What Makes Us Right or Left Handed?

The mystery of handedness, or why individuals tend to prefer one hand over the other, has intrigued researchers and scientists for centuries. A glance at your surroundings reveals a world designed predominantly for right-handed people, from scissors and can openers to computer mice and guitars. So, why is it that about 90% of people are right-handed while the remaining 10% are left-handed? This article seeks to provide insights into the fascinating world of handedness, delving into the science and research behind why some of us are right-handed, and others left-handed.

The Science of Handedness

Handedness, in its most basic definition, refers to an individual's natural preference for using one hand over the other. It is a complex trait that appears to be determined by a variety of factors, including genetics, biology, and possibly even the environment.

Genetic Factors

Early theories about handedness proposed a single gene model with two alleles, one for right-handedness and one for left-handedness. However, modern scientific understanding has moved beyond this simplistic model, suggesting instead that multiple genes could be involved. This complex genetic foundation is likely why we see a diverse spectrum of handedness in humans, not just a simple left-right divide. Although the precise genetic mechanisms remain unclear, studies suggest that genetics account for about 25% of the determination of handedness.

Biological Factors

In addition to genetics, biological factors also contribute to the development of handedness. Some theories suggest that handedness is determined by the asymmetry in the human brain. The human brain is divided into two hemispheres: the left and the right, each controlling different functions. Notably, the left hemisphere of the brain, which controls the right hand, is generally responsible for tasks related to language and logic, while the right hemisphere, controlling the left hand, is often linked with spatial and creative tasks.

However, this is not a strict rule, and there is significant overlap and cooperation between the two hemispheres. In about 90% of right-handed individuals, language is lateralized to the left hemisphere. But, intriguingly, in left-handed people, about 70% also have their language lateralized to the left hemisphere, and 30% either to the right hemisphere or distributed evenly. This asymmetrical brain function might have a role in determining whether we become right or left-handed.

Environmental Factors

Research also suggests that environmental factors can influence handedness. For instance, one theory known as the "Barker Hypothesis" proposes that conditions in the womb, such as the position of the fetus, can influence which hand becomes dominant. Further support for environmental factors comes from studies of "culturally driven handedness," where societal pressure and cultural norms may affect an individual's dominant hand, especially in societies where being right-handed is strongly favored.