A Neglected Topic

Quoted message said:

It is well known that an organism has requirements for
health. For example, if humans don't get vitamin C they
develop scurvy. There may be hundreds of requirements for
human health. We know about many of them, we have partial
information about many, and there may be many about which
we know little or nothing.

But my topic is: How did these requirements come to
be? They must all be the result of millions of years
of evolution, beginning long before our hominid
ancestors lived.

I have never come across anything written on this subject.
In fact I'm not aware of anyone (besides myself) even
talking about it. Can anyone point me to anything written
about the evolution of the requirements for health?

Would anyone like to share a thought or two on this topic?

You probably have trouble getting information on your
"topic" because it is somewhat vague and general.

There is a lot of information on specific subject, like the
evolution of vitamin C dependence (most animals can
synthesize all they need). Look at
grisda.org12096.htmOpen ↗, for example.

In general, you are asking about how organisms have become
specialized at adapting to particular environments so that
their specializations become "requirements" for survival. In
that sense, we need a particular range of nutrients and a
particular range of environmental parameters to maintain our
health. Each aspect of these requirements has been studied
at some length, but I don't know of any general work
describing all of them. Of course, the human nutritional
needs are well studied. Certainly the general subject of
adaptation is part of any general introduction to biology or
to evolution in the sense that "survival" and "fitness" are
really somewhat equivalent to what you call "health".

<[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

It is well known that an organism has requirements for
health. For example, if humans don't get vitamin C they
develop scurvy. There may be hundreds of requirements for
human health. We know about many of them, we have partial
information about many, and there may be many about which
we know little or nothing.

But my topic is: How did these requirements come to
be? They must all be the result of millions of years
of evolution, beginning long before our hominid
ancestors lived.

I have never come across anything written on this subject.
In fact I'm not aware of anyone (besides myself) even
talking about it. Can anyone point me to anything written
about the evolution of the requirements for health?

Would anyone like to share a thought or two on this topic?

I don't have links to share, but I'm pretty sure that the
thoughts that I will share are fairly orthodox.

It is useful to break the requirement for a nutrient down
into three components:
* requirement to HAVE the molecule.
* requirement to MAKE the molecule.
* requirement to GET the molecule (from the environment).

Clearly, if you need to have, then you need to either
make or get.

The general scheme for how a requirement to get arises is as
follows: The "primitive" situation is that there is a
requirement to have, which is satisfied by an ability to
make. But the molecule just happens to be available in the
environment (not too surprising for a heterotroph who eats
things that also are required to have the molecule). So, the
requirement to make is relaxed higher up the food chain.
Natural selection can lead to the loss of functionality if
the requirement for that functionality is relaxed enough.
So, the primitive requirement to make is transformed to a
new requirement to get. That requirement leads, over time,
to specific adaptations targeted at that requirement, such
as dietary preferences and specific receptors for uptake.

But that is recent evolution. More interesting to people
like me is the question as to how the "primitive"
situation arose in which there were requirements to have
and to make. There is a chicken-egg problem - which came
first, need-to-have or need-to-make? What follows is no
longer completely orthodox.

My guess is that ability-to-make arose first, though not as
an adaptation. Given the presence of the molecule, natural
selection found an adaptive use for it. Hence arises need-to-
have, and ability-to-make is transformed to need-to-make.

The alternative is that the molecule was available from the
environment because it was produced in quantity by some
process of pre-biotic chemistry. Thus, we start with an ability-to-
get, which transforms to need-to-have plus need-to-get,
which then in a few branches gets transformed into the
autotrophic need-to-have plus need-to-make.

Personally, I consider this scenario, in which hetertrophy
preceeds autotrophy, to be ridiculous. But it is very common
in the OOL community to think in this odd way.

<[email hidden]> wrote in message

Quoted message said:

It is well known that an organism has requirements for
health. But my topic is: How did these requirements
come to be?

Every organism needs a source of energy, and access to the
basic constitutents of biochemicals (carbon, oxygen,
hydrogen, and then nitrogen, phosphorous and sulphur, and
then minor constituents like potassium, calcium, zinc, and
then traces of a lot more elements).

