Re: Morgab tears /salt
Alex Duncan (aduncan@mail.utexas.edu)
15 Nov 1995 02:23:21 GMT
In article <22834558wnr@desco.demon.co.uk> Elaine Morgan,
Elaine@desco.demon.co.uk writes:
>If the danger was bacterial or viral, there would be no immediate
>physical irritation to the eyeball of the kind necessary to trigger
>off reflex weeping.
>
>Mammalian tears contain a variety of protective elements. One of the
>most effective is lysozyme; some of this is found in the tears of the
>higher primates. (A. Fleming, Proc. Roy. Soc. (London) B93, 306 (1922))
>It has been shown to inactivate the viruses of many infections such
>as herpes simplex (if you get a cold sore on your lip get a friend to
>weep onto it) and herpes zoster and warts and vaccinia, etc. (R.
>Ferrari et al, Nature, 183, 548 , 1959)
>
>Prediction time. This new hypothesis would predict that among the
>differences between chimps and humans would be a higher concentration
>of protective substances in the tears of humans, especially in the
>latest-evolved type, namely psychic tears. Okay?
There's one particular point here that is unclear to me: are you
suggesting that there are lots of viruses and bacteria present in sea
water that are capable of infecting humans? If so, I would like to see
some documentation, and frankly, documentation based on samples from
modern sea water wouldn't do, because modern sea water is so contaminated.
>"In human tear fluid, relatively high concentrations of proteins like
>immunoglobin A, lactoferrin, tear-specific pre-albumin, and lysozyme
>are found, besides high activity of the tear-specific enzymes
>peroxidase and amylase." ("Species differences in tears; comparative
>investigation in the chimpanzee" by VMW Bodelier et al. Primates,34(1)
>pp77-84, Jan 1993)
>
>"The species comparisons performed until now indicate that human tears
>remain unique in this high content of lactoferrin" (Ibid)
>
>And, as previously noted, psychic tears contain more of
>these proteins than the old-fashioned reflex ones.
Let's think this though in the simplest possible manner. We have a
potential difference between humans and chimps (protective elements in
tear fluid) that needs explanation. The possibility that human tears may
have higher concentrations of these "protective" materials suggests that
humans are more susceptible to infection via the eye balls than chimps.
Well, what do humans do differently than chimps that might make us more
susceptible to this kind of thing? The most obvious one that jumps to
mind is that the majority of humans live in incredibly dense population
clusters in comparison to all other primates. Urban living has been
demonstrated time and again to put humans at special risk for the
epidemic spread of contagious diseases. Urbanity has been a feature of
human social behavior for at least several thousand years, and it could
be argued that conditions for epidemic spread of diseases have been
present at least since Neandertal times (cave dwelling). Thus, the
simplest explanation for differences between the content of tears in
humans and chimps is that there has been selection in humans for
individuals who are capable of withstanding the viral/bacterial onslaught
that occurs in dense population clusters.
This explanation has two major advantages over the one Ms. Morgan has
offered:
1) It is based on observed differences in the lifestyles of chimps and
humans.
2) It doesn't require an implausible "aquatic phase" for which no good
evidence has been found.
Alex Duncan
Dept. of Anthropology
University of Texas at Austin
Austin, TX 78712-1086
512-471-4206
aduncan@mail.utexas.edu
|