Tears - A Unique Mystery about Humans

Humans are the only species who shed tears as a result of emotions. Other species also shed tears, but only due to pain or irritation. Women are generally considered more emotional, so tears are often regarded as a weapon for them. Charles Darwin once told that emotional tears are purposeless. Still 150 years after Darwin, the human tears are a mystery for scientists. Tears are often considered as water by some people and often regarded as a sign of weakness, but this myth will be broken in this article.

What are tears made of ?

Tears are not just water, as often considered by some people. If it is just water then it may evaporate easily due to body heat or environmental heat, which would make it harder for eyes to remain wet. It is a mixture water, fat and protein. Basically it contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, immunoglobulins, glucose, urea, sodium, and potassium. The proportion may differ for different people depending on time and emotion. Normally tears are secreted in small amount to clean the eye and keep the cornea wet. They shed away on cheeks only when they are secreted in excess amount and nasal passage can't handle that flow.

Why Tears are necessary for our body ?

  • Tears keep eyeball wet, which is necessary to see properly.
  • Tears pass through to our nostrils through a nasal passage to keep the nose wet and trap the dust and microorganisms in the breathe.
  • Tears contain lysozyme, which can kill 90 to 95 percent of all bacteria.
  • Crying makes our body to release feel-good endorphins, which are also released when we do some physical workout or when we laugh.

Tears are of three types
  • Basal Tears: They are always there in the eyes to nourish them and keep the eyeball wet.
  • Reflex Tears: They protect our eye from irritants such as dust in wind, onion and smoke.
  • Emotional Tears: These tears come out as a result of some emotion such as joy or sorrow.

All three types of tears have different chemical composition.

Tears and the emotional connection

Some psychologists believe that tears are there because man is a social animal. It tells the people near us that we are temporarily going through some problem that is beyond our ability to cope. Emotional tears are different from those tears that comes out due to onion chopping. Emotional tears are more viscous due to more protein content and they stick to the skin and remain on the cheeks for a longer duration, so that someone close can notice them easily. Same neural areas of brain are activated, when we cry or when we see someone crying. Your tears can neutralize the anger of the person in front of you. Being able to cry and the ability to recognize it and respond to it, is an important characteristic that humans got in the process of evolution. Tears can sometimes save a person from further argument and punishment, which makes it a protective mechanism for our body.

History of Research on Tears

  • Around 1500 BC people use to think that tears originate from heart.
  • During Hippocrates' time (460 BC-370 BC) it was thought that mind triggers the tears.
  • In early 17th century it was believed that emotions heat the heart, water vapors are formed there to cool it down, then those vapors rise upwards and condense near eyes and come out as tears.
  • Lacrimal Glands were discovered in 1662 by a Danish scientist named Niels Stensen. These glands also referred as tear glands were found responsible for generation of tears. Stensen also told that tears are there to keep the eyes moist.
  • Vingerhoets, a clinical psychologist, published a theory in 1960. According to that theory humans evolved from aquatic apes and tears helped us live in salt water. This theory was totally rejected by scientific community.
  • Biochemist William Frey popularized a theory in 1985 that crying is a mechanism to remove toxic substances from the blood which build up due to stress.

Today some of the above theories seems to be foolish, but during those times that was a scientific belief. Today we know a lot more than that only because of those theories. But still tears are a mystery.

Some Facts about Tears

  • A newly born baby can't produce tears even if they cry till the age of six weeks.
  • Quantity of tears decrease as we age.
  • Biochemically tears are similar to saliva.
  • According to some researches women cry more than man. Approximately five times more.
  • The crying session is also lengthier for women. Average crying session of women lasts for six minutes, while it is two to four minutes for men.
  • Happy tears and sad tears are chemically same.
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