We measured the lengths of some parts of the right and left hemispheres (HEs) in 70 formalin-fixed brains and on 15 computed tomography/magnetic resonance imaging (CT/MRI) images (7 left-handed and 8 right-handed cases) to clarify the morphological changes indicating which HE developed earlier and handedness. In many cases of the fixed brains, 1) the distance from the frontal pole to the occipital pole was longer in the left HE than in the right HE, 2) the distance from the middle plane to the lateral-most portion of the HE was wider in the right HE than in the left HE, 3) the left occipital pole elongated more posteriorly and covered the right occipital pole, and 4) the volume of each HE was nearly the same. The results indicate that the left HE develops and grows slightly earlier in the larger semi-cranium (half of the cranium) than the right HE which develops later in the smaller semi-cranium. The whole brain was more spherical in the female cases than in the male cases. The morphological changes in both HEs for handedness were not evident on the CT/MRI images.
The study of the biology of human language, biolinguistics, has been fruitfully investigated over the last sixty years. Many important insights have been gained into the questions of what language is (mechanisms and functions), how language develops (growth of language), and how language evolves in the species. Principles of symmetry have often helped to unify areas of the natural sciences such as physics, chemistry and biology. The application of symmetry to the kinship system of the Warlpiri aborigines of Australia is examined to demonstrate how symmetry illuminates the intersection of language and other cognitive systems.