Interesting. Most people are "both" to a greater or lesser degree.Tennis champions and fencing champions are almost 50% left handers. One theory is that reaction times are faster because the right brain is connected directly to the motor centres and can make quicker decisions. A rightie has to process in the left brain, then transfer to the right brain to action the decision.
More interesting is the extent to which people use the capacities of both sides of their brain in everyday life. There are several tests which you can self administer to see which bits you are'nt bothering with!
I spent 10 years fencing right handed to quite a reasonable standard and then switched to my left hand when I was 25 and discovered a whole new sport! Then when I started flying the Class 1 initial Doc told me with great glee that I was an interesting specimen because I had no dominant eye. I was bang slap in the middle of their eye balance tests."You'd have made a jolly good shot as a fighter pilot". Ha! Now he tells me!
Also interesting are the horrific but fascinating results of the the experiments in the fifties when the link between left and right brain was severed in an experimental "cure" for epilepsy.
Most "activity" was centred in the left brain(of course in a right handed sample it would be) so what was the right brain good for? it appeared to have an upsurge in activity during siezures...so...guess what. Let's cut the link between the 2 hemispheres, they'll never know what they are missing....
Dont know if anyone has any links to the results.