At 01:41 PM 11/17/98 -0700, Kevin wrote:
>Greetings Brian:
>
>"Apparently you are unaware that the same word is often defined differently
in different fields."
>
>Which is irrelevant, since abiogenesis is a biological/biochemical
phenomenon, so therefore the biochemical definition is the only one that
matters.
>
My main interest is in clarity. I will concede your point to a
certain extent in that greater clarity would be achieved by
using the biochemical definition for abiogenesis and then
simply referring to the origin of life as the origin of life.
I will try to do this in the future.<<BTW, do you have some
technical references that establish this definition. If you
presented them in the past I'm afraid I missed them>>
But, if one is interested in clear communication then one should
take into account what meaning someone else might be attaching
to a word. This is not a biochem e-mail list after all.
BH:===
>"Ellington also wrote an excellent piece for t.o several years ago
entiltled: <Origins of life: A redefinition>....In particular his
statement: 'Evolution is a fact. Abiogenesis is not.' Now, if the
Miller-Urey experiment is an example of abiogenesis as used in the origin of
life community then abiogenesis is
>obviously a fact, wouldn't you agree?"
>
KO:====
>Yes, I would. But you have to understand, Ellington was writing a
simplified piece for a lay readership, not a rigorous scientific review for
his colleagues. As such, he used abiogenesis in a less rigorous fashion
(which I believe he was wrong to do). For that paper he meant it as you do:
the origin of life. In that respect I would agree that it is not a proven
fact that life arose naturally. However, ask him if abiogenesis in the
proper rigorous sense is a fact and I'm sure he would agree.
>
This seems to me an entirely reasonable explanation. Let's suppose that it
is true. If so then it indicates that Deaddog is more interested
in communicating ideas clearly than he is in using technical words.
Very commendable, IMHO.
BH:===
>"Note the word necessarily. More on this below."
>
KO:===
>You didn't answer my question, though. If "life is not metabolism based on
biomolecules, then please define
>>"life".
>
I didn't answer because I failed to see the relevance of your question.
If you insist, let me say that I prefer the definition of life I
found on a web page several years ago:
"Life is that which dies when you stomp on it"
OK, just kidding. Everyone realizes I think how difficult it is
to define life. Most other definitions I've seen attempt to
add more ingredients than metabolism. For example, I seem to
recall Eigen throwing in ability to reproduce and mutability
into the equation. These could easily become problematic of
course. I'm guessing one reason you asked this is to feel out
whether I have vitalistic tendencies. If this is the case let
me say that I believe that the physical phenomena we call life,
regardless how it ends up being defined, is fully explainable
in terms of physical laws. For the time being I'm quite happy
to take your definition.
[...]
>BH:====
>"Well, this is very interesting, but also beside the point I was trying to
make. If you look through the references below you will find examples of
experiments which qualify as abiogenesis according to your definition. Let
me turn the argument around from my previous statement. If the origin of
life occurred a la Miller, then most perhaps all of these examples would not
have anything to do with the origin of life. This is why I said that
abiogenesis (as you've defined it) does not *necessarily* have anything to
do with the origin of life on earth."
>
KO:=====
>Since abiogenesis has nothing to do with "the origin of life" as you
describe it (whatever that phrase means), your point is relevant. However,
if I may play Devil's advocate for a moment and argue from your point of
view, since life itself is complex, we should not be looking for a single,
simple origin. A number of abiogenetic mechanisms might have been working
simultaneously -- atmospheric gas reactions, hydrothermal vent reactions,
cometary/meteoric impacts, thermal copolymerization, solid-state catalysis,
etc. -- in a number of different ways to create first biomolecules, then
metabolic systems, then replicating systems and finally life. To claim that
only one mechanism could do it all is like claiming that only natural
selection or only genetic drift or only saltationist events are needed to
explain the whole of evolution.
>
Yes, very good. I like this idea a lot and would not be surprised
at all if this is the way it turns out. But my point has to do
with necessity. It isn't necessarily so. For example, there may
be many laboritory abiogenesis experiments involving conditions
never present on early earth. All of these examples of abiogenesis
would therefore have nothing to do with the origin of life.
By the way, you asked what I meant by "the origin of life",
i.e. your parenthetical comment "whatever that phrase means".
What I meant was exactly as you describe in your sentence above:
"...in a number of different ways to create first biomolecules,
then metabolic systems, then replicating systems and finally life",
i.e. the last three words.
>By the way, thanks for the references.
>
your welcome.
Brian Harper
Associate Professor
Applied Mechanics
The Ohio State University
"He who establishes his arguments
by noise and command shows that
reason is weak" -- Montaigne