According to conventional wisdom, babies are born with the ability to be right or left handed. But it turns out that handedness is decided well before birth.
New research from scientists at the Universities of Oxford, St Andrews, Bristol and the Max Plank Institute in Nijmegen, the Netherlands reveals a network of genes that are likely associated with establishing a left- or right-handed bias in embryos. Only about 10% of humans are left-handed, and previous theories focused on everything from which thumb babies start sucking in the womb, to the role of hormones like testosterone .
But by conducting a genome-wide association study — in which scientists compare a wide array of genetic differences in right- and left-handed people — in four different population groups, the research team found that variants in the gene PCSK6 contributes to handedness determination. This gene is intimately involved in turning a spherical ball of equally oriented cells into an embryo that has discernible left and right sides. Defects in the gene in mice, for example, cause organs to be misplaced, such as having the heart develop on the right side and the liver on the left side. These influences also appear to determine handedness, or relative dexterity, at a level greater than would occur by mere chance.
Although the findings, published in the journal PLOS Genetics, bolster the argument for a genetic component to handedness, the researchers stress that genes may only be part of what determines right- or left-handedness. There is equally solid evidence supporting the role that training and behavior have on whether someone favors the right or left hand, for example, so understanding how genes influence the asymmetrical development of body and brain provides a broader appreciation of how both nature and nurture contribute to dexterity.