Thus, decussation across the midline of the body gives an animal a survival advantage. As biologists have learned, once such an appropriate survival mechanism develops, it is maintained through ...

William Hyde Wollaston, On Semi-Decussation of the Optic Nerves. [Abstract], Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London, Vol. 2 (1815 - 1830), pp.

This is similar to the abnormal decussation pattern seen in albinos. The decussation pattern in marsupials, however, is markedly different.