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This paper challenges the classical dual‐factor model of neocortical development by providing compelling evidence that mechanical morphogenesis plays a fundamental role in shaping cortical folding, thickness, and connectivity across 70 primate species. The authors integrate high‐resolution MRI data, phylogenetic comparative methods, and advanced surface morphing techniques to demonstrate that brain volume is a strong predictor of neuroanatomical similarity and behavior, independent of genetic relatedness Paper on Primate Neocortical Organization

Comprehensive Review of Neocortical Organisation in Primates

This paper redefines our understanding of neocortical development by proposing that, in addition to the widely accepted genetic and experience-dependent factors, mechanical morphogenesis is a critical determinant in a 3-factor framework governing cortical folding, thickness, and connectivity. The work is based on an extensive analysis of high-resolution MRI data from 70 primate species across diverse phylogenetic backgrounds. By comparing cortical features such as folding patterns, cortical thickness, and whole-brain connectomes, the authors have demonstrated a striking correlation between brain volume and neuroanatomical organization Primary Study Findings.

Key Findings and Methodological Strengths

• Integration of Mechanical Morphogenesis: The paper provides evidence that the mechanical instabilities that occur with brain growth lead to a convergence in cortical folding, even among phylogenetically distant species Mechanical Morphogenesis Evidence.
• Robust Phylogenetic and Anatomical Analysis: Leveraging both surface morphing techniques and phylogenetic comparative models, the study demonstrates that neuroanatomical similarity (folding, thickness, connectivity) correlates more strongly with behavioral similarity than with phylogenetic proximity. This suggests that mechanical constraints could be driving a form of convergent evolution, particularly in species with larger brain volumes Behavioral and Anatomical Correlations.
• Methodological Rigor: Detailed methods employing custom software tools (Reorient, Thresholdmann, BrainBox, MRtrix, and mvMORPH) and advanced MRI segmentation techniques ensure a high degree of reproducibility and data accuracy, although some limitations inherent to MRI resolution and model assumptions remain Methodological Details.

Critical Analysis and Limitations

While the paper is innovative in integrating mechanics into the framework of neocortical development, several limitations should be noted:

• Dependence on MRI Data: The study’s reconstructions, despite being high resolution, may not capture the full complexity of microstructural features, potentially impacting the granularity of folding and connectivity metrics MRI Data Limitations.
• Assumptions in Phylogenetic Models: The reliance on the Brownian Motion model for ancestral state reconstruction simplifies evolutionary processes, which may not capture complex adaptive landscapes, although the authors have acknowledged these constraints Phylogenetic Model Limitations.

Conclusions and Broader Implications

The study significantly advances our understanding by proposing that mechanical morphogenesis is an essential third factor shaping neocortical organization. This integrative approach not only provides a parsimonious explanation for the convergent evolution of brain features across diverse primate lineages, but also suggests a new paradigm for predicting behavioral similarity based on neuroanatomical characteristics rather than solely on genetic proximity Integrated Conclusion.

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