Problems with the first life

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The amazing thing which science accepts but wishes to ignore is that life emerged the moment there was water.

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What does this mean? That life emerged one second after water appeared on the earth? After one day? After one year? Or that the oceans existed for several tens of millions of years before life emerged? All of these would count, in geology, as "the moment there was water". But tens of millions of years is a pretty long time for an ocean sized chemical laboratory to perform its experiments, yes?And, in regards to the title of the post, there was no "first life form". There was likely a very primitive replicating system, say, for one possibility, crystal defects in the surfaces of clay minerals, that no one would actually call life, and in the end, perhaps several millions of years later, something that we would definitely call a living cell; but in between there would have been a continuum of replicating chemical systems without a sharp boundary between what we would call non-living and living.The last sentence has been edited for clarity.This message has been edited by Chiroptera, 02-15-2005 17:07 AM

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By definition, there was a first single cell life form.

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No, just like there is no definite level at which water goes from "shallow" to "deep" or light from "bright" to "dim". "life" started as some replicating system, probably too simple to actually be called life, and ended as a single cell, definitely fitting what we would call "living", but there was no definite, sharp cut-off between what we would call a non-living replicator and a definite living cell.If I am wrong, then please give us the definition of "first single cell life form". Even if you can supply the definition, there would have been a precursor which, even if it could not, by your definition, be called a "single living cell", was only slightly different from this first cell.--

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The problem is that it occurred 3.8 billion years ago, coinciding (at least in geological terms) with the existence of water, a prerequsite for any life.

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It certainly coincided with the end of the period of intense bombardment of the earth by large asteroids, and this was indeed a prerequisite for life (perhaps this is what you mean), but this "instant" could easily have been a period of tens of millions of years. Plenty of time of plenty of stuff to have happened.--

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You can statistically rule out random events even over the very short span of some tens of millions of years as sufficient.

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The first replicating systems would have been very simple -- simple enough to have ocurred by random events. Once you have a replicating system, natural selection would then proceed to produce ever more efficient replicators -- a process that is very non-random.--

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Unless you want to make liars of Crick and Hoyle among many others.

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I'm not making liars of anyone. The simple fact is that there is a lot of research going on right this very instant on the question of the origin of life on earth. That Crick and Hoyle were unaware of this research or its implications is not my problem. The fact that you are relying on the non-professional opinions of persons who did no research in the relevant fields is also not my problem. I am merely pointing out the errors in your assumptions and logic as a courtesy.

Indeed, I know that Crick's work is somewhat relevant to abiogenesis. But if his argument is something on like a complex cell spontaneously appearing all at once is too improbable to contemplate, then he simply did not know the various scenarios that have been proposed. Now, if he actually evaluated the various possible scenarios and, in his professional opinion, found them flawed, that would be something to take into consideration.

For 3.3 billion years, life on Earth was confined to primitive single cell organisms, when suddenly, during an amazingly short period of 5 million years, a plethora of species with jointed limbs, internal digestive organs, eyes, mouths, etc. appeared from nowhere.This is false. First, there are many examples of multicellular life before the Cambrian -- examples of burrows, tracks, and fossils of the so-called Ediacaran Fauna.Second, molecular evidence suggests that the major phyla diverged from one another about a billion years ago -- that's rougly 400 - 500 million years before the so-called Cambrian explosian. There was over 500 million years for these different systems to evolve.

Good heavens! You need me to supply references? The Ediacaran Fauna are talked about in almost any paleontology book that speaks about preCambrian evolution, even popular science books. The molecular data indicating divergence of the major phyla over the last billion years is relatively new, but has been mention in journals like Science and I imagine should have been mentioned in the popular science press. How could you have possibly never seen this information? You could not have missed this information if you have done any real study of this. If you haven't studied this, then how the h*** can you think that you are going to be telling the rest of us what is fact and what is fiction?I suggest going to a good library, preferably the science library are at a university, and looking in the evolutionary biology section. The library should be able to help you with this.At any rate, here is what I found after a couple minutes using Google:Here is some brief information on the Ediacaran fauna. I use this site because I like the palaeos web site (they have nice cladograms, and I am a nut for cladograms).Okay, I admit the molecular chronology is a bit harder to find -- a lot of the references are journals that I can read from my computer because my university has a subscription, but you may not have access. Hopefully, you can read this article; if not, here is a portion of the abstract:

This would be an interesting topic. Unfortunately, I am not an expert in this, and I would have to do a lot of research to write something worthy of being an original post; right now, I don't have the time for it. It would be very good for me to learn something new, so maybe I'll make it a project that I'll eventually do. So maybe at some point in the future, if no one else does it in the meantime (hint, hint), the Ediacaran fauna will appear as a new topic.

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I am only familiar with Ediacaran fossils of primitive clumps and pancakes, lacking any of the distinguishing features of the species of the Cambrian explosion.

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Right now, if my understanding is correct, it is a matter of controversey whether which if any of the modern phyla are represented among the Ediacaran fauna. I think that it is the traditional consensus, still not entirely refuted, that the Ediacaran fauna represent early forms of the modern phyla; it was a new and still not entirely accepted idea that the Ediacaran fauna were a entirely different experiment in body plan.I believe that Stephen Jay Gould was a proponent of the latter idea; it fits very nicely in his beliefs there is nothing special about the species that exist today, they just happen to be the ones that exist, if one were to "run the movie over again from the beginning" life on earth could possibly be very different.It could be that the Ediacaran fauna were completely different than exists today. The idea is that the Ediacaran fauna were the dominant life forms on the planet, and the ancestors of today's fauna were a very minor part of the preCambrian ecosystems. Then a mass extinction wiped out most of the Ediacaran fauna, allowing the remaining species (our ancestors) to take over and occupy the vacant niches. One cause for the mass extinction, I believe, is that shortly before the Cambrian the earth was in a very cold state -- it is believed that the oceans may even have almost frozen completely solid, except around deep sea hydrothermal vents. This is the so-called "Snow Ball Earth" theory.At any rate, it is very, very premature to state definitely that the ancestors of modern phyla were merely single celled organisms that "suddenly" evolved at the Cambrian Explosion. Not only may the Ediacaran fauna represent early forms of some of the modern phyla, but there are tracks and burrows made by worm-like creatures, and it is accepted that all the major phyla (except, perhaps, the sponges and jellyfish) all evolved from worm-like creatures.And the molecular evidence suggests strongly that the different phyla diverged several hundred million years before the Cambrian. Of course, even though there is a divergence there is still the question:did the major body plans that define the different phyla develop over these several hundred million years?Or, was there very little differentiation, the ancestors of each of the major phyla being various species of worms that were, at that time, still virtually indistinguishable in morphology for most of this time, and the different major body plans then evolved relatively quickly, say over several tens of millions of years before the Cambrian?At any rate, I repeat, there is no evidence that the Cambrian Explosion represents a sudden event; it was "sudden" only in geologic sense, occurring over tens of millions of years which is plenty of time for major evolutionary changes to occur.And it must be stressed that the only thing the Cambrian Explosion represents is the sudden appearance of hard, easily fossilized body parts in several different phyla. Let us repeat this together; the Cambrian Explosian, in so far as it records something, does not record the sudden appearance of radically new animals, it represents the first appearance of hard, easily fossilized body parts.