Scientific minds recently provided an explanation on why some people are left-handed, while others are right-handed. In some cases, people may be ambidextrous, able to use the right and left hands equally well.
A new study conducted by a team of researchers from Ruhr-Universität Bochum, in collaboration with the Max Planck Institute for Psycholinguistics in the Netherlands, as well as the Dutch Radboud University and the South-African Wellenberg Research Centre at Stellenbosch University, pointed out that the signs may begin in the mother’s womb. A report of the study was published in the journal eLife.
The findings underscored that unborn children tend to make asymmetric movements with their hands as early as 12 weeks gestation. Moreover, the study noted that it is not the brain that determines if people are right or left-handed, but the spinal cord. The biopsychologists highlighted that gene activity in the spinal cord is asymmetrical as early as being in the womb.
Clarifying Notions About a Person’s Handedness
Most people may not be interested to know why a person is left-handed or right-handed. Numerous notions have been passed on from one generation to another citing the factors that could be responsible for a person’s handedness.
For years, the differences in gene activity of the left and right hemispheres were believed to be responsible for a person’s handedness. The new research offered an explanation that it is the spinal cord – the vital structure between the body and the brain – that is a key determinant if people are right or left-handed – not the brain.
The researchers analyzed gene expression in the spinal cord during pregnant subjects’ eighth to 12th week of pregnancy. They found marked right-left differences in the eighth week – in the spinal cord segments controlling the movements of arms and legs. From the 13th week of pregnancy, unborn children’s preference to suck either their left or right thumb was observed.
Influence of Environmental Factors
Epigenetic factors, to the researchers’ minds, were regarded as the root cause of asymmetric gene activity. A huge percentage of populations are right-handed. However, as a researcher from the Max Planck Institute cited, genetic and environmental factors may offer alternative paths of development, such as left-handedness or two-handedness.
The finding that majority of human fetuses move their right arms more than their left arms as early as eight weeks post conception was also published in the journal Biological Psychiatry. It deduced that because nerve fibre tracts are still descending from the forebrain at that life stage, spinal-muscular asymmetries are more likely to play an important developmental role. Indeed, handedness remains a mystery, including how certain genes that exhibit the largest left-right differences in the embryos may be involved in the risk of schizophrenia.