No-one has come up with a definitive reason for WHY some people are left-handed, but about 13% of the population around the world are, and it is thought to be genetic - it definitely runs in families. Researchers have recently located a gene they believe "makes it possible to have a left-handed child " so if you have that gene, one or more of your children may be left-handed, whereas without it, you will only have right-handers - sorry! The good news is, that if you are left-handed yourself, you have that gene and will pass it on through the generations!
The way the brain works is incredibly complex, but this simplified explanation will give you some understanding of where our left-hand dominance comes from. The brain is "cross-wired" so that the left hemisphere controls the right handed side of the body and vice-versa and hand dominance is connected with brain dominance on the opposite side - which is why we say that only left-handers are in their right minds!
The left hemisphere (RIGHT HAND CONTROL) controls Speech, Language, Writing, Logic, Mathematics, Science, this is the LINEAR THINKING MODE.
The right hemisphere (LEFT HAND CONTROL) controls Music, Art, Creativity, Perception, Emotions, Genius, this is the HOLISTIC THINKING MODE
Effects of right brain dominance
This brain dominance makes left-handers more likely than right handers to be creative and visual thinkers. This is supported by higher percentages of left-handers than normal in certain jobs and professions - music and the arts, media in general. (See the results of our Lifestyle Survey of Left-Handers for our detailed findings) Left-handers are also generally better at 3-dimensional perception and thinking, leading, for example, to more left-handed architects than normal. Left-handers are also usually pretty good at most ball sports and things involving hand-to-eye co-ordination.
The view that left-handers are clumsy and awkward is not down to their natural abilities, but being forced to use right-handed tools and machinery which is completely back-to-front for them.
If you are interested in the latest research and findings on left-handedness, you can buy the excellent book Right-Hand, Left Hand by Chris McManus in the online shop.