Esoteric means that it is part of knowledge which is not available to most
people. It is confined, for the most part, to narrow field of study from
which it comes. It is not meant to be an insulting word. Just a statement
that a defintion of life which is confined to biochemists is restricted to a
small group of people.
It is a specific, testable
>definition that has been proven to be true over and over again in many
>different kinds of laboratory experiments.
How are definitions proven? If I take a color, and call it, say, blue..and
claim that whenever red and purple are combined, blue is the result, then
how does combining red and "purple" (my name for blue) and creating "blue"
over and over again prove my definitions?
It is misleading only to those
>who believe in a vitalistic type of life, or like you try to load life with
>requirements that in fact did not appear until after life itself appeared.
We are trying to describe reality. In reality, the genetic code exists in
even the simplest lifeforms. In fact 256 is the estimate of the minumin
number of genes needed for a fully functioning single celled organism. You
need a method of carrying information to have genes.
>In other words, a genetic code is an _a posteriori_ requirement; once we
>have life we should get a genetic code,
In order to explain how a simple cell came from simple chemicals, there must
be an explanation for how the GC and its translation machinery developed.
I will accept little steps, I don't see an immediate transformation. But I
will not accept any claim that we have proven the means by which modern
organisms on earth evolved.
I stand by my definition of life requiring a genetic code. There is no form
of modern organism which is not the result of the genetic code. A RBC,
which I concede may be alive, may have no nucleus, but it came from a stem
cell with a genetic code. It would not exist without that code.
Kevin, you said of viruses:
>. Using a definition of life that
concentrates on metabolism, however, renders viruses not alive, period.
This may make the question easily answered, but it does not explain
>fact, I believe that the best current theory about them is that they
>represent an evolutionary deadend, an organism that did not arise until
>after the appearance of the genetic code in cells, but which tried to
>produce a new type of "abiotic organism" (one that didn't need an
>metabolic system to reproduce or evolve) that ultimately failed."
In what sense have viruses failed? I contend that they are very succesful
at what they do. And where do we come off claiming they are at an
evolutionary dead end? Do not underestimate the ability of nature to come
up with interesting adaptations.
Our problem is semantics. Remember, our original disagreement is your
statement that abiogenesis has been observed in the laboratory. This stems
from your rather broad definition of life. If I also require the existance
of a genetic code, please tell me where we get false positives or negatives?
Reproduction and evolution are requirements for viability. Any organism
that has arisen must be able to reproduce to continue its form. Otherwise,
its metabolic processes simply break down and it ceases to exist.
Unfortuneately, for any lifeform for which reproduction cannot occur, it
becomes inviable in the larger sense, in that it's particular uniqueness
will completely cease to exist upon it's death. In the longer term, viable
metabolic processes must also be able to evolve, otherwise changes in the
enviroment causes them to cease.
So, while I suppose I agree with you that things which are alive are not
required to either reproduce or evolve, I maintain these are both
functionally required to explain how we got into the state we are in today.
> In fact, modern
>abiogenetic research has shown that you can get structures that are
>metabolically alive and can even reproduce themselves, but have no genetic
>code at all.
This makes the structures viable, but not necessarily life. Their
particular form will continue.
As such, if a definition for life must be based on the most
basic characteristic that is true both for all the parts of life as well as
for the whole of life itself, this definition must be based on
biomolecules/metabolic systems only and not include a genetic code.
best research so far indicates that a specific genetic code came late, long
after "life" itself had appeared.
That just moves the line of where life appeared forward a bit.
>Can the metabolic systems you speak of evolve? If so, is there a ceiling
>to their level of complexity?
They can abiotically,
Doesn't this contradict your assertion that metabolic systems are life?
but we cannot say how far this might go because on
earth (so far our only known example of life) a genetic code did eventually
arise to provide a faster means of evolution than abiotic evolution. On
another planet, where no genetic code ever arose, who can say?
It is my contention, that until a genetic code came on the scene, nothing as
complex as a simple cell, let alone multicellular life, could appear. The
genetic code does too much regulation which keeps all the metabolic
processes which are part of the cell in working condition. It substantially
You claim that I have made the logical fallacy of composition. I would like
you to explain this more fully, especially since you agree with me
(inconsistantly, I might add) that
>Being part of a living system does not make it alive.
Thank you very much,