Handedness is an asymmetry arising due to left-right differences in the development of nervous system. Evidences suggest that a human embryo of eight weeks is able to move its right arm more than the left arm.
Well, if you know something about neurologic development in-utero, you must know that at eight weeks signals are not transmitted from the brain yet. Instead the signals travel from the spinal cord.
The left side of the cord matures faster than the right cord. This means the genes that control growth and development are activated faster on the left cord than the right one. In the hindbrain, it is the other way around.
- Jaskunwar Singh