipped.
And from the direction of the scratches,
10% of Neanderthals seem to have held the cutter in their left hand.
For right-handers, it's normally the left side of the brain
that's associated with speech and language.
What though if you are left-handed?
Despite using their left hand for writing,
two thirds of left-handers are just like right-handers,
in having language in their left brain.
But, a third of left-handers
have language in the right side of their brain -
the opposite of right-handers.
Left-handers are much more variable
in the ways their brains are organised.
In contrast, right-hander's brains are off-the-peg.
Left-handedness is therefore much more of a mixture
of strengths and weaknesses, pros and cons
coming from having a somewhat differently organised brain.
Is your baby sucking its thumb?
Psychologist Peter Hepper in Belfast
studied several hundred scans
where the baby in the womb was seen sucking its thumb.
About 90% of babies sucked their right thumb.
And at twelve years old,
almost all of those right thumb suckers were right-handed.
Whereas three-quarters of the left thumb suckers
would become left-handed.
Genes are clearly also important.
One left-handed parent,
and you're more likely to be left-handed yourself.
Both parents left-handed, and you're even more likely.
About a one in four chance.
Infants often go through a random chaotic phase
where they use the right hand one day, and the left the other,
perplexing their parents.
By about two-years-old, their handedness is usually consistent.
If you practise long and hard enough,
then you can probably do anything equally well with either hand.
Concert pianists are a good example, though it does take dedication.
In 1797, the right-handed Admiral Lord Nelson,
had his right elbow shattered by a musket ball.
The arm was amputated.
Within six months though,
Nelson had learnt to write fluently with his left hand.
But the motivation was there, of course.
Professional sports players are also motivated to practise,
as it can give an added edge in competiton.
Footballers train to kick well with either foot,
and when practising they use both feet confidently and well.
But under pressure, when the action's hot,
they often revert to using their dominant foot.
Even if it means taking an extra half-step before shooting for goal.
Reversing your natural sidedness does come with a cost.
You could be almost equally good with each hand or foot,
but the price would be so much time practising,
that you probably wouldn't do anything else with your life.
The list of famous left-handers seems pretty impressive.
Albert Einstein, Beethoven, Bob Dylan, Picasso, Neil Armstrong,
Winston Churchill, Benjamin Franklin, Marilyn Monroe,
all are claimed, on the internet, to be left-handed.
And in each case, it's almost certainly wrong.
The evidence of left-handedness is often very dodgy indeed.
For instance,
there's a book with a painting of Beethoven writing with his left hand,
the picture has clearly been flipped.
There are many reasons why people may wrongly claim
that famous individuals are left-handed.
Tribal loyalty and the reflected glory
of feeling part of the same handedness club are just two of them.
Perhaps when it comes down to it,
there is a little bit of the left-hander in each of us.