Why is it that some people are left-handed while others are right-handed?

Gnomon

Scientists genuinely don't know the answer to this question, Candylicious, as the following quotes from Encyclopaedia Britannica (1998) show: "There is no extensive agreement on the origin of manual preferences." "Recent research, however, suggests that right-handedness and left-handedness are not genetically encoded within the body's genes but rather are coded in the spatial structure of ovarian cells. Other scientists believe handedness is not biologically determined at all, but is a factor of the environment." "Neither of these bits of evidence shows conclusively, however, that the cortical organization a person inherits is responsible for his hand preference." Aug 01 06, 4:40 AM

zbeckabee

Scientists have been studying "handedness" (i.e., which hand people tend to use for writing and other precise motor skills) for about 160 years, and they still haven't discovered what causes someone to prefer one hand over the other. Most people in the world are right-handed -- only 5% to 30% are left-handed. No one's sure if left-handedness is genetic, a learned behavior, caused by prenatal or birth trauma, or if it's some combination of these factors. http://ask.yahoo.com/20020628.html Aug 01 06, 8:20 AM

debbie482

Just for the record Im ledt handed I have 4 children all right handed and my husband is right handed Aug 01 06, 8:44 AM

jules_babe

I'm right handed, but play football with my left foot, golf right handed, and cricket left handed. Aug 01 06, 9:22 AM

Blue1597

My father did everything left-handed for everything except writing. In school he was hit with a ruler until he learned to write with his right. Of his 3 daughters I am the only one also left-handed, however, my brain appears to be somewhat cross-wired like jules_babe's. I throw a ball left handed but a frisby right handed. I golf left handed but hit a baseball and play guitar righthanded. LOL Aug 01 06, 10:59 AM

CaroSun

I learned in school that being right-handed is normal for human beings and being left-handed is a handicap. It has something to do with our brain. I'm sorry, I don't have a reference to back this up. Aug 01 06, 11:02 AM

debbie482

I write left handed but bat (baseball) right hande and use right handed scissors Aug 01 06, 11:08 AM

Allergic2Life

I have heard that the Romans required their soldiers to use their swords with their right hands, this caused the predominance of right handed people. Aug 01 06, 11:17 AM

Baloo55th

I rather think that's one of those legends. However, if someone has proved that the majority of the world's population is descended from Roman soldiers, I'll perhaps change my mind. In fact, the prevalence of right-handedness predates the Roman army. They can tell by the way that some sorts of stone tools are made or worn which hand was involved, and the majority show as right-handed. http://en.wikipedia.org/wiki/Oldowan or more academically, http://bioweb.usc.edu/courses/2001-spring/documents/core103-032701.pdf. Page 1, fortunately. This refers to the dwellers in the Olduvai Gorge area, who are believed to be ancestral to modern humans. There was a predominance in the stone tools of 57% right to 43% left. Righthandedness (and lefthandedness) seem to be human characteristics, and chimpanzees show no preference for either hand normally. Aug 01 06, 1:14 PM

Baloo55th

A slightly irrelevant point. When teaching the recorder to left-handed pupils, I find they almost always put the right hand at the top and the left hand at the bottom. When asked why, they claim it's because they are left-handed. On the recorder you use both hands for virtually the same job, and the instrument is designed for the right hand to be at the bottom (it's to do with the double holes on the bottom two finger positions). Aug 01 06, 1:19 PM

Gnomon

I tried out a flint scraper, a tool for removing meat from an animal hide, which was made by Neanderthals in England in 350,000 BC. (This was at the British Museum). It was quite clearly designed to be used in the right hand. Aug 01 06, 2:12 PM