Crying is a phenomenon unique to humans. Other animals shed tears, but their tears are not linked specifically to emotions like human tears are.
Scientists now claim that we developed the ability to cry as a means to communicate our feelings before we were able to communicate with language.
Michael Trimble, professor of neurology, said biologically tears function to keep our eyes moist and fight infections.
All animals, aside from us, produce tears solely for that reason.
But the human ability to cry over intense emotions, like sadness, anger, or happiness, intrigued researchers to discover why we developed it.
"Humans cry for many reasons," Trimble said, "But crying for emotional reasons and crying in response to aesthetic experiences are unique to us. The former is most associated with loss and bereavement, and the art forms that are most associated with tears are music, literature and poetry."
"There are very few people who cry looking at paintings, sculptures, or lovely buildings. But we also have tears of joy, the associated feelings of which last a shorter time than crying in the other circumstances."
Since tears are a natural reaction to intense emotions for humans, Trimble said he hopes that people, especially men, stop feeling reluctant to express their feelings.
"We should not be afraid of our emotions, especially those related to compassion, since our ability to feel empathy and with that to cry tears, is the foundation of a morality and culture which is exclusively human."
Trimble said crying emerged in humans at a specific evolutionary turning point. He believes crying is connected with the time when our self-consciousness was developing and when we were first realizing that our fellow human beings were also self-conscious beings.
He said after we realized this, we then realized that other people can suffer, feel sadness, and disappear.
"Attachment emotionally to others, with the development of sophisticated facial gestures associated with suffering, and with loss and bereavement ensued," he said.
Trimble has written a book called "Why Humans Like To Cry."