Elaine Morgan (Elaine@desco.demon.co.uk)
Wed, 26 Jul 1995 11:52:26 GMT
I hope we can take it as common ground that humans shed two kinds
of tears - one in response to an external irritant and the other not.
>From Darwin, who coined the term "psychic tears" for the second kind, to
William Frey, the only modern scientist I know of who has investigated
the subject in depth, there is general agreement on this. Reader, if
you don't understand what I'm talking about here, take a tape measure
to your ears because you must have Vulcan blood in you.
At the moment we have no consensus about how common it is for any
non-human mammal (aquatic or terrestrial) to shed tears of the Second
Kind. Contributors have assured us they have seen chimpanzees weep; in
the Valkenburg conference an eminent professor assured me without
blushing that cows regularly weep. So until some reserch is done on
this I will concede that any argument based on the heartaches of our
dumb chums is not evidence.
About the "trigeminal nonsense". The statement (that if the trigeminal
nerve is damaged people can weep psychic tears but not reflex ones) was
taken from the Encyclopedia Britannica. I have no knowledge of the
surgeon who wrote it but assume he had no ulterior motive and if he was
not properly qualified he would not have been asked to contribute. I
have not seen it affirmed anywhere else but that is not surprising.
No-one is going to inflict similar damage on another human guinea-pig
to test it. Even when such damage is inflicted accidentally it must be
pretty rare for a consultant to be curious enough to ask an eye-dabbing
patient whether his tears are of type A or type B. It was only by
accident that Darwin discovered that babies weep reflex tears before
they are capable of psychic ones; he would not have put his coatsleeve
into his son's eye on purpose.
In any case a woman I went to school with suffers from a condition
known to the layman as "dry eye". The tears which usually keep the eye
protectively coated with moisture fail to be secreted in normal
quantities and it is very uncomfortable. But tears of grief can be
extremely copious. The fact that I went to school with her does not
make this dismissable as anecdotal evidence. It is quite a common
condition and I imagine any ophthalmologist will confirm the facts.
Phil Nich says so what? It "only" means that psychic tears are not
triggered by messages along the afferent nerve which carries the
information that the eye is bothered by a foreign body or noisome gas,
and what's interesting about that? Well I find it remarkable. Ejecting
fluid from the eyes is not an obvious way to cure sorrow. What is the
point of it? It is the result of some genetic drift affecting Homo sap
and a couple of American chimpanzees and a herd of Dutch cows?
Perhaps we can agree then that it would be appropriate to look for
other vertebrates who eject water from their eyes when their eyes have
not been subjected to external irritation; and if we find any it would
be appropriate to ask when and why they do it. (Excuse, here, the
repetition from Scars - not everybody has read it.)
Marine reptiles do it - marine crocodiles, marine iguanas, marine
turtles, sea snakes. They do it in response to the same stimulus which
causes marine birds to secrete salt water from their nasal glands -
namely when they have ingested too much salt. This is not anecdotal. It
was confirmed by a whole series of rigorously controlled experiments.
When we weep or are about to or are tempted to weep we get what feels
like a lump in the throat. (Unrecontructed males who find this
discussion embarrassing are at liberty to construe this as "When women
cry they get a lump in the throat".) This is a crico-pharyngeal spasm;
the throat is trying hard to close up like a sphincter. Again, not an
obvious palliative for sorrow. Again it is appropriate to ask: what
other animal tries to close up its throat like a sphincter and when?
A seal does it when it opens its gullet to swallow a fish and a dollop
of seawater hits its stomach; the throat closes to wipe the fish dry on
the way down. Too much salt.
Now here, I admit, the argument in Scars skips hastily across a very
rickety bridge. It says: Seagulls' salt glands also secrete freely when
they get emotional e.g. over food or fighting. (True). It also says
that some marine mammals weep from emotional causes.(While I believe
this to be true, it is rated as non-proven.) So maybe at one time our
ancestors ate a lot of seafood , long enough for similar mechanisms to
evolve and to be similarly displaced onto emotional events. Yes, it
involves the unprovable assumption that psychic tears were once
hypertonic. (The salinity still varies with circumstance.)
Far fetched? Very farfetched. But (1) While it is weak on its own, its
looks better as one piece of a much larger jigsaw which all hangs
together quite neatly. (2) It asks some pertinent questions and elicits
interesting answers. It does not represent the ravings of a crackpot
tv writer. (3) It looks far-fetched compared to what? What's the best
alternative hypothesis? Zilch. The old shrug-off. We may never know,
there may be no reason.
You asked me for a prediction. In my Homo paper I rashly included a
very wild one. The psychic tears themselves are of two kinds - the
tears we shed for ourselves, and the tears we shed for others. The
second of these are later appearing in children and therefore perhaps
a more recent evolutionary acquisition. I believe the trigger for the
second kind is hormonal, like the adrenalin trigger for the
fight/flight reactions, and I think the hormone involved may be
oxytocin. There should be some non-invasive way of testing out this
idea (and proving me wrong. Wouldn't that be enjoyable?)
Next thrilling instalment: "Sweat." Watch this space.