Re: tears

David Froehlich (
Thu, 19 Oct 1995 22:09:28 -0500

On 18 Oct 1995, H. M. Hubey wrote:

> >Tears proportionally contain the same amount of saline as the rest of the
> >body. When a tear is excreted, the body has lost that much mass, a small
> If you lose fluids you have to drink water. That means you can lose
> salt via tears and drink water and excrete salt.
> I wonder what it is about people like you who can't understand
> what you read.

Have you ever heard of kidneys? These seem to be much better at getting
rid of excess salt. Isotonic tears are not an efficient method of
loosing salt, urine is. Besides which, if you are living in a marine
habitat where is this fresh water coming from?

> >salt proportion of the body a "salt-excretion mechanism" if you wish. It
> >doesn't change the fact that tears are not an effective mechanism for
> >ridding the body of excess salt.
> Anything that gets rid of salt can be a salt excretion mechanism.
> I agree that unless they wept a lot it would be ineffective,
> certainly not as effective as kidneys or sweating but so what.

So what? Producing isotonic tears as a salt excretion mechanism only
works if you have voluminous amounts of fresh water. The energetics of
the situation (you would have to expend a lot more energy to expel salt
in this manner than with concentrated mechanisms such as using the
kidneys) would seem to indicate that the use of isotonic tears is
extremely unlikely.

Another point, I just looked up the comparative anatomy of the kidney in
primates. The loop of henley (the actual structure involved with the
recapture of metabolic water from the urine) is virtually identical in
all hominoids. Given an AAS period in hypertonic sea water, there should
be some adaptation to greater recapture since osmosis is going to dry the
organism out (ie an increase in the length of the loop of henley).
Interestingly, there is no evidence of this change. I wonder what AAS
proponents make of this anotomical structure? To my eyes it seems to
falsify the AAS position (at least for AAS in seawater). Any comments?

David J. Froehlich Phone: 512-471-6088
Vertebrate Paleontology Laboratory Fax: 512-471-5973
J.J. Pickle Research Campus
The University of Texas, Austin, Texas 78712