Comparative neuroanatomy of emotion expression: from flies to humans.

All animals exhibit complex behaviours that share features with those that in humans we call 'emotional expressions'. Sidestepping contentious issues about the conscious experience of emotion, their expression across species provides a wealth of detail about their emergence in evolution, the shared features that distinguish them from reflexes, and principles for their neural control. This paper provides a high-level survey of this vast field. This article is part of the theme issue 'Mechanisms, development, phylogeny and functions of emotional expressions'.