Post by Bob T. Post by firstname.lastname@example.org
The record shows a rush of initial life forms during a narrow sliver
of earth's history. If that is so, why did it happen?
You are presumably speaking of the Cambrian Explosion, which was early
in the history of multi-cellular life forms. The general explanation
is that certain forms of life had passed a threshold that enabled them
to become much larger and more complex than any living thing before.
When that happened, a vast number of ecological niches opened up that
had never been exploited before.
It's hard to tell what he's talking about here. The Cambrian Explosion refers
to the massive radiation of animals and increase in diversity of life on Earth
which began about 500-600 million years ago. The reasons for this are no fully
understood, there are several hypotheses, I think the leading one is that it's
connected to a large increase in atmospheric oxygen. There was, actually no
oxygen free in the atmosphere at all until photosynthetic organisms arrived in
the ocean first filling the ocean with oxygen to the point of saturation and
then it spilled out into the atmosphere. This allowed for respiration and a
whole new slew of life forms.
However, this is not a rush of 'initial life forms' early in Earth's history.
Life on earth goes back something like 4 billion years. I dunno wtf he's
talking about, there also was a major radiation of mammals about 65 million
years ago following the demise of the dinosaurs. This is a case of mammals
filling all the niches that reptiles were no longer there to fill. These sorts
of major extinction / radiation events are relatively common, in fact we are
smack in the middle of a major extinction event right now (caused entirely by
humans) and I'm sure an interesting radiation event will occur once we're done
Post by Bob T. Post by email@example.com
Why hasn't it happened over and over again?
It does, see what I wrote above, or what Bob wrote below.
Post by Bob T.
Because the ecological niches are already filled more competitively
with existing species.
For what JEH says is apparently the 'central question' of this thread:
how did the initial cooperating cells of
any or all of the life systems on our planet, manage to initiate life
by accident or happenstance, and having done so only during a narrow
period of our earth's existence and nowhere on any other planet in the"
sky?It's kind of hard to explain to you how life might have arisen spontaneously
on Earth without getting very technical. Phosphlipid bilayers, which form the
membranes for cells, can form spontaneously in water due to their physical
construction - they are formed of molecules which are partially water-phobic and
the other half is attracted to water. Therefore they tend to line up in a ring
in water, on their own. Look up 'Protobionts' if you're bored to learn how
these things can spontaneously form (this has been done in a lab). Then you
need some basic organic materials, carbon based chemistry, amino acids to be
produced. Again, this has been done in labs, but we're not exactly sure what
the atmosphere was like back there, and this is all theory at this point. But
it's not happenstance, or chance, or luck, or anything like that.
Water is a requirement for life as we know it, and that obviously limits the
planets where this can occur. In fact we know of no other planet that has the
necessary conditions to raise life as we know it. As far as why this doesn't
continue happening? Nowadays if any tiny organic molecule is spontaneously
formed, it will be nearly immediately consumed by some form of life already on
this planet. There won't be time for hundreds of millions of years to pass for
the one protobiont in the ocea to eventually develop into complex life.
And why was it that there is a specific time-frame in the earth's
history, when the bulk of earth's lifeform initiations occurred...Why
not in later periods? And who or what selected that sliver of earth's
time? You seem so certain you know it all...I would like to hear your
answer."What are you talking about, exactly? If you get more specific you can
get an answer, what sliver? Life on earth appeared nearly immediately after big
pieces of the solar system finally stopped crashing into the nubile earth.
Earth is about 4.5 billion years old, life on earth about 4. It took a great
deal of time for life to radiate outword. It took photosynthetic organisms to
populate the atmosphere with oxygen, it took plant life to move from the oceans,
etc. It's a long, long story.
Also as an aside, I think it's pretty silly that a God would have ever had to
'intervene'. Certainly, we can see no evidence for any divine intervention in
the universe anywhere, and everything seems to follow along predefined laws.
Did God write the laws? I dunno, but if he's all knowing, I'm sure he would
have had little more to do that to set the initial condition, and already know
how it would turn out. But if he does exist, and he gave us all rational and
inquisitive minds, should we just ignore what they tell us? I don't really care
if there is a God, I just want the science of evolution to be better understood,
because this really IS how complex life arrived on this planet, and damnit it's
interesting! It's even more miraculous, to me, than the notion of a diety going
'POOF' and making everything with magic.
I see the position (chance fusings of molecular debris that initiate
life) as every bit an act of belief as would make any religionist
proud, being totally absent sound scientific proof, and not being
repeatable in a lab."
I'm sorry but this is just ignorant, there is sound scientific proof, and these
things have, in fact, been done in a lab.
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