There is a great article on "handedness" and what it reveals of the workings, development and structure of the brain in the Philadelphia Inquirer: The mysteries of lefthandedness by Faye Flam:

With brain scanning and the latest genetic technology, scientists are finally starting to crack the mysteries. Lefthanders really are special, and the ways they differ are yielding insight into human diversity - especially how one person's brain differs from another's.

"Its a quirky phenomenon of humans, and people ask why it's relevant," says research geneticist Clyde Francks of Oxford University. "But this is taking us into a fundamental feature of the human brain."

"Lefthandedness is connected to a lot of neurodevelopmental disorders," says Daniel Geschwind, a UCLA expert in what is known as neurobehavioral genetics. People with autism and schizophrenia are more likely to be lefthanded, he says. "But with that risk, there is also gain."

Look at MIT professors or musicians or architects, he suggests, and you'll see a slightly higher percentage of lefthanders than in the general population. Neuroscientists are beginning to figure out why.

The brains of lefthanded people develop more freely in utero, they say, allowing the organization to stray more from the standard design.

It comes as no surprise to those few of us who take our own hands seriously, that the hands provide such a clear view into the workings of the brain, or that lefthandedness would be associated with human diversity. Handedness was one of the interesting subjects discussed in The Anthropology and Social Significance of the Human Hand by Ethel J. Alpenfels, D.Sc. as follows:

HANDEDNESS IN MAN
RIGHT AND LEFT—GOOD AND EVIL
The cultural world in which man lives, both in preliterate and in technologically advanced societies, tends to be a "right-handed" world. Cross-cultural studies reveal that different sides of the body, the left or the right, are associated with different social activities. In India, the right side and the right hand perform tasks considered to be "clean," while the left side and the left hand perform tasks considered to be "unclean." The two types of activities are separated rigidly. The right hand, for example, is used for cooking and eating, whereas the left hand is used in bathing, elimination, or activities associated with sex. Indeed, it is common in many areas of the world to find food related to the right hand, while the left hand is associated with sex.

The right and left hand have come to symbolize good as opposed to evil, gods as opposed to demons. Hence, they are considered as two forces constantly at war with one another. The shadow plays of the Balinese illustrate the widespread association of good and evil with the right and left side respectively. The mystic story teller takes the marionettes out one by one, placing the "good" and "noble" characters at his right side and, at the left, the "evil" and "sinister" characters. In the end, truth and goodness always win, which demonstrates the triumph of the magical powers of the right side. At all important life crises—birth, death, marriage, initiation ceremonies—this magic balance between left and right is maintained.

It is fortunate that in our modern times, we are able to look less fearfully at our diversity, and to use the tools we have been given and have created to gain greater insight. As further discussed by Dr. Alpenfels:

Can the custom of men buttoning their coats on the right side and women on the left be a survival from our primitive past when the right was reserved for men because it was "good" and the left for women because it was "evil"? Our society is belatedly recognizing the right of sinistrodextral people to full participation in our culture. Banks are issuing left-handed checkbooks, left-handed armchair desks have been introduced in schools, and left-handed scissors and other implements and tools now are available.

You might be curious about the word used by Alpenfels, sinistrodextral. Its origins are as follows:

sinister 1411, "prompted by malice or ill-will," from O.Fr. sinistre "contrary, unfavorable, to the left," from L. sinister "left, on the left side" (opposite of dexter), perhaps from base *sen- and meaning prop. "the slower or weaker hand" [Tucker], but Buck suggests it's a euphemism (see left), connected with the root of Skt. saniyan "more useful, more advantageous." The L. word was used in augury in the sense of "unlucky, unfavorable" (omens, especially bird flights, seen on the left hand were regarded as portending misfortune), and thus sinister acquired a sense of "harmful, unfavorable, adverse." This was from Gk. influence, reflecting the early Gk. practice of facing north when observing omens; in genuine Roman auspices, the left was favorable. Bend (not "bar") sinister in heraldry indicates illegitimacy and preserves the lit. sense of "on the left side."