What determines whether you are left or right handed?

Answer 1

Scientists aren't entirely sure, although they're pretty positive it's genetic. For a long time, a prevailing theory was that handedness is determined by gene expression in the left or right hemisphere of the brain. However, newer research suggests that even before the motor cortex is developed, an early asymmetry in the spinal cord is actually what determines right or left handedness.

Answer 2

Genetics!

Answer 3

Researchers who study human hand preference agree that the side of the preferred hand (right versus left) is produced by biological and, most likely, genetic causes. The two most widely published genetic theories of human hand preference argue that evolutionary natural selection produced a majority of individuals with speech and language control in the left hemisphere of the brain. Because the left hemisphere also controls the movements of the right hand--and notably the movements needed to produce written language--millennia of evolutionary development resulted in a population of humans that is biased genetically toward individuals with left hemisphere speech/language and right-hand preference. Approximately 85 percent of people are right-handed. These theories also try to explain the persistent and continuing presence of a left-handed minority (about 15 percent of humans).

The genetic proposal to explain hand preference states that there are two alleles, or two manifestations of a gene at the same genetic location, that are associated with handedness. One of these alleles is a D gene (for dextral, meaning ¿right¿) and the other allele is a C gene (for ¿chance¿). The D gene is more frequent in the population and is more likely to occur as part of the genetic heritage of an individual. It is the D gene that promotes right-hand preference in the majority of humans. The C gene is less likely to occur within the gene pool, but when it is present, the hand preference of the individual with the C gene is determined randomly. Individuals with the C gene will have a 50 percent chance of being right-handed and a 50 percent chance of being left-handed.

These theories of hand preference causation are intriguing because they can account for the fact that the side of hand preference of individuals with the C gene (most left-handers and some right-handers) can be influenced by external cultural and societal pressures, a phenomenon that researchers have documented. These theories can also explain the presence of right-handed children in families with left-handed parents and the presence of left-handed children in families with right-handed parents. If the familial genetic pool contains C genes, then hand preference becomes amenable to chance influences, including the pressures of familial training and other environmental interventions that favor the use of one hand over the other. The proposed genetic locus that determines hand preference contains an allele from each parent, and the various possible genetic combinations are DD individuals who are strongly right-handed, DC individuals who are also mostly right-handed, and CC individuals who are either right-handed or left-handed. These genetic combinations leave us with an overwhelming majority of human right-handers and a small, but persistently occurring, minority of left-handers.

Answer 4

most likely genetic and whichever one of your parents has the dominant gene gives you what hand you will be while the recessive trait or gene wont give you that parents right or left handed ability and for some they are able to be born with being able to use both hands

Answer 5

It’s long been assumed that gene activity in the brain, depending on which hemisphere showed the most activity, defines whether or not you were left or right-handed.

The majority of the population (an estimated 70 - 90%) of us are right-handed, which takes us to the question of why some of us are left-handed?

It used to be that being left-handed was not considered socially unacceptable and even in extreme cases being a sign of evil. Many people throughout the ages were forced to learn how to write with their right hands, even though their natural deference was to be left-handed.

Recently an eLife journal study, concluded that your left- or right-handedness is actually integrated in your biological workings, these are preset, before you wre even born. That birth 'pre-set' emerges in the form of a particular hubbub of gene activity in the spine, not your brain.

Answer 6

Scientists aren't entirely sure, although they're pretty positive it's genetic. For a long time, a prevailing theory was that handedness is determined by gene expression in the left or right hemisphere of the brain. However, newer research suggests that even before the motor cortex is developed, an early asymmetry in the spinal cord is actually what determines right or left handedness.

Answer 7

This is a debate which has been going on for thousands of years. Definitely genetics has a major role to play as some children have a tendency to use their left hand primarily from early years. They are natural lefties and their numbers are small when one looks at human population. Majority of the people are right handed. Having said that , there are so many parents who force their kids to use more of their right hand from an early age when they spot that there kid is a lefty and in the process because of the environmental pressure, the poor chap who was actually a left by disposition, turns out to be righty or at best he becomes ambidextrous.

One more observation is pertinent here that people who are lefty are generally more creative because they use more of the right side of the brain which is more concerned with intuition, creativity and arts.

Ideally I think that one should not interfere with the natural selection in this regard and let them be lefty. After all it is the differences in the human race which makes it exciting !!

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Answer 8

Handedness is largely determined by genetics, with around 25% of it influenced by genetic factors. Hormonal exposure in the womb, specifically testosterone levels, also plays a role in determining handedness. However, some environmental factors and learned behaviors can influence hand preference as well.

Answer 9

Cuando el hemisferio izquierdo es el dominante, la mayoría de las órdenes están destinadas a la parte derecha del cuerpo, por eso se es diestro. Por el contrario, cuando el hemisferio derecho es el dominante, la mayoría de las órdenes están destinadas a la parte izquierda, por eso se es zurdo, o quizá también puede ser la genética de tal familiar.

Answer 10

Traditionally a balance was used to measure mass. Objects of known or accepted mass was balanced against another object of unknown mass. When the balance was level the two pans had the same mass. The term balance or scales is still used even though there is no balance used. The scales were the pans that the objects sat on.Now electronic balances are used that gauge the mass of the objects. While you can measure mass with a spring loaded scale, it is less accurate than a balance as it relies on a spring loaded to a specific acceleration of gravity for any given mass. A change in altitude will change the results given on the scale, due to the actual change in gravitational force (it is small at only about 0.031% error for every kilometer increase in altitude)*. A balance would experience no such change as the mass of an unknown quantity is compared to the mass of a known quantity, thus negating any effects of gravity.Another instrument that measures mass is an inertial balance. An inertial balance doesn't require gravity to work, so it can be used in space. It measures the mass of an object by attaching it to a spring and seeing how it affects the spring's period of oscillation.Very tiny masses can be measured directly (using a "massometer"). But we normally use scales, which measure weight, which is directly proportional to mass (a property of matter equal to its resistance to a change in speed or direction of travel). The mass of an object is the same everywhere in the universe. Its weight, however, changes depending upon its location: a Bowling ball has greater weight on the surface of the Earth than it does on the Moon. Great confusion arises when people interchange units of weight with units of mass. Scientists, particularly physicists, are very careful about not using the terms interchangeably, but regular folks have no choice for practical applications. For example, when you weigh a regulation ten-pin bowling ball, the scale will tell you it "weighs" between 4 and 7 (3.63 to 7.27 actually) kilograms, even though the kilogram is, technically speaking, a unit of mass, not weight.You can also measure the mass of an object using a scale, as long as you factor in the gravitational constant (G). For instance, in an environment with only 1/2 the gravity of That on earth, you would have to double the weight displayed on the scale to determine the actual mass. As an example, 10Kg of lead in a 0.5G environment would only "weigh" 5Kg on a scale...half as much as on earth, even though its mass is unchanged.