Reposted by Mads
Fun fact: marsupials and monotremes lack a corpus callosum. They split off from eutherians before the corpus callosum evolved.
phys.org/news/2018-09...
phys.org
Study of monotreme and marsupial brains suggests hemispheres communicated before development of corpus callosum
A team of researchers with The University of Queensland has found evidence suggesting that mammalian brain hemispheres had a means of communicating long before the development of the corpus callosum. ...