“We have a pretty good idea what happened”. Really? Can you give some cites for that, I would like to read up on this.
Frankly, I find it a long stretch to go from stringing together a few random molecules in a test tube to making a fully functional DNA molecule which contains the kind of data required for the maintenance and replication of life.
But putting that aside, would it be a practical proposition to have a RNA/DNA molecule floating around without the benefit of a protecting and nurturing cell structure?
Seems to me that the first rays of sunlight to strike it would destroy it.
It is a long stretch, but long stretches can happen over sufficiently long periods of time.
What we’re talking about is an equilibrium process. If a thousand per second are being destroyed while 1,001 per second are being created, then you have growth in the population. Aside from that, there are places on this earth that haven’t seen sunlight in hundreds of millions of years.
Thanks for the cite; interesting reading and worth following, but “bucket chemistry does not a Hollywood bimbo make”.
Sure, if you can detail a mechanism for that which accounts for the parameters noted upstream. So far, I haven’t seen any evolutionary mechanism for any biological process.
Highly improbable. Think more in terms of one reaction every couple of millennia, and it would be closer to being believable.
Thanks for the cite; interesting reading and worth following, but “bucket chemistry does not a Hollywood bimbo make”.
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Specifically what has been detailed is the observation that RNA strands can replicate themselves with no other cellular machinery at all. The article even details the bit-rate of this data transfer for you! If you think you can dismiss it with an offhand comment, that just tells me you’ve already made up your mind that it never happened. Sure, tell me this doesn’t demonstrate that it’s really what happened, but don’t tell me it’s implausible, because the plausibility has been amply demonstrated.
RNA makes DNA. DNA makes proteins. Proteins make simple biological systems. Simple biological systems make complex ones.
Chemical reactions happen much more frequently and rapidly than you seem to understand.
It is perfectly clear that evolution can produce new variability - it is visible in the fossil record, and we can see it in the genomes of many species, including our own. The fossil record demonstrates (for example) the development of a small mammal that is somewhat rabbit-like into the hares and rabbits (which are different species) we see today. A similar progression tracks the migration of nostrils in whales from the tip of the snout to the top of the head. These are not the normal range of variability within a species, but the wholesale change from one species to another. The DNA record is even more indicative. Geneticists can track the development of a gene as it mutates and improves in a population (such as with antibiotic resistance). We can see in the genome how a replication error extends DNA, which then mutates to provide different functionality. We can see inclusions into DNA, which also add functionality. We can also see how unneeded DNA material can be dropped out - mitochondrial DNA does not need the cell membrane structures its free-living ancestor would have had.We are even seeing rapid evolution in hatchery salmon that makes it much harder for them to breed in the wild, and these are genetic changes that can be tracked via DNA sequences. It would only take a few generations of this sort of thing and the hatchery salmon would be a distinct species (unable to breed with wild salmon).
No, it needs something that somewhat works, and evolution makes it work better.
Again, whatever developed was not fully developed - it was probably enough RNA to build a lipid cell coat, and replicate. Thats it, and maybe not even that. Selection pressure, combination and mutation provides the rest.
The development of the complex cell was indeed a trigger for the spread of life. But accepting this as the starting point counters your earlier statement on evolution - all it does is amplify the relative concentration of one particular trait from within the normal range of variability within a species.Those early cells were simple, we see their descendants now - Archaea. These are simple cells that have membranes but no complex internal structure, and they do just fine. And through evolution we have the plurality of life on earth.
This is indeed the case, but not knowing the precise details does not invalidate our understanding that such a process did happen. And the bucket chemistry you complain about gives us some interesting hints, because it does build self-replicating and evolving RNA structures. Coupled with new information about black and white smokers and the lifeforms in them, and we have a range of possibilities for these environments that could provide clues to biogenesis.
Did you actually bother reading the thread you replied to? The answers you seek (or at least some leads) are right there in the first twenty-odd posts.
No, they’re not. I didn’t find them. I want to know how you can get life from non-life. How long before rock, sand and dirt spontaneously become living organisms.
Over the past couple of months I have been working my way through some undergraduate biology texts. There are some things that strike me: the first is how much we know about the functions and processes of biological systems; the second is that, all that we do know about such raises more questions than we have answers for. The more we learn, the more we learn about what we need to learn about.
