Is handedness determined by genetics?
Handedness is a complex trait influenced by a combination of genetic factors and environmental influences, rather than a single gene.
Overview
Handedness, or hand preference, is the tendency to be more skilled and comfortable using one hand instead of the other for tasks such as writing and throwing a ball. While percentages vary worldwide, in Western countries, 85 to 90 percent of people are right-handed, while 10 to 15 percent are left-handed. Mixed-handedness and ambidextrousness are considered uncommon.
Development and Biological Basis
Hand preference typically becomes apparent in early childhood and remains consistent throughout life. While the exact biological basis is not fully understood, it is likely part of the developmental process that differentiates the right and left sides of the body, known as right-left asymmetry. This is related to differences between the right and left hemispheres of the brain, where the right hemisphere controls movement on the left side of the body and the left hemisphere controls movement on the right side.
Genetic and Environmental Factors
Early theories suggested a single gene controlled handedness, but modern research indicates a more complex picture:
- Multiple Genes: Studies suggest that up to 40 genes may contribute to this trait, each with a weak individual effect. Together, they play a significant role in establishing the body's overall right-left asymmetry.
- Inheritance Patterns: Handedness does not follow a simple pattern of inheritance. While children of left-handed parents are more likely to be left-handed, most children of left-handed parents are still right-handed.
- Twin Studies: Identical twins are more likely than non-identical twins or other siblings to share the same hand preference, though many twins still exhibit opposite preferences.
- External Influences: Research suggests that the prenatal environment and cultural influences also play a role in determining handedness.