Re: Origin - the wrong word?
- From: rem642b@xxxxxxxxx (Robert Maas, see http://tinyurl.com/uh3t)
- Date: Sun, 15 Oct 2006 17:40:45 -0400 (EDT)
From: TomHendricks...@xxxxxx
Now I'm wondering if in the phrase 'origin of life', we
should omit origin. Dictionary says, "the point or source
or cause from which a thing begins its existence."
Yet for me it is clear that life is not a beginning, its
a response to what went before.
Per various abiogenesis speculations, what went before were nothing
more than a chemical hodgepodge where high-energy sources activated
chemicals which then interacted with each other in somewhat random
ways. But then, suddenly in geological time, there was a single
successful replicator, something which consumed several of those
hodgepodge chemicals to produce more copies of itself, thereby growing
exponentially in number-of-copies, until a limit on the available
supply of one of its input chemicals began to slow the replication
rate, but already at that point billions of copies of the replicator
had already been fabricated. If we look back to the very first copy of
that particular replicator, we can mark the creation of that first copy
as the moment when life began. There's a fundamental difference between
the kinds of mixmash chemistry that went before and the single-purpose
replication that came after. That sudden change is only in a very loose
sense a response to what went before.
I find it so strange that those who say they believe in natural
selection see no response to the environment in the 'origin'. As if
that was the one and only time that there was no selection pressure
and life just popped up.
Although there is always selection pressure, without some replicator
with fecundity greater than one (hence exponentially growing in number
of copies) all that happens is that some chemical species last longer
than others before they are destroyed, but not a single chemical
species maintains its own copies to avoid extinction. So selection
pressure before replication is essentially meaningless.
We have discussed on this forum how difficult it
is to set ' a moment in time when life began.'
At the point when there were already a billion copies of one
replicator, I think we'd agree the life-began moment had already
(previously) occurred. At the point when the first ten copies of that
replicator had been generated from a single original copy, whereby
statistically it's nigh impossible for it to go extinct before it
reaches a billion copies, I'd say also the life-began moment had
already occurred. Now whether you want to set that number of ten as the
threshold, or backtrack to the very first copy of that replicator that
we know eventually got to ten and later to a billion, isn't worth
arguing over. You can make a precise definition of how far to backtrack
to set the moment when life began, and somebody else can backtrack a
different amount to get a different moment, and you have two moments
per different definitions. Nothing difficult about that.
My def. of life =
novel stabilizing responses to the environment
or
The most stable response of chemicals to that specific environment.
So you'd say the carbon dioxide atmosphere on Venus is life??
In response I'd say you're bonkers.
Oh wait, Venus wasn't the first planet to develop a stable
carbon-dioxide atmosphere, so Venus's atmosphere isn't novel?
Well then you'd say the first planet to have a carbon dioxide
atmosphere was life, and I'd still say you're bonkers.
The thing that most distinguishes life from non-life is that life
converts other materials to make more like itself, thereby generating a
*statistical* stability in lots of copies, *not* a direct stability of
simply sitting tight resisting erosion such as what zircons do.
To illustrate the difference, do a simulation of some type of
replicator, where in each time step there's a probability of making a
copy, and a probability of being destroyed, which applies independently
to each instance of the replicator in existance at the start of that
time step. Start with a hundred instances of the replicator, enough
"food" to support a thousand simultaneous instances, and let it run.
After a while the total number of instances will be one thousand, and
will remain one thousand forever after. But if you look at which
instances are originals and which are copies, over time fewer and fewer
of them will be of the hundred originals, until eventually not a single
remaining instance will be one of the originals.
.
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