Why did evolution develop a digestive system that is generative of
disease?

The whole thrust of evolution is survival and procreation. Yet so many
different species produce digestive waste that creates disease for
that species and can lead to death.

Why did the evolution of the digestive system chose that path? Is that
the only way to solve the problem of deriving energy and usable matter
from food?

Secondarily, are there any organisms that produce waste that is simply
mostly depleted of usable features and not also packed in with bad
life-threatinging microorganisms?

Your question (actually there are two questions here) is a very
intriguing one; however, it would take a considerable amount of time
to research your query.

A resercher would earn only $1.50 (we're paid 75% of the fee) to
answer your question.) So, you might want to consider raising the fee.

Respectfully,
nancylynn-ga

I'm not a Google researcher and your question has alot more
implications then what I am about to pose, but I think two things need
to put forth.  First, most animals stay well clear of or cover up
their feces so contamination is not much of a problem for most
animals.  Humans and domesticated animals are put in the very
unnatural state of having higher populations in less space than would
be found in pre-agriculural times.  This both causes more biological
waste and a closer proximity to said waste since most humans and
domesticated animals stay in one area.  Also, parasites and bacteria
have a quicker rate of evolution due to the fact that many, many
generations are created over just one year.  Like any other life form,
they quickly take advantage of conditions that suit them.  So before
feces dwealing parasites could evolve, there first had to be animals
which produces feces.  Again, this is not intended be the full answer
to your question.

thnaks for the advice concerning the fee. I chose the minimum fee
because there is nothing motivating my question other than curiosity.
I am not looking for precise authoritative research results but just a
general understanding.

Perhaps I should look for an appropriate newsgroup to post my question
to. The 2nd comment has actually gone some way to increasing my
understanding.

Hello augusta-ga:

Your question won't expire for another month, so please leave it
posted here. You may well receive some more very helpful comments,
like wolfenheart-ga's.

I was just concerned that if you needed an *autoritative* answer, you
might not get it at the $2.00 fee. But you're right, you'll likely get
some very interesting feedback here!

Regards,
nancylynn-ga

I find one aspect of the question fascinating: the personification of
evolution, i.e., the idea that evolution would "choose" to take a
particular path.  At the risk of oversimplification, it seems that
there are two possibilities: either there was an intelligent creator
(e.g., God) who decided how animals would evolve, or evolution was a
random process. In the first instance, the creator decided how things
will be for reasons we may or may not ever know.  In the second
instance, things evolved the way they did because that's they way they
did; on another planet it may have turned out differently.

I'm also wondering how correct the premise of the question is.  How
many animals are killed by their own waste products? In many cases, at
least with mammals, the process gets rid of pathogens.

I found myself wondering if there's a "survival of the fittest" aspect
to this. (Can you tell I'm not a scientist :))

Out of curiosity, I started looking around. This article may be of
interest:
http://healtoronto.com/nyt290102.html

The article examines a study of chimpanzees who carry the AIDS virus,
but who don't get sick themselves. Students found the virus present in
the chimps' feces, yet the animals were healthy: 'African primates all
carry their own little viruses,' said Dr. Jonathan S. Allan, a
virologist at the Southwestern Foundation for Biomedical Research in
San Antonio. In some species, the viruses have been there for
thousands of years. And the natural host never gets sick.'"

I'm not addressing your specific question about animal waste, but
there are many reasons why we may have evolved strategies which have
bad side effects.

One example can be found by browsing through the responses to
following Google search:

[ ://www.google.com/search?as_q=sickle+cell+anemia+malaria&num=100&hl=en&ie=UTF-8&oe=UTF-8&btnG=Google+Search&as_epq=&as_oq=&as_eq=&lr=&as_ft=i&as_filetype=&as_qdr=all&as_occt=any&as_dt=i&as_sitesearch=&safe=images
]
Google Search: sickle cell anemia malaria

Sickle cell anemia is a genetic disease passed from parent to child
through a recessive gene. Because of this, the child must inherit the
sickle cell anemia gene from both parents in order for the child to
receive the disease. If a child only receives the gene from one
parent, the disease is not present in the child.

It has been noted that the gene is very common among people who live
in areas with malarial mosquitoes. So, the question arises: What
possible benefit exists that has allowed this gene to become so
widespread? The answer is that even though sickle cell anemia is not
present in people with only one copy of the gene, the very presence of
that recessive gene in their body makes them partially immune to
malaria! Thus, people who are carriers of the sickle cell anemia gene,
but do not actually have the disease, have a greater chance of
survival than people who do not carry the gene!

