Posted on Saturday, September 09, 2006 - 7:51 pm:

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Tears come from two places. First, from tiny glands (called the lachrymal glands), about the size and shape of a shelled almond, located just above the outer corner of each eye. Also, cells in eye membranes make tears — the ones that line the eyelids and cover the exposed part of the eyeball.

These glands and cells constantly form tears. The tears ooze through tiny ducts from the lachrymal glands into the eyelid membrane and thence over eyeball membranes where they flush the eye. That happens all the time, automatically, to prevent eyes from drying, which can harm vision and even lead to infection.

Events (like a fleck of dust landing on the cornea, bright lights shining into the eye, or eating chili peppers) can trigger a tear reflex response. Strong emotions — both laughter and sorrow — can also cause tears to flow.

The brain triggers emotional releases, such as laughing and crying. Perhaps the source of such feelings is indeed the soul or spirit but that’s beyond the realm of science.

Many animals seem to experience sadness as we do. They cry and whimper but few if any spill tears while crying. (A zookeeper, though, once told Charles Darwin that sometimes elephants weep from sorrow.)

Animals do shed tears, however. A crocodile’s third eyelid flushes tears across the eyeball to lubricate its passage and to clean and protect the eye. Birds moisten their eyeballs with tears while flying. An aardvark’s tear membrane protects its eyes against termite bites. Polar bears, horses, and dogs produce tears too.

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This is the second of a two-part answer. This part considers whether other primates and animals weep also. The first part discussed why people weep. See Further Surfing below.

Right: [Corel] A gorilla emotes.

Darwin noted that some human emotional expressions may have started as part of a physiological function: for example, baring the teeth to bite food. The function, however, took on meaning and became a form of communication: baring the teeth signals anger.

The same may be true for the animals, from which we sprang. Marmoset infant monkeys cry for attention. They also cry when older to signal to an adult that they want to be carried.

"Chimpanzees do make upset vocalizations when they are being weaned by their mothers or have lost their mother or other individual," says Anne Pusey, ecology, evolution and behavior professor at the University of Minnesota. She also directs the Jane Goodal Institute's Center for Primate Studies. "They whimper and cry and scream. When we hear these calls, the emotion involved seems obvious. However, they do not weep in the sense of producing tears. I have seen an adolescent male whimpering when he lost sight of his older brother with whom he had been traveling."



Infants of many mammalian species, including rats, cry. Moreover, when a baby rat cries, often his mother brings the fallen pup back into the nest. This is probably a straight-forward communication as it is with humans. However, psychologists at the University of Iowa aren't convinced.

The Iowan researchers can induce the same crying sounds by producing large decreases and then increases in blood flow. The blood flow also lowers when baby rats get cold. Thus, they conclude rat babies cry in the same way that we sneeze. Of course, the rat baby could also be crying because he's cold and wants his mother to know.

All young mammals make cries when separated from their mother, says Jaak Panksepp, a psychologist at Bowling Green State University. If you're willing to call this crying, then "certainly other animals show this emotional response," he says. "Some of us take seriously that animals do have emotions."

Charles Darwin said that the keeper of the Indian elephants at the London Zoo told him the elephants would sometimes weep from sorrow.

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