Handedness and brain asymmetry are widely regarded as unique to humans, and associated with complementary functions such as a left-brain specialization for language and logic and a right-brain specialization for creativity and intuition.
In fact, asymmetries are widespread among animals, and support the gradual evolution of asymmetrical functions such as language and tool use. Handedness and brain asymmetry are inborn and under partial genetic control, although the gene or genes responsible are not well established. Cognitive and emotional difficulties are sometimes associated with departures from the “norm” of right-handedness and left-brain language dominance, more often with the absence of these asymmetries than their reversal.
One myth that persists even in some scientific circles is that asymmetry is uniquely human. Left–right asymmetries of brain and behavior are now known to be widespread among both vertebrates and invertebrates, and can arise through a number of genetic, epigenetic, or neural mechanisms. Many of these asymmetries parallel those in humans, or can be seen as evolutionary precursors. A strong left-hemispheric bias for action dynamics in marine mammals and in some primates and the left-hemisphere action biases in humans, perhaps including gesture, speech, and tool use, may derive from a common precursor.
Read the full, original article: Left Brain, Right Brain: Facts and Fantasies
- Genetic expression in the human brain: The challenge of large numbers, Genetic Literacy Project
- New study shows dexterity largely determined by genetics, US News & World Report