Re: There's something fishy about human brain evolution

"Lee Olsen" <paleocity@xxxxxxxxxxx> wrote in message
news:1140543050.180323.140160@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

r norman wrote:
stephen.cunnane@xxxxxxxxxxxxxx
819-821-1170
Natural Sciences and Engineering Research Council

There's something fishy about human brain evolution

But, he says, the evidence of the importance of key shoreline nutrients to
brain development is still with us - painfully so. Iodine deficiency is the
world's leading nutrient deficiency. It affects more than a 1.5 billion
people, mostly in inland areas, and causes sub-optimal brain function.
Iodine is legally required to be added to salt in more than 100 countries.

Could you tell me if iodine (then to thyroxine) is required by
elephants and chimps for their brain development also?

Is iodine is required more for brains than
for other organs or generally? Iodine-
deficiency in humans can certainly have a
devastating effect on the brain, but AFAIK
those problems arise in the early stages of
development, while in the womb. Iodine
deficiency later in life seems to lead merely
to goitre, as it does in other mammals.
All animals require trace levels of iodine,
and will react adversely to deficiencies.

If it is, then
would an elephant, for instance, require more milligrams of iodine per
month for normal growth than a chimp or early Homo simply because it is
larger? See what I'm getting at?

The 'iodine-cycle' is well worth a
thorough investigation. I doubt if it has
had one. The problem is that iodine is
highly water-soluble, and leaches out,
even from inland salt-deposits. There
must be a slow infiltration back from the
sea, as migratory species eat marine
resources, and are then consumed by
inland species which, in turn, are
consumed by others. This would cover
birds and insects. Locusts, for example,
must move fair amounts of iodine around.
Likewise, blood-sucking species and
parasites (mosquitoes, tics, vampire
bats, etc.) must also move it around.
The total quantity of iodine transported
inland every year is obviously not large,
but must be enough to maintain the
necessary levels.

Elephants don't eat fish and frogs.

How do you know? They like watery
locations and vegetation. Mosquito
larvae might be rich in iodine.
Elephants would consume those and
other insect larvae with their vegetation

If the savanna (or savanna-like) in any way contributed to iodine
deficiency, then this should show up even more in elephants one
would think.

Not really. Elephants are highly mobile,
and migratory. The problem would be
more acute among strictly territorial
inland vegetarian species -- particularly
those located in isolated eco-systems
far from the sea, especially mountains.

The volume of iodine must have been available elsewhere out on
the savanna. Cunnane is making it sound like the only place to get
iodine is by children catching frogs.

Most forms of carnivory (including
that on bugs and termites) should
recruit some iodine.

However, the crucial point where all
this is relevant to human evolution
is in sweating. Kidneys can prevent
loss of iodine (and other salts) in urine,
but there is no equivalent mechanism
in sweating -- which must (pretty well)
exude the salts it finds circulating in
the blood. Sweating could not have
evolved in any species restricted to
an inland diet. It certainly did not
evolve on the savanna.


Paul.




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