I hope this provides you with some food for thought,

/ephraim

I think that your question stems from common misconceptions about
evolution.  I suggest that you read a transcribed lecture by Francois
Jacob (1977) called "Engineering and Tinkering" [if memory serves]. 
We should avoid the tendency to assume that organisms are the way they
are because they are perfectly adapted to whatever modern environment
that they live in.  Organisms are combinations of chance (what novelty
did evolution have to work with? - if photoreceptive pigments never
appeared by chance, how could evolution even make an eye?) and history
(we are mostly what are ancestors were... which may or may not mean
that we are well suited to our environment).  Lastly we must consider
that organisms and their features must only be "good enough," not
optimally adapted.

An example might be whales.  Surely gas exchange at the ocean surface
using mammalian lung tissue is not the best way to accomplish this
task for an aquatic animal.  However, because whales have a
terrestrial mammalian ancestor they are stuck with this method of gas
exchange (at the present).  Clearly this is not an optimal adaptation
- but it is evidently good enough to permit survival.

I hope this will help you rethink you feces problem :-)

I'm sorry - the article is "Evolution and Tinkering"

"The whole thrust of evolution is survival and procreation." I find
this statement problematic, because it has not been proven. It is only
a theory, and there have been discoveries of random mutations which
seem to have no purpose than to ruin species. I believe for something
to have a "thrust", there should be intelligent control. Since
evolution is thought to work without anybody controlling it, it just
develops species with no thrust.

Macroevolution is a theory that most people accept but as it was
stated here, macroevolution creates mutations and mutations take AWAY
from the organism, mutation does not ADD new information TO the
organism. Thus mutations WEAKEN the organism and do not make it a
better or stronger organism.

"Organisms are combinations of chance (what novelty
did evolution have to work with? - if photoreceptive pigments never
appeared by chance, how could evolution even make an eye?"

I personally don't believe something can come from nothing. Evolution
assumes that there was never a real "beginning" composed of absolute
nothingness -- it assumes that some building blocks were always
present and suddenly began to form into things. Where then did the
blocks come from? Evolution does not answer this question because it
can not. It is against the law of Entropy to state that something can
come from nothing because everything is in a state of decline once
left alone. The universe left alone could not become a bigger, better
universe (by our standards) without violating this law.

Here's some interesting information to tool around with:
Science Against [Macro] Evolution
http://www.ridgenet.net/~do_while/sage/newsletters.htm

Hi 

I think that instead of looking at it as organisms developing a
digestive system that is "generative of disease" that it might be
better to look at it as organisms have developed a digestive system
that deals with a dirty situation and is mostly successful at
preventing disease.

The digestive system has a purpose - to absorb nutrients - and to
acheive this purpose, it must have a thin layer of relatively exposed
tissue available to absorb the nutrients.  In a small organism this is
not a problem and the whole surface of the organism can be used to
acheive this goal (like bacteria).  In larger organisms, it's just not
practical to leave your thin absorbtive surface exposed to the
environment and you need to eat such quantities of material that are
difficult to come by by simply absorbing them from the environment. 
The solution here comes in two parts - you either spread your
absorbtive surface over a large spread of relatively protected space,
like plants and trees do with roots- or, you develop a "gut" into
which you can pack nutritive containing, more unfortunate organisms
for digestion at your convenience.  Digestion at your convenience
means, however, that you will contain within your gut a considerable
amount of nutritive material that many organisms will also wish to
consume - and some of these organisms (such as bacteria) will be
ingested with the foodstuffs themselves.  Therefore, you must deal
with organisms living in the food that you wish to digest.  As this
problem has been occuring for ages - organisms have adapted to the
situation such that some of the bacteria living in your gut has
entered into a symbiotic relationship with you - bacteria can digest
some food products that we cannot - in doing so they provide food and
vitamins that we would otherwise not have available.  In turn, we
provide a nice, warm, food-stocked environment in which they can
dwell.

This situation presents a problem when the bugs living in your gut
decide that the food within the gut is not sufficient, and that your
innards, with only your thin digestive tract layer separating the
twain would make for far better eating.  Now, your body defends
against this - and your gut contains a large number of immune cells
whose sole purpose is to repel attacks across your gut.  Sometimes
this is not sufficient, and the organisms are able to gain access to
your body, and disease ensues.  This is made much more rapid if holes
are introduced into your digestive tract by knives, guns, or other
sharp pokey things (sometimes blunt objects can also disrupt the
digestive tract as it tends to be full of gas that makes it pop like a
balloon when squeezed too hard).  On the whole, however, your gut does
a remarkable job of getting the nutrients into your body, while
keeping all of the other bad stuff out.

synarchy

Just a quick thought without proper research but nature has it's own
way of thinning out the population.  Survival of the Fittest.  This
would have the strongest of the species any species mating and
creating a stronger species.