Lefties are a minority in the "world of right-handed" and attitude to them has always been the same negative as any minority.This is partly explained by practical reasons: the left-hander is not easy to cope with work tools, designed for right-handers.For example, a farmer-lefty could confuse flails threshing or mowing hurt someone spit.Such a "clumsy" make a man an outcast in a peasant community.

was equally uncompromising attitude towards left-handedness in the noble families.Babies left-handed even tied his left hand to the body to enjoy the right to teach.Especially strongly retrained girls, because girls are not considered to be left-handed enviable bride.

In today's society there is no such rejection lefties, but these people are still not easy to live with.Even now, many tools from tin knives and ending wi
th musical instruments, "incarcerated" under the right-handed people.

Genetic and compensatory mechanisms left-handedness



innate left-handedness is not in doubt.The only exceptions are cases of compensatory left-handedness when this phenomenon is caused by the limited mobility of his right hand as a result of injury or illness.Another option pathological compensatory left-handedness - inhibition activity of the left hemisphere as a result of birth trauma.Then the right hemisphere controls the left hand necessarily have to take the lead.

Medical statistics show that transmission of hereditary characteristics: the probability of a child left-handed left-handed parents are much higher.This is true even in cases where parents in childhood transitioned to the use of his right hand, which eliminates the mechanism of imitation.

no "left-handed gene" to date not revealed, but the English researcher M. Annette has put forward the idea of ​​"the right translation of the gene," which makes the leading hemisphere and the left, respectively, right hand.If such a person did not get the gene, leading hemisphere is determined by a random, they can be and left.And it may happen that the leading hemisphere is not at all - people will equally own two hands (these people are called ambidexterity).However, more often than not they hold hands equally well and is equally bad.

Alternative explanations



Some researchers have linked left-handedness with the terms of fetal development.For example, an American neurologist N. Gershvind as a possible cause described elevated levels of testosterone in the mother during pregnancy.The excess of this hormone inhibits the development of the left hemisphere of the fetus, and it can not be a leader.But the scientist is stipulated that such an effect occurs only in male embryos and left-handers and girls are born.

Russian biologist Vladimir Geodakyan connects left-handedness with the evolutionary history of the brain.The left hemisphere - the younger the evolutionary standpoint, therefore, it is more vulnerable.It is the first to suffer from adverse environmental conditions and stress experienced by the mother during pregnancy, and other factors that adversely affect the fetus."Victim" left brain is forced to give up the lead right.

There is a hypothesis linking handedness with fetal ultrasound.However, the research on which it is based, can not be considered perfect: the statistical sample was insufficient.Besides, it does not explain why lefties were born long before the invention of ultrasound diagnostics.

Thus, there are different theories of origin of left-handedness, but the consensus among scientists on this issue no.