Only 10% of the world population is left handed. But For left handed people of the world, life isn’t easy. Throughout history, stigmas were attached to left handedness such as them being unclean, witches, or possessed by the devil. Children with left handed tendencies were forced to use their right hand in school. The world has become more accepting of left handers, but there are still some difficulties. Most desks are designed for right handed people. The spine on spiral notebooks get in the way of writing for a left handed person. Papers are always smudged. Credit card swiping is difficult. Scissors are almost impossible to use.
Science
There are different theories about what makes a person left handed. But it is produced by biological and most likely genetic causes. A person is born either being left or right handed. And right handedness is a dominant gene. The most popular theory is related to language ability. Language ability is split between the different hemispheres (left and right parts) of the brain. And the left side of the brain controls the right side of the body, and vice versa. For most right handers, the part of the brain that govern language is the left side of the brain. And typically where the language skills are, so is the dominant body control. So if left side of the brain is used more for language it is also typical for right handed people. On the other hand, people who have language skills on the right side of the brain are usually left handed. And therefore since the right is the dominant side of their brain, they tend toward using the left hand.
Some other scientists have a theory that there is a genetic reason for handedness. They have found two genes that determine handedness, a C gene (chance gene) and a D gene (dexterity gene). The C gene is less common. If someone ends up with two C genes (CC) or one of each (DC) they are left handed. If they end up with two D genes (DD) they are right handed. This theory explains why left handedness is genetic. And it also explains why being left handed is less common, as the C gene is less common.
Left handers may be less common, but they leave their mark.
Left handers are smart. Left handed intellectuals include Albert Einstein, Isaac Newton, Charles Darwin and Benjamin Franklin, Marie Curie and Aristotle,.
Left handers are leaders. 8 US presidents have been left handed. Barak Obama, James Garfield, Herbert Hoover, Henry Truman, Gerald Ford, Ronald Reagan, George HW Bush, Bill Clinton. There may have been others, because prior to the 20th century, left handedness was considered a disability and children were taught to use their right hand despite being left handed.
Left handers are athletes. Phil Mickelson (golf) , Rafael Nadal (tennis) , Oscar de la Hoya (boxing), Bab Ruth (baseball) Lionel Messi (soccer), are all left handed.
Left handers are artistic. Leonardo da Vinci, Michelangelo, Rembrandt, Paul Klee and Pablo Picasso. Jimi Hendrix, Paul McCartney, Justin Bieber, Eminem and all modern left handed musicians.
Left handers are successful. Bill Gates, Oprah Winfrey, Steve Jobs and Mark Zuckerberg are lefties.

Fun facts about Left Handers
Left handers are better at multi tasking
Left handedness is twice as common in twins than in the general population
Studies suggest left handers are more talented in special awareness, math and architecture. They are artistic. Right handers are more talented verbally.
August 13 is “Left Hander Day”. The yearly event celebrates left handers and brings awareness to struggles of left handers
Left handers are more likely to have allergies, migraines, suffer from insomnia and be alcoholics.
Left handers recover from strokes faster.