When you sign your name, odds are good that you will do so with your right hand. Only about 10 percent of people worldwide are left-handed, experts say. They're more comfortable writing, throwing a ball and doing other manual tasks with their left hand.
In fact, one of the more unusual hypotheses to explain the rarity of left-handedness is that a genetic mutation in our distant past caused the language centres of the human brain to shift to the left hemisphere, effectively causing right-handedness to dominate, Alasdair Wilkins explains for io9 back in 2011.
The countries that use right-to-left writing systems are predominantly Arab and Asian and they all have left-handedness rates below 6 per cent. In Muslim countries, the advantage of smudge-free handwriting is outweighed by the fact that the left hand is considered unclean.
One biological effect on hand preference is known to be sex, with males more likely to be left-handed than females2,14. For example, in a U.S. dataset aged 10–86 years, the proportion of non-right-handers among 664,114 women was 9.9%, versus 12.6% among 513,393 men2.
Right-handed people are more skillful with their right hands. Studies suggest that approximately 90% of people are right-handed. Left-handedness is less common. Studies suggest that approximately 10% of people are left-handed.
Babe Ruth. The Babe is probably the most famous left-handed slugger of all-time.
Special or not, lefties are born, not made: Genetics are at least partially responsible for handedness. Up until last year, it was assumed that hand preference comes from asymmetrical genes in the brain—two hands, two brain hemispheres, one is dominant.
McManus which found that the Netherlands has one of the world's highest prevalences of left-handedness at 13.23 percent. The United States isn't far behind with a rate of 13.1 percent while neighboring Canada has 12.8 percent. Elsewhere, rates of left-handedness are far lower and China is a good example.
Abstract. Left-handedness occurs in about 8% of the human population. It runs in families and an adoption study suggests a genetic rather than an environmental origin; however, monozygotic twins show substantial discordance.
Hand preference probably arises as part of the developmental process that differentiates the right and left sides of the body (called right-left asymmetry). More specifically, handedness appears to be related to differences between the right and left halves (hemispheres ) of the brain.
In many Islamic countries, people are forbidden to eat with their left hand which is considered 'unclean' because it is used for cleaning the body after defecation. In addition, 'public display' or use of the left hand is against the law in some Islamic countries, including Saudi Arabia.
The left hand is used to clean bodily excrements and viewed as unclean. The right hand is the clean hand used for eating, shaking hands etc.
Sex – slightly more boys than girls are left-handed. This suggests to some researchers that the male hormone testosterone has an influence on right and left-handedness. Fetal development – some researchers believe that handedness has more of an environmental influence than genetic.
They are usually good at sports when in a one-on-one face-off. In games like baseball, boxing, fencing and tennis, left-handers often have an edge over their right-handed opponents who are used to playing with right-handed players mostly. Left-handers have typing advantages.
If two parents are right-handed, their offspring has a 10% chance of being left-handed. However, if one or both parents are left-handed, the chance of their child being left-handed becomes higher at 18 to 22% and 27%, respectively.
To be left-handed, both copies would have to be the left hand gene. That also means two lefties would always have left-handed children. This is not the case for your family or lots of others either. For example, if both parents are right-handed, there is a 1 in 10 chance of having a left-handed child.
Left-handedness was associated with differences in brain asymmetry in areas related to working memory, language, hand control and vision. Some of these brain areas were linked to specific genes. Scientists have long been fascinated by left-handedness.
Sometimes people who are left-handed are called many different things, “Southpaws”, "Lefties", and other simply mean names, like "Weird" or "Strange".
Researchers say the steadily low percentage of lefties "is a result of the balance between cooperation and competition in human evolution." Humans have long had an evolutionary need to cooperate, such as when sharing tools or hunting in groups. And if most people use the same hand, it makes such cooperation easier.
Ethnic differences in handedness are related to geographi- cal differences, with left-handedness generally being more common in White, Asian and Hispanic populations – a differ- ence seen both in the UK, and historically in the United States, where the difference between ethnic groups has grown smaller during the ...
Left-handedness has been discouraged as recently as the mid-20th century. At times, physical restraints have been used, such as tying a child's left hand behind their back.
But handedness has its roots in the brain—right-handed people have left-hemisphere-dominant brains and vice versa—and the lefties who claim Einstein weren't all that far off. While he was certainly right-handed, autopsies suggest his brain didn't reflect the typical left-side dominance in language and speech areas.
However, post-hoc exploration of their and other sets of data has shown that there is an apparent tendency for left-handedness to be more prevalent in the period March-July than in the period August-February.