I am looking for a scientific reason be it biological phenomenon, genetic order etc which can explain how and why some people become left-handed?

in 2007, researchers discovered that specific alleles of at least one of three single-nucleotide polymorphisms upstream of the already known LRRTM1 gene, were linked to left-handedness another theory is exposure to higher rates of testosterone before birth can lead to a left-handed child.This is the Geschwind theory, named after the neurologist who proposed it, Norman Geschwind. It suggests that variations in levels of testosterone during pregnancy shape the development of the fetal brain. Testosterone suppresses the growth of the left cerebral hemisphere and so more neurons migrate to the right hemisphere. The highly developed right hemisphere is now better suited to function as the center of language and handedness. The fetus is more likely to become left-handed, since the right hemisphere controls the left half of the body. The theory goes on to tie the exposure to higher levels of testosterone and the resultant right-hemisphere dominance to an increased risk of auto-immune disorders, learning disorders, dyslexia, and stuttering, as well as increased spatial ability. regards source is wikipedia

I am a left handed girl.And the reason is family.We are ''lefties''.

Anyways the reasons why some people are left handed are not clear,but they seem to depend on a mixture of genetic and environmental factors.
left handedness seem to run in families,but it also appears in families with where no immediate member is left-handed.Some theoretical environmental reasons for left handedness are birth trauma,exposure to high levels of testosterone in the womb and physical conditioning.

only 4% of the population is left handed.

One particular theory is something related to two halves of brain.the left half and the right half.each of which functions differently.medical science believes that left half of the brain predominates the right half.the stem of this theory is the fact that nerves from the brain cross over at neck-level to the opposite side of the body.and nerves from the other side of the brain reciprocate.the end result is that the opposite sides of the body are supplied by the opposite of the brain.

The predominant left half of the brain,which graciously supplies the right half of the body,theoretically renders it more skillful in reading,writing,speaking,and working and makes most people right handed.''lefties'' however are the product of an inversion,whereas the right half of the brain predominates,and they work best with the left side of their bodies.

Theory number 2 trickles down to the asymmetrical nature of the body.examples of the asymmetry,which flows from head to the toe,are that the right side of our faces differs slightly from the left,that our legs differ in strength or that our feet vary in size.one aspect of asymmetry is that for most people right hand is stronger than the left.

Lefties are athletically inclined,think more quickly,they have twice the problem solving skills and higher IQ.People who use their left hand to write but favor the right side in every thing else scored the same as ''true''right handed people.

you can check this link for detailed answer.

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

Our society is just for right handed people.Basic things like scissors,doorknobs,locks,screwdrivers,automobiles, buttons on clothing and musical instruments are just for 96%of the population.

Nobody cares about us.In exams It is we who suffer with those damned right arm chairs.

Why the heart of some people is found on the right side?
Same is the reason for the above question.

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Fixed signs.

i m a left handed boy.....it means my right brain is more efficient.....if it is so...then it would also has impacts on career fields.....

i m still doing electrical engineering and it involve circuits and mathematics....but i want to do css....can any one tell me what is better for me in context ov my mental approach..??

Yes some people has heart on right side and this is called Dextrocardia.in this condition heart is placed on the right side of the thorax.first revealed by Leonardo Da Vinci.Dextrocardia is commonly associated with sever defects of the heart.
one condition is Dextrocardia Situs Inversus.
It refers to the heart being a mirror image situated on the right side.its a complete normal condition with not sever problems afflicting those with heart on right side.but yes there are some problems such as they are prone to number of bowl,esophagus,bronchial,and cardiac problems.some can be life threatening if left unchecked.but these can happen to people with heart on left side as well.
So location doesn't matter here.whether its left or right heart should be healthy and without faults like holes in the upper or lower septum.It is called ventricular septal defect.similarly some diseases are complex congenital heart defects.these are extremely risky situations and the patients need constant diagnoses.so there are very complex heart problems out there and Dextrocardia has nothing to do with these things.its just a changed position of your heart.you need not to put it on the left side.

You are in excellent field bro.My twin bro is also lefty like me.And he too is electrical engineer.He has never complained that he faces difficulties with mathematics and circuits etc.in fact he is excellent in his field.topped his FSC and going great in his masters in electrical engineering as well.with planing to do his PH.d in it.i would say that lefties are excellent in this field if we only scrutinize their mental abilities.though physically they suffer but what's the use of conditioning then.you are not a sudden lefty its your style since childhood.In adult age we face no more troubles.in electrical or mechanical field though you have to work with hands but brain is also used extensively and in that area you are not far behind these righties.You are in good and suitable field bro.
But as this world is only for right hand people we left hand minority will have some disadvantages for ever.
And yes you must have faced some difficulties in operating things like cameras,car openers,PC keyboard and mouse.pencil sharpeners,rulers etc.
similarly you must have difficulty in operating gun.if you fire gun with your left hand then the hot shell cases will eject to your side.But with little adjustment you can avoid being hit by a shell on your eye.so its not a big issue.you are an engineer not a killer.

But no need to worry all you lefties becaz lefties brains are just special with increased range of abilities they are multitaskers.right side of the brain is responsible for creative thought.They are excellent batsman and tennis players and fast bowlers.if they are good with sports material then what's the big deal if you are operating machines.

@ gul niazi

I will be highly thankful to you if you can provide me the reference about the effect of testosterone in the right or left hand conquest of an individual?

Well bro first of all Its not a final word that testosterone is responsible for left-handedness but since its the male population which is most vulnerable to this left-handedness so scientists say that may be Its male sex hormone called testosterone which is responsible for it.But still its just theories nothing concrete is established yet.

you can check this link as well.

Understanding Genetics: Human Health and the Genome

And this one is for left handed guys only.

Current research into lefthandedness | Anything Left-Handed

These might be the secondary reasons but there is something with the genes prior to birth which determines whether a child would grow up to become a right-handed or left-handed person.

The link you provided says that 15% of world population is left-handed. Please confirm.

This seems to be an agreeable answer of the above question.

I think it would be an altruistic statement to assert this. If it was so, many people in the field of physiology would have attempted to find a deliberate way to become left-handed. Still, it's quite predominant to say that left-handed people possess higher problem solving skills. Though, exceptions are everywhere.

I think left-handed people use their right hand just like right-handed people in everything except writing. All the objects mentioned above can still work in the same if operated by a left-handed person. There isn't prejudicial element in it.

Ohh dear Gul, let me give you a happy news! FPSC does offer chairs with arms on their left side for CSS candidates at their headquarters. If you are lucky enough to get your exam center at FPSC Headquarters (F-5 Agha Khan Road, Near Marriott), you will save yourself of some discomfort.

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Verily, His command, when He intends a thing, is only that He says "Be!" - and it is! (Al-Quran)

You have terribly dissected my posts bro.any ways I am not here for debate.If you are insisting on genes then maybe you are right but that too will not be hundred percent confirmed.

Yeah i know i have said 4 percent and in link it was 15 percent.but this too is not confirmed.some say 10 percent some say 11 percent.dont know exact figure myself.
if you know then tell me too.

You are much informed then me in fact.good for you.best of luck.

I have not said that we are victims of society's high handedness.its just things don't fit us properly.I have just said this.

Well my center will be Lahore.let's see what's there for me.but ab aadat ho gai hai in damned chairs ko use karney ki..so no problem.