Skip to main content

What causes some people to be left-handed, and why are fewer people left-handed than right-handed?

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 % of people are right-handed. These theories also try to explain the persistent and continuing presence of a left-handed minority (about 15% 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 and the other allele is a C gene.

 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% chance of being right-handed and a 50% 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 favour 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.



Credits: Nivethithaa
Labels:

Comments

Post a Comment

Popular posts from this blog

WHY ATLANTIC AND PACIFIC OCEAN ARE NOT MIXED?

Nearly 72% of the earth is filled with water and it is present with different names- oceans, seas, rivers. Why are they named differently? There are five oceans namely Artic ocean, Atlantic Ocean, Pacific Ocean, Indian ocean and Antarctic ocean . All the oceans are different in their physical and biological character called ocean clines. When we look at the Atlantic and Pacific Ocean junction, they do not mix. Is there any invisible Wall in between them? Many scientists have conducted research to solve this mystery. The Atlantic and Pacific Ocean have different chemical composition. The salinity of the water in the Atlantic Ocean is five times more than the Pacific Ocean. The density of water is also different, so even marine animals in Atlantic Ocean will not go to the Pacific Ocean. They cannot survive in other oceans. Atlantic and Pacific Ocean meet at Cape Horn. The narrow straight line formed by the water bodies is called Drake Strait. The Pacific Ocean is
Post a Comment
Read more

World’s most Expensive Frog

The Poison Dart frog, which is 6cm long, is the world's most expensive animal. The worth of the frog is Rs 1.5 lakhs. It is expensive because of its poison and color. They are the most brightly colored frogs in the world. It is found in yellow, gold, copper, red, green, blue, golden, or black. Beneath its skin, it keeps its poison. The poison is called batrachotoxin. This type of frog is found in wet, tropical forests of Central and South America, where their diet contributes to the toxins they secrete through their skin. The Golden Poison Dart frog is the most toxic among them. The venom it has is enough to kill 10 grown men. It eats ants and small insects that have toxic chemicals in their bodies. The insects consume toxic plants, and the frog consumes the insects. If a Blue Poison Dart frog is touched, it does not cause death like a Golden Poison Dart frog. Instead, it causes immense pain, cramping, stiffness, serious swelling, nausea, and muscular paralysis.
1 comment
Read more

Blockchain Technology

Do you know who introduced the first Blockchain? Blockchain technology is a revolutionary technology that is popularly known as the Backbone of Digital Cryptocurrencies, which have been generating incredible hype in the last decade. Blockchain was introduced by the unknown persons behind the online cash currency bitcoin, under the pseudonym of Satoshi Nakamoto. Do you know why Blockchain was introduced? Blockchain allows participants of the network to perform mathematical verification and reach a consensus to agree on any particular value. While making a transfer, the sender uses their private key and announces the transaction information over the network. Blockchain technology can be used to create a Permanent, Public, transparent ledger system for compiling data on sales, tracking digital use, and payments to content creators, such as wireless users or musicians.                           Most people who lack familiarity with blockchain confuse it for a bitcoin; however, bitcoin is t
Post a Comment
Read more