Overview
- A peer-reviewed hypothesis paper by University of Minnesota neuroscientists Martin W. Wessendorf and Daniel Delie Wang proposes that the brain’s crossed layout was inherited from the visual system rather than evolving independently.
- The authors compile comparative anatomy showing every reported vertebrate has an optic chiasm and a contralateral optic tectum, which they say implies the last common vertebrate ancestor had those features.
- They trace other crossed pathways to later points in vertebrate evolution, noting that tectospinal and rubrospinal tracts likely appeared by the tetrapod ancestor while the corticospinal tract is mainly a mammalian innovation with wide species variation.
- The paper argues a crossed neocortex was the most economical solution because an uncrossed cortex would have required extra crossings or rewiring, raising transmission delays and energy costs.
- The authors stress the idea is a testable hypothesis and call for studies of fossil skulls and broader tract mapping in birds, crocodilians and other taxa plus direct tests comparing the efficiency of crossed and hypothetical uncrossed arrangements.