However, the thing that strikes me most is the fact that all of biology, and its associated branches, is like an inverted pyramid balancing on its apex. The apex is the hypothesis that at some time in the distant past a prototype biological cell appeared, and from this prototype all subsequent life developed.
The significant thing about this prototype is that it contained most, if not all, the information required for all future biological processes and mechanisms. The life forms that have existed, and currently exist, are simply expressions of the information contained within that prototype cell.
The question therefore arises: where and how did this prototype come from?
There are two obvious answers: “God” waved his magic wand and created it; alternatively, it is the result of “materialist determinism” in which a process of random chemical reactions eventually produced the prototype cell.
In my opinion, the “God” explanation fails because it fails to explain where “God” came from. Similarly, the materialist determinist explanation fails due to it being innately ridiculously implausible.
So my question is relating to a third option. Given that the two obvious explanations are non-starters, what other explanation is there for the appearance for the prototype cell?
That should hardly be surprising, since biology is the study of living things. Obviously the study ceases at the point where living things cease to exist
That isn’t true in any conceivable sense. The earliest life forms contained only the information necessary for survival in the environment in which they existed. Any other information that their descendants may have has been produced as a result of evolution.
Honestly, this is like claiming that a pot of ink and a feather contain all the information necessary to produce the Library of Congress. It isn’t true in any sens at all. While the information in the Library of Congress can be produced using just as pot of ink and a feather, the information isn’t in any sense contained within the pot of ink and the feather. The pot of ink and the feather are nothing more than the raw materials from which the information can potentially be produced in the right environment.
In exactly the same way, the first life form didn’t contain the information required for all future biological processes. It was simply the raw material from which processes could have potentially been produced in the right environment. The information wasn’t in any sense contained within the organism, not even in potentia.
I honestly don’t see how this question arises from the preceding claims. Regardless of what qualities the original life form had, the question of how it arose would be just as pertinent. The question doesn’t arise form the qualities you have imbued it with.
While some people believe the former, nobody believes the latter. As has been hashed out at length in this thread, the first cell was the result of evolutionary processes which were anything but random.
The one that scientists accept to be true: that the first cell was the result of evolutionary processes that were directed by competition and natural selection and in no possible sense random.
Appropriate that the old thread terminated on this post, as the Wikipedia article does a better job than Dopers did. I think it’s misleading, though, when it writes
[QUOTE=Wikipedia]
The first living things on Earth are thought to have been single cell prokaryotes.
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Even simple prokaryotes today are much more complex than the “first living things”, which might have been more like RNA viruses. (This is not to say that today’s viruses developed from those early living things.)
A simple creature needs a platform or membrane to retain structure. Coacervates are one such proposed structure, but there are others.
Just as we arose from eukaryotes, which arose from the simpler prokaryotes, which arose from the simpler first living things, so those things arose from ammonia, carbon dioxide, etc. Do those simple molecules have “the information required for all future biological processes” ?
This response really lies at the root of my question. In all of my reading of late, it seems to me that the biological sciences are a mish mash of hard fact, speculation, dogmatism and leaps of faith.
As a case in point, your assertion that the prototype cell is the result of evolutionary processes seems to me to fall into the categories of dogmatism and faith, as opposed to demonstrable fact.
The life sustaining processes of even the simplest cell are of immense complexity; all of which are interconnected and interdependent. Many of these processes are well documented in the texts I have been reading, and I have no argument with that hard science.
However, my objections arise from the explanations as to how these processes came to be. The postulates that this level of complexity came to be by evolutionary processes really require an immense leap of faith, and fly in the face of even simple statistics.
So while I appreciate and acknowledge that your responses are consistent with what I have been reading in current texts, I find that they really do lack in credibility.
Hence my question regarding a third alternative: without invoking “God” or highly improbable “evolutionary processes”, how could a fully functional living cell appear on the scene?
My prior response was directed at this. The simplest cells we know of today have immense complexity. Those cells evolved from simpler cells which no longer exist (and are not visible in the fossil record) because they could not compete with the more complex cells, once they evolved.
Those things are an integral part of all science. That’s not a flaw, it’s a feature.
If you get that impression, I suspect you have misunderstood. Science doesn’t deal in faith, just evidence.
Can you give us an example of something based upon a leap of faith?
Care to elaborate, because it isn’t obvious to me or any other biological scientist.
