Nadene Goldfoot
I'm genetically left-handed from a Jewish family. My brother and I are both left-handed but our parents are both right-handed, so our mother and father must both be carrying the left-handed recessive gene. Also, our paternal 1st cousin is also left-handed, and he was an only child. His father, our father's brother, was right-handed. We Jews are an endogamous people, so this shows how DNA is working.
A recent study has shown that a staggering 30% of Jewish people are left handed. This is a significantly higher percentage than the general population, where only 10-15% of people are left handed. The study did not examine the reasons behind this trend, but it is speculated that it could be due to the high percentage of Jewish people with genetic disorders or disabilities.
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This trend is especially interesting because in many cultures, left handedness is considered to be unlucky or even evil. In some parts of the world, left handed people are forced to use their right hand for everything, even if it is not their natural preference. In Judaism, however, left handedness is not seen as a negative trait. In fact, some of the most famous and respected Jewish figures were left handed, such as Moses, King David, and the prophet Elijah.
Despite the high percentage of left handed Jewish people, there is no definitive answer as to why this trend exists. However, it is clear that left handedness is not seen as a negative trait within Judaism, and that left handed Jewish people have made significant contributions to both their religion and culture.
If both parents of a child are left-handed, there is only a 26% chance of that child being left-handed. A large study of twins from 25,732 families by Medland et al. (2006) indicates that the heritability of handedness is roughly 24%.
Our intelligence is observed. In his book Right-Hand, Left-Hand, Chris McManus of University College London argues that the proportion of left-handers is increasing, and that an above-average quota of high achievers have been left-handed. He says that left-handers' brains are structured in a way that increases their range of abilities, and that the genes that determine left-handedness also govern development of the brain's language centers. Left-handed people differ from right-handers by only one IQ point, which is not noteworthy ...
Left-handers' brains are structured differently from right-handers' in ways that can allow them to process language, spatial relations and emotions in more diverse and potentially creative ways. Also, a slightly larger number of left-handers than right-handers are especially gifted in music and math. A study of musicians in professional orchestras found a significantly greater proportion of talented left-handers, even among those who played instruments that seem designed for right-handers, such as violins. Similarly, studies of adolescents who took tests to assess mathematical giftedness found many more left-handers in the population.
In two studies, Diana Deutsch found that left-handers, particularly those with mixed hand preference, performed significantly better than right-handers in musical memory tasks. There are also handedness differences in perception of musical patterns. Left-handers as a group differ from right-handers, and are more heterogeneous than right-handers, in perception of certain stereo illusions, such as the octave illusion, the scale illusion, and the glissando illusion.
Only around 30% of left-handers are not left-hemisphere dominant for language. Some of those have reversed brain organisation, where the verbal processing takes place in the right-hemisphere and visuospatial processing is dominant to the left hemisphere. Others have more ambiguous bilateral organisation, where both hemispheres do parts of typically lateralised functions. When tasks investigating lateralisation are averaged across a group of left-handers, the overall effect is that left-handers show the same pattern of data as right-handers, but with a reduced asymmetry. This finding is likely due to the small proportion of left-handers who have atypical brain organisation.
Left-handed quarterbacks were relatively prominent in the NFL between the 1970s and the 2000s, but became mostly absent from the league after 2010. The most successful have been Pro Football Hall of Fame inductees Steve Young and Ken Stabler, 1988 Most Valuable Player Boomer Esiason, and Pro Bowl selections Frankie Albert, Mark Brunell, and Michael Vick. Tua Tagovailoa, who was drafted in 2020, is currently the NFL's only left-handed quarterback.
Interactive sports such as table tennis, badminton and cricket have an overrepresentation of left-handedness, while non-interactive sports such as swimming show no overrepresentation. Smaller physical distance between participants increases the overrepresentation. In fencing, about half the participants are left-handed. The term southpaw is sometimes used to refer to a left-handed individual, especially in baseball and boxing.studies suggest that right handed male athletes tend to be statistically taller and heavier than left handed ones.
