Brain asymmetry in the white matter making and globularity

Area of Science:

• Evolutionary anthropology
• Neuroscience
• Language genetics

Background:

• Human brain evolution focuses on globular braincase development post-Neanderthal split.
• Delayed white matter myelination in humans compared to other primates is a key developmental factor.
• Neural connectivity is genetically linked to brain/skull morphology and language readiness.

Purpose of the Study:

• To propose that interhemispheric connectivity via the Corpus Callosum is a significant evolutionary change in Homo sapiens.
• To present an evo-devo hypothesis linking Corpus Callosum myelination, brain asymmetry, and globularity to language-ready brain development.

Main Methods:

• Analysis of Corpus Callosum structure (size, myelination, fiber caliber) and connectivity patterns.
• Integration of evidence from language processing studies and brain rhythms.
• Formulation of a co-evolutionary hypothesis based on developmental and genetic factors.

Main Results:

• Corpus Callosum exhibits an anterior-to-posterior increase in size, myelination, and fiber caliber.
• Interhemispheric connectivity is more pronounced in sensory-motor areas, while higher-order areas show more intra-hemispheric connectivity.
• This pattern suggests a specific role for the Corpus Callosum in human brain organization.

Conclusions:

• The myelination of the Corpus Callosum, brain asymmetry, and braincase globularity form a co-evolutionary triangle.
• This triangle is conjectured to be a key factor in the development of the human language-ready brain.
• Evolutionary changes in connectivity, not just size, are crucial for understanding human brain specialization.