The Right Shift Theory
The Right Shift Theory
In 1972, Marian Annett of the University of Leicester UK proposed a theory that came to be known as the Right Shift Theory. She believed that as humans evolved, all of the major functions of the brain, such as speech, shifted to being controlled and centered in the left hemisphere of the brain, which controls the right side of the body naturally. By shifting important functions to the left, a bias for the right hand would be created. This lateralization and biased, according to the theory, is controlled by a gene, or a set of genes. More recent studies, specifically those of Dr. Amar J.S. Klar, agree with Annett on the assumption that the right-handed bias found in the population is caused by a set of genes. 20% of people do not inherit these genes, says Klar, and because of this they have an even chance of being either right or left handed. This theory would then match up with the 10% average of left-handed people. If roughly half of the individuals that did not inherit the right bias gene became left handed, and half became right handed, then half of that 20% would agree with the recorded 10% of the population. A genetic approach to the modern Right Shift Theory is best explained by two alleles. One, the D gene, stands for dextral and is more frequent in the population. While the other, the C gene, stands for chance and when it is present, the handedness of the individual becomes highly susceptible to outside environmental factors. When the alleles are combined, a DD combination would yield a strongly right biased individual. A DC combination of alleles would create an individual who is mostly right handed; and a person who possesses a CC gene has a chance of developing a left handed bias. This genetic proposal accounts for the small but persistent survival of left-handed people.
Mcmanus Model (Lateralization)
The Mcmanus model is based on the idea of brain lateralization. Instead of proposing that specific genes decide handedness,
In 1972, Marian Annett of the University of Leicester UK proposed a theory that came to be known as the Right Shift Theory. She believed that as humans evolved, all of the major functions of the brain, such as speech, shifted to being controlled and centered in the left hemisphere of the brain, which controls the right side of the body naturally. By shifting important functions to the left, a bias for the right hand would be created. This lateralization and biased, according to the theory, is controlled by a gene, or a set of genes. More recent studies, specifically those of Dr. Amar J.S. Klar, agree with Annett on the assumption that the right-handed bias found in the population is caused by a set of genes. 20% of people do not inherit these genes, says Klar, and because of this they have an even chance of being either right or left handed. This theory would then match up with the 10% average of left-handed people. If roughly half of the individuals that did not inherit the right bias gene became left handed, and half became right handed, then half of that 20% would agree with the recorded 10% of the population. A genetic approach to the modern Right Shift Theory is best explained by two alleles. One, the D gene, stands for dextral and is more frequent in the population. While the other, the C gene, stands for chance and when it is present, the handedness of the individual becomes highly susceptible to outside environmental factors. When the alleles are combined, a DD combination would yield a strongly right biased individual. A DC combination of alleles would create an individual who is mostly right handed; and a person who possesses a CC gene has a chance of developing a left handed bias. This genetic proposal accounts for the small but persistent survival of left-handed people.
Mcmanus Model (Lateralization)
The Mcmanus model is based on the idea of brain lateralization. Instead of proposing that specific genes decide handedness,