Plants are autotrophs, and pretty much synthesise everything
for themselves. The only significant thing they can't do is
to fix atmospheric nitrogen - they have to get it from the
soil in the form of salts.

Animals have traded this independence by specialising on ready-
made food sources. They can't photosynthesise but they can
get energy by breaking down starches and sugars that they
they obtain from eating. For each metabolite, evolution has
to answer the question "do I synthesise this or do I take it
from another organism". Most animals can synthesise vitamin
C, for example, but great apes, including humans, can't. The
reason is probably because we went through a period of a
fruit diet where vitamin C was super-abundant, so losing the
pathway wasn't a disadvantage.

Now the vitamin C requirement means that we get scurvy if we
try to live entirely on preserved food.

"Malcolm" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

<[email hidden]> wrote in message

Quoted message said:

It is well known that an organism has requirements for
health. But my topic is: How did these requirements come
to be?

Every organism needs a source of energy, and access to the
basic constitutents of biochemicals (carbon, oxygen,
hydrogen, and then

nitrogen,

Quoted message said:

phosphorous and sulphur, and then minor constituents like
potassium, calcium, zinc, and then traces of a lot more
elements).

Plants are autotrophs, and pretty much synthesise
everything for

themselves.

Quoted message said:

The only significant thing they can't do is to fix
atmospheric nitrogen - they have to get it from the soil
in the form of salts.

My Vegan friends also tell me that typical plants can't make
their own vitamin B12 and, as with nitrogen, are dependent
on symbionts for this.

On a semi-related note, I wonder if anyone has argued that
these sorts of differences and dependencies are why most
animals are motile and most plants are not? Hello all you
budding genetic engineers -- if I could fix my own carbon,
I'd never leave the house!

irr <[email hidden]> wrote or quoted:

Quoted message said:

"Malcolm" <[email hidden]> wrote in
message

Quoted message said:

Quoted message said:

Plants are autotrophs, and pretty much synthesise
everything for themselves. The only significant thing
they can't do is to fix atmospheric nitrogen - they have
to get it from the soil in the form of salts.

My Vegan friends also tell me that typical plants can't
make their own vitamin B12 and, as with nitrogen, are
dependent on symbionts for this.

Plants don't normally use - or contain - B12 at all.
*Sometimes* they take up a little bit from animal waste
materials in the soil.

Occasionally they contain some analogs of B12 - perhaps
intended to disrupt the metabolisms of animal predators.

B12 is normally made by bacteria - usually in the guts
of animals.
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.

Quoted message said:

It is well known that an organism has requirements for
health. For example, if humans don't get vitamin C they
develop scurvy. There may be hundreds of requirements for
human health. We know about many of them, we have partial
information about many, and there may be many about which
we know little or nothing.

But my topic is: How did these requirements come to
be? They must all be the result of millions of years
of evolution, beginning long before our hominid
ancestors lived.

I have never come across anything written on this subject.
In fact I'm not aware of anyone (besides myself) even
talking about it. Can anyone point me to anything written
about the evolution of the requirements for health?

Would anyone like to share a thought or two on this topic?

I want to point out that nutritional requirements are not
the only requirements for health. For example, human beings
seem to require substantial exercise and some kind of
emotional satisfaction.

Mitchell Timin

--
"Many are stubborn in pursuit of the path they have chosen,
few in pursuit of the goal." - Friedrich Nietzsche

annevolve.sourceforge.netannevolve.sourceforge.netOpen ↗ is what I'm into
nowadays. Humans may write to me at this address: zenguy
at shaw dot ca

"Tim Tyler" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

irr <[email hidden]> wrote or quoted:

Quoted message said:

"Malcolm" <[email hidden]> wrote in
message

Quoted message said:

Quoted message said:

Plants are autotrophs, and pretty much synthesise
everything for

themselves.

Quoted message said:

Quoted message said:

Quoted message said:

The only significant thing they can't do is to fix
atmospheric

nitrogen -

Quoted message said:

Quoted message said:

Quoted message said:

they have to get it from the soil in the form of
salts.