However, left-handed people have an advantage in sports that involves aiming at a target in an area of an opponent's control, as their opponents are more accustomed to the right-handed majority. As a result, they are over-represented in baseball, tennis, fencing, cricket, boxing, and mixed martial arts (MMA).
Our health was observed. Studies have found a positive correlation between left-handedness and several specific physical and mental disorders and health problems. For example:
Lower-birth-weight and complications at birth are positively correlated with left-handedness.
A variety of neuropsychiatric and developmental disorders like autism spectrum disorders, depression, bipolar disorder, anxiety disorders, schizophrenia, and alcoholism have been associated with left- and mixed-handedness.
A 2012 study showed that nearly 40% of children with cerebral palsy were left-handed, while another study demonstrated that left-handedness was associated with a 62% increased risk of Parkinson's disease in women, but not in men. Another study suggests that the risk of developing multiple sclerosis increases for left-handed women, but the effect is unknown for men at this point.
Left-handed women may have a higher risk of breast cancer than right-handed women and the effect is greater in post-menopausal women.
At least one study maintains that left-handers are more likely to suffer from heart disease, and are more likely to have reduced longevity from cardiovascular causes.
Left-handers may be more likely to suffer bone fractures.
One systematic review concluded: "Left-handers showed no systematic tendency to suffer from disorders of the immune system".
As handedness is a highly heritable trait associated with various medical conditions, and because many of these conditions could have presented a Darwinian fitness challenge in ancestral populations, this indicates left-handedness may have previously been rarer than it currently is, due to natural selection. However, on average,
In a 2014 study published by the National Bureau of Economic Research, Harvard economist Joshua Goodman finds that left-handed people earn 10 to 12 percent less over the course of their lives than right-handed people. Goodman attributes this disparity to higher rates of emotional and behavioral problems in left-handed people.
Two theoretical single-gene models have been proposed to explain the patterns of inheritance of handedness, by Marian Annett of the University of Leicester, and by Chris McManus of UCL. However, growing evidence from linkage and genome-wide association studies suggests that genetic variance in handedness cannot be explained by a single genetic locus. From these studies, McManus et al. now conclude that handedness is polygenic and estimate that at least 40 loci contribute to the trait.Brandler et al. performed a genome-wide association study for a measure of relative hand skill and found that genes involved in the determination of left-right asymmetry in the body play a key role in handedness. Brandler and Paracchini suggest the same mechanisms that determine left-right asymmetry in the body (e.g. nodal signaling and ciliogenesis) also play a role in the development of brain asymmetry (handedness being a reflection of brain asymmetry for motor function).
In 2019, Wiberg et al. performed a genome-wide association study and found that handedness was significantly associated with four loci, three of them in genes encoding proteins involved in brain development.
- Researchers still don’t understand why around 10 per cent of the population turn out to be left-handed.
- Most children have a preference for using one hand or the other by the age of about 18 months, and are definitely right or left-handed by about the age of three.
- If your child is naturally left-handed, don’t try to force them into using their right hand. I was 6 years old, a 1st grader in 1940. Teachers did try to change my preferred left hand, but I couldn't stand it. I, a little different than my brother and cousin, write as an upside down writer as well, with my left hand curled with my wrist being above my writing.
In a study from 1975 on 7688 children in US grades 1-6, Left handers comprised 9.6% of the sample, with 10.5% of male children and 8.7% of female children being left-handed. Handedness is often defined by one's writing hand, as it is fairly common for people to prefer to do some tasks with each hand. There are examples of true ambidexterity (equal preference of either hand), but it is rare—most people prefer using one hand for most purposes.
Most of the current research suggests that left-handedness has an epigenetic marker—a combination of genetics, biology and the environment.
Because the vast majority of the population is right-handed, many devices are designed for use by right-handed people, making their use by left-handed people more difficult. In many countries, left-handed people are or were required to write with their right hands. Left-handed people are also more prone to certain health problems. As the right hand is controlled by the left hemisphere (and the left hand is controlled by the right hemisphere) most people are, therefore right-handed. The theory depends on left-handed people having a reversed organisation. However, the majority of left-handers have been found to have left-hemisphere language dominance—just like right-handers.
