The anus may have evolved from a hole originally used to release sperm

The long-standing question of how animals came to have an anus may have been solved by studies of which genes are active during development in various animals

​The long-standing question of how animals came to have an anus may have been solved by studies of which genes are active during development in various animals The long-standing question of how animals came to have an anus may have been solved by studies of which genes are active during development in various animals