Tears, what are they good for? They certainly embarrass us when they suddenly start gushing out of your eyes at the theater when the leading character finally finds long lost love or when your significant other unexpectedly decides to break up with you over dinner at a busy restaurant. However, a leading scientist says that the human phenomenon of emotional crying is hugely important and developed as a way for humans to communicate how they feel before the emergence of language.

Leading expert in neurology Michael Trimble, British professor at the Institute of Neurology in London, says that there must have been a time in human evolution when tears represented something greater than their simple function of lubricating the eye.

In his new book, Why Humans Like To Cry, Trimble tries to explain the mystery of why humans are the only species in the animal kingdom to shed tears in response to an emotional state. In his book, Trimble examines the physiology and the evolutionary past of emotional crying.

Trimble explains that biologically, tears are important to protect the eye.  They keep the eyeball moist, flush out irritants and contain certain proteins and substances that keep the eye healthy and fight infections. He explains that in every other animal on planet Earth, tears seem to only serve these biological purposes.

 However, in humans, crying or sobbing, bawling or weeping seems to serve another purpose: communicating emotion. Humans cry for many reasons- out of joy, grief, anger, relief and a variety of other emotions. However, our tears are most frequently shed out of sadness. Trimble said that it was this specific communicative nature of human crying that piqued his interest.

"Humans cry for many reasons," he told Scientific American. "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," he said. "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."

Trimble says that he hopes his research will help many people, especially men, cast away their shame when they are seen turning on the waterworks in public. He said that tears are a natural human response to personal suffering and feeling compassion for others.

"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," he added.

Looking at tears from a neuroscience point of view, Trimble suggests that emotional crying must have developed in humans at a specific evolutionary point. In his book he suggests that the emergence of emotional crying must have been connected with the "dawning of self-consciousness" and the "development of theory of mind" when our ancestors realized that their peers also possessed self-consciousness.

He explains that this is what led the realization that the self and others can feel distress, suffer anguish and disappear.

"Attachment emotionally to others, with the development of sophisticated facial gestures associated with suffering, and with loss and bereavement ensued," Trimble said, according to Scientific American.

"All this before the development of our elegant propositional language. The emotional responses became largely unconscious and innate, and identification of tears as a signal for such distress was an important addition the so called Social brain, the circuitry of which can now be identified in the human brain," he said.