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Re: Morphological evidence of marine adaptations in human kidneys

Subject: Re: Morphological evidence of marine adaptations in human kidneys
From: r norman
Date: Fri, 04 Nov 2005 10:54:21 -0500
Newsgroups: sci.anthropology.paleo
On Fri, 4 Nov 2005 12:46:59 +0100, "Marc Verhaegen"
<[email protected]> wrote:

>Med Hypotheses. 2005 Oct 29; [Epub ahead of print]
>Morphological evidence of marine adaptations in human kidneys.
>Williams MF.
>Amongst primates, kidneys normally exhibiting lobulated, multipyramidal,
>medullas is a unique attribute of the human species. Although, kidneys
>naturally multipyramidal in their medullary morphology are rare in
>terrestrial mammals, kidneys with lobulated medullas do occur in: elephants,
>bears, rhinoceroses, bison, cattle, pigs, and the okapi. However, kidneys
>characterized with multipyramidal medullas are common in aquatic mammals and
>are nearly universal in marine mammals. To avoid the deleterious effects of
>saline water dehydration, marine mammals have adaptively thickened the
>medullas of their kidneys - which enhances their ability to concentrate
>excretory salts in the urine. However, the lobulation of the kidney's
>medullary region in marine mammals appears to be an adaptation to expand the
>surface area between the medulla and the enveloping outer cortex in order to
>increase the volume of marine dietary induced hypertonic plasma that can be
>immediately processed for the excretion of excess salts and nitrogenous
>waste. A phylogenetic review of freshwater aquatic mammals suggest that
>most, if not all, nonmarine aquatic mammals inherited the medullary pyramids
>of their kidneys from ancestors who originally inhabited, or frequented,
>marine environments. So this suggest that most, if not all, aquatic mammals
>exhibiting kidneys with lobulated medullas are either marine adapted - or
>are descended from marine antecedents. Additionally, a phylogenetic review
>of nonhuman terrestrial mammals possessing kidneys with multipyramidal
>medullas suggest that bears, elephants and possibly rhinoceroses, also,
>inherited their lobulated medullas from semiaquatic marine ancestors. The
>fact that several terrestrial mammalian species of semiaquatic marine
>ancestry exhibit kidneys with multipyramidal medullas, may suggest that
>humans could have, also, inherited the lobulated medullas of their kidneys
>from coastal marine ancestors. And a specialized marine diet in ancient
>human ancestry could, also, explain the reactivation and enumeration of
>corporeal eccrine sweat glands and the copious secretion of salt tears. The
>substantial loss of genetic variation in humans relative to other hominoid
>primates, combined with the apparent isolation of early Pliocene human
>ancestors from particular retroviruses that infected all other African
>primate species, may suggest that such a semiaquatic marine phase, during
>the emergence of Homo, may have occurred on an island off the coast of
>Africa during the early Pliocene.

OK -- this one bears careful reading.  I will have to go through the
original paper to see to what degree the specialized kidney truly
reflects a marine adaptation rather than an adaptation to an arid
environment and also to what degree the presence of similar
adaptations in other terrestrial mammals  truly reflects inheritance
from marine ancestors rather than independent developments of the
characteristic in non-marine but arid habitats.  It also depends on
whether "marine" means living in an ecological niche truly closely
connected with salt water or merely living in a terrestrial habitat
not too far from the ocean.

But still it must be read and considered.

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