My Vegan friends also tell me that typical plants can't
make their own vitamin B12 and, as with nitrogen, are
dependent on symbionts for this.

Plants don't normally use - or contain - B12 at all.
*Sometimes* they take up a little bit from animal waste
materials in the soil.

Occasionally they contain some analogs of B12 - perhaps
intended to disrupt the metabolisms of animal predators.

B12 is normally made by bacteria - usually in the guts of
animals.

Interesting... are there ideas out there on how animals got
the short end of the stick and must rely on bacteria/diet? I
suppose if you're a plant stuck in one place you either
learn how to make it or learn how to do without it.

irr <[email hidden]> wrote or quoted:

Quoted message said:

"Tim Tyler" <[email hidden]> wrote in message

Quoted message said:

irr <[email hidden]> wrote or quoted:

Quoted message said:

Quoted message said:

Plants don't normally use - or contain - B12 at all.
*Sometimes* they take up a little bit from animal waste
materials in the soil.

Occasionally they contain some analogs of B12 - perhaps
intended to disrupt the metabolisms of animal predators.

B12 is normally made by bacteria - usually in the guts
of animals.

Interesting... are there ideas out there on how animals
got the short end of the stick and must rely on
bacteria/diet? I suppose if you're a plant stuck in one
place you either learn how to make it or learn how to do
without it.

B12 is most abundant in animals. Our ancestors ate animals -
but few plants digest much animal matter directly - so that
is probably a reasonable (though slightly circular!)
explanation for why we have developed a dependency on
vitamin B12 while plants have not.

Plants also typically have symbiotic relationships of
their own - e.g. with nitrogen-fixing bacteria in their
root nodules.
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.

"irr" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"Tim Tyler" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

irr <[email hidden]> wrote or quoted:

Quoted message said:

My Vegan friends also tell me that typical plants
can't make their own vitamin B12 and, as with
nitrogen, are dependent on symbionts for this.

Plants don't normally use - or contain - B12 at all.
*Sometimes* they take up a little bit from animal waste
materials in the soil.

Occasionally they contain some analogs of B12 - perhaps
intended to disrupt the metabolisms of animal predators.

B12 is normally made by bacteria - usually in the guts
of animals.

Interesting... are there ideas out there on how animals
got the short end of the stick and must rely on
bacteria/diet? I suppose if you're a plant stuck in one
place you either learn how to make it or learn how to do
without it.

One of the main animal uses of B12 is in unsaturated fatty
acid metabolism. Normally, most of the unsaturated fats have
their double bonds at the even (or is it odd) positions, and
B12 is not needed. But sometimes a fatty acid is encountered
with a double bond in the odd position. A mutase enzyme
encorporating B12 is used to move the double bond so that
the regular enzymes can continue processing.

Plants, of course, only digest fats that they have made
themselves, or which were made by their parents. Therefore
they have no need for B12 for this purpose.

IIRC there is another use of B12 as an intermediate carrier
of methyl groups in the course of moving them from folate to
their ultimate destination, such as methionine. Plants have
apparently learned how to eliminate the middleman in this
transaction.

It may be of some evolutionary significance that neither B12
nor folate is used in the core metabolic pathways. Unless
you are a methanogen, that is. And the methanogens, whose
whole lifestyle is based on processing methyl groups, have
come up with variant versions of these two coenzymes.

Does anyone know of a good review article that surveys the
taxonomic distribution of the coenzymes and draws the
appropriate conclusions regarding when they first appeared?
Or, reviews of particular coenzymes from this standpoint? I
would be particularly interested in lipoate and biotin - are
they presumably present in the LUCA? I'm also curious about
CoA, the quinones, and the porphyrins.

It would also be interesting to look at the taxonomy of
the synthetic pathways to these coenzymes in autotrophs
and simple fermenters. Can we reconstruct the pathways
used by the LUCA?

Malcolm said:

<[email hidden]> wrote in message

Quoted message said:

It is well known that an organism has requirements for
health. But my topic is: How did these requirements
come to be?

They have to do physics, but chemistry turns out to be their
most practical method.

Beginner