Re: Morphological evidence of marine adaptations in human kidneys

r norman:
> Sorry, you are quite wrong, here.
>
> Vertebrate kidneys, prior to the mammalian "invention" of the Loop of
> Henle, do not have the ability to produce urine more concentrated than
> the body fluids. Hence, animals that either live in a marine
> environment or a very arid terrestrial environment (in both cases, no
> access to fresh water) have a difficult time eliminating salt but
> retaining water. Since their kidneys are not capable of doing that,
> they developed extrarenal salt excreting glands. Chondricthyes, like
> sharks, have rectal glands. Bony fish use their gills and gut to
> eliminate salts. Amphibians never figured it out and, with one
> exception (Rana cancrivora in SE Asia) can't live in a marine habitat.
> Reptiles (including birds as a variety of reptile) have a variety of
> glands -- in their nose, in their mouth, and in the orbit of the eye.
> The reason for those locations is that there were already secretory
> glands there -- like tear glands and salivary glands -- that could be
> modified for the new function of salt excretion. The salt gland does
> NOT "protect" the eye. It maintains the body's salt and fluid balance
> (osmoregulation). The other glands, whether nasal or sublingual or
> rectal, also do NOT protect the nose or tongue or rectum.
>
> Mammals are completely different. The Loop of Henle and the medullary
> system allows the mammalian kidney to produce a concentrated urine.
> So mammals simply don't have extra-renal salt excreting glands. Our
> tear glands do NOT derived from salt glands!

Unfortunatelly, I only have few minutes before my time to sleep. I
wanted to write something other day, but there is definitely something I
must write now. BTW, thanks for all the nice info.
First, "The reason for those locations is that there were already
secretory glands there -- like tear glands and salivary glands -- that could
be modified for the new function of salt excretion." How come those glands
have the ability of modification? My guess is because of what I said (at
least for tear glands). But, of course, I didn't have time to check if this
is really sure.
Ok, now mammals. It is noticed that mammals's tear glands don't
modify for salt extraction, because of the function of kidneys.
Now, in humans, tear production is associated with babies. And
crying, as well. As I could figure out, kidneys don't function quite well in
babies (unfortunatelly, I didn't have time to check what is the real truth).
In my scenario, sea is a safe place for humans. Safe place, hence
good for babies. The problem with sea, though, is salt extraction. The other
problem is waves. You can lose your baby amongst waves, very easily. When
man falls from a ship into sea, the first thing is to keep sight of him. If
you lose sight, you could never find him again. And this is from a hight of
a boat. And what if you are amongst waves yourself. You could lose person
which is 10 yards from you. The best thing in this situation is to yell.
Produce sound. Our babies are producing tears, and sounds. And, look at
that, this is exactly what is needed in this situation. There are some
unsolved questions in this scenario, but this scenario fits very well into
what we have. Explains yet unexplained. I hope you will ask more questions
which I (or whoever is goodwilling) would need to solve. -- Mario


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Relevant Pages

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  • Re: Morphological evidence of marine adaptations in human kidneys
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