All mammals produce tears from glands in the eye to lubricate the cornea and flush out dust and dirt. But crying as a response to emotional distress might be uniquely human. Elephants are known to shed tears, but we don’t know their state of mind and it may be that we only call it ‘crying’ because they already have such sad-looking faces.
Behavioural neurologist Michael Trimble suggests in his book Why Humans Like To Cry that crying evolved along with the higher mental faculties that allow us to recognise the tragedy of life – as opposed to the basic animal emotions of fear, hunger or pain. Crying, he suggests, provides an almost pleasurable form of release.