Well first off we have almost no idea what the life sustaining processes of the first cells were. You are presumably referring to to the simplest extant cells, which are the result of 4 billion years of evolutionary advancement and tell us little about the first cells.
Even amongst living cells, the genome for actual organisms competing in the modern world is less than 500 genes, and the theoretical minimum is less than 200. 500 units is hardly immense complexity and 200 units is surely not complex by any standard.
Just as importantly “immense complexity” is a nearly meaningless term. Even if it weren’t, I don’t quite see what the relevance of it is. The folding pattern of the Appalachian mountains is much more complex than any living cell. I can’t quite see what you think this tells us about the origins of the Appalachian mountains. Prhaps yo can explain?
I also don’t see what relevance “immense complexity” has to your original problem, which is based on a flawed belief that the first cells contained all the information in all currently living cells.
Well, no. That isn’t true on any level. Almost any function of a living cell can be isolated and continue on indefinitely and independently.
Care to show us these statistics? Because I do not believe this is true.
But you haven’t actually explained how, so it’s kind of hard to advance the discussion any further.
At the very least, can you give a specific example of something that you have read that you find incredible and the reasons why?
The first cell was the result of evolutionary processes that were directed by competition and natural selection.
First, your understanding of evolutionary processes and how probable they are is incomplete at best. Your posts keep making the implicit assumption that evolution is directed toward a higher goal. You need to throw out this assumption.
All natural processes work in a fundamentally similar way, whether they involve “life” or non-living things. Your question can be recast as asking how did a few grains of dust and gas know to clump together and form into a smooth ball that orbited perfectly around a central star at just the right conditions to have a habitable atmosphere? Placing “know” into that question seems ridiculous on its face. The dust clumped because of gravity. The orbit occurred because of angular momentum. The inhabitability happened because of chance. We know this because we have examples of planets, dwarf planets, asteroids, comets, and small flakes that were subject to the same physics and same constraints but took other paths.
Getting atoms to form into molecules is the same essential process. We have found molecules of varying complexity, up to and including amino acids, in space, presumably formed just because that’s the way atoms work. In more favorable conditions, many more atoms and molecules have many more chances to form many more molecules as well as more complex molecules. Experiments show that this will indeed happen when outside sources of energy are present. The earth is a hotbed of energy sources and chock full of atoms and molecules to combine. Your statement that this is impossibly improbable is backed by no foundation. They combine because physically and chemically that’s what they do when energy is applied. There is no direction or purpose to this. It does not start at complexity or need complexity to start. Indeed, the simplest possible combinations will form first, but once formed those lead to a new set of simplest possible combinations (albeit of more complexity than the original), which leads to which leads to which leads to. It is as fundamental as erosion. Once more complex molecules exist, they will behave in the way that complex molecules do. One of these ways is replication. Once replication exists, anything and everything else that replies on replication will exist.
The only difference between life and the solar system is that life is not isolated from other life. Even that difference is smaller than it appears. Jupiter certainly cleared out a huge chunk of the solar system through gravitation interactions with anything smaller. If Jupiter were a bit larger or closer to other planets, it may have cleared them out as well. Replicating molecules on Earth work the same way. They clear out competition because they have some advantage. Life may have evolved once, twice, or ten million times. We don’t know. Once life got going it cleared out lesser competitors because it reaches into all niches. We see only one form of life today, but that’s thought to be strictly because all of earth is interconnected. And that explains the frenzy to find live on other planets, because its isolation almost certainly means that it stems from a different beginning.
I know that people don’t like “it just happened” as an answer to life. But every other physical process in the universe can be explained in identical terms. Fusion exists to give the Sun heat because that’s what atoms of that type do at those temperatures and pressures. Light from the Sun reaches the earth along a geodesic curve because that’s how photons move inside the gravity of space-time. UVA light penetrates the atmosphere because that’s what photons of 320 to 400 nanometers do when encountering air. UVB light mostly bounces off because that’s what photons of 280 to 320 nanometers do when encountering ozone particles in the atmosphere. UVC light bounces off completely and thoroughly because that’s what photons of less than 280 nanometers do.
People think of life differently solely because religion and philosophy conditions them to. In terms of physical processes, however, its behavior and origin can be explained, as far as it is known, exactly as every other process in the universe. There is mystery in the details, and wonder as well. But that’s the mystery and wonder of science.
