Originally posted by Halitose Take all the requirement for a fuctioning single-celled organism, take random chance and add the two together and see if it is statistically possible. DNA is a good start as it is the molecule which regulates the functionality of a cell.
How does one "add together" random chance and these requirements? Can you describe the inferential process here?
Originally posted by Halitose I can boast a rudimentary knowledge of abstract algebra. 😛
If you start defining a new sort of addition in terms of concrete calculations as suggested above, I wouldn't boast too much.
Your calculation isn't even well-defined. What are the right positions and sequences? How do you know that the ones you would name have the property of being uniquely right?
Originally posted by Halitose For a start, I'd suggest calculating the odds of 100,000 base pairs randomly being in the right sequence.
You are confused here. First, there is no reason to think that the location of the base pairs are fully independent of one another. Given that subsets of these base pairs will all come together, we should be calculating conditional probabilities rather than independent probabilities. Second, there is no reason to think that there was only one chance to get the base pairs into the "right sequence". Presumably, the precursors of this DNA chain were continuously forming longer chains, breaking apart, etc. Consider coin flips. What are the odds of getting 100 heads in a row in some series of coin flips? You can't answer that question unless you specify how many individual coin flips are in the series. If you flip the coin only 100 times, the probability will be small. If you flip the coin a trillion times, the probability will be much larger. Third, you have given us no reason to think that there is only one "right sequence". Just because some ancient bacterium had some particular set of base pairs doesn't mean that some alternate set of base pairs could not also constitute a "right sequence".
Originally posted by bbarr You are confused here. First, there is no reason to think that the location of the base pairs are fully independent of one another. Given that subsets of these base pairs will all come together, we should be calculating conditional probabilities rather than independent probabilities. Second, there is no reason to think that there was only one chance to get ...[text shortened]... sn't mean that some alternate set of base pairs could not also constitute a "right sequence".
Sure. We can go on the assumption that the DNA was continuously forming and reforming. We can have those coins flipping for a couple billion years.
Originally posted by Halitose Abiogenesis: The supposed development of living organisms from nonliving matter.
What are its requirements? Is it statistically possible?
Here is what I've written on abiogenesis in the past:
The Earth probably formed about 4.5 billions years ago. It was a hot, inorganic ball of rock with oceans and an atmosphere containing nitrogen, carbon and hydrogen atoms in some gaseous form or another, but no oxygen gas (O2). I don't really know what molecules these atoms were organized into, but it doesn't really matter. When gasses of made up of these elements are exposed to lightning, ultraviolet light or heat, simple organic molecules will form, as demonstrated by Stanley Miller and Harold Urey in 1953, and I believe others since.
Amino acids, short proteins, nucleotides, ATP (and probably other nucleoside triphosphates), and other molecules characteristic of living things are some of the organic molecules that have been observed to form in laboratory recreations of these conditions. In addition, we know from present day meteorites that such meteorites often cary such simple organic molecules with them. Such molecules are vulnerable to uv radiation exposure from the sun (no ozone layer yet) but some places, like tidal pools hidden under rocky shelfs, would be shielded from uv exposure.
Some such pools would have had ocean water splashing into them during high tide, bringing with it the organic molecules in it, and during low tide some of the water in the pool might have evaporated. By this or some other mechanism pools of water sheltered from uv radiation would become highly enriched in the organic molecules. As there was not yet any life and no free oxygen, these molecules had no environmental influences that would break them down.
When organic molecules like these are placed in concentrated enough solutions, they spontaneously react to form more complex organic molecules, such as RNA.
RNA molecules with all kinds of random sequences would spontaneously form. Now we know that RNA, like proteins, folds into specific configurations depending on the sequence of bases it is made up of. Sometimes the folded RNA is catalytic; that is, it makes an enzyme. Such RNA enzymes are called ribozymes.
Now RNA, like DNA, already has an obvious mechanism by which it could replicate itself. This is the point at which substances began to catalyze the synthesis of smaller molecules into copies of themselves; that is, they reproduced. Being genetic material with no proofreading systems with the potential to be exposed to uv light, such RNA chains began to mutate into chains with slightly different base sequences. Any of these which folded into enzymes that catalyzed their own reproduction would begin to out compete the other RNA chains in terms of reproduction and using up the raw materials for reproduction. The process of evolution has begun, even before life existed.
Now, it's been shown that amphipathic molecules like phospholipids will tend to aggregate and form one of three different formations depending on the conditions; micelles, solid molecular sized balls of phospholipid molecules, a bilayer, or flat sheet (which would need to be anchored on the edges away from water), or a combination of the two, a vesicle. A vesicle is lipid bilayer bent into a spherical shape and closed upon itself. Such vesicles trap water and the contents of water in their cavities when they form. Small molecules can pass through the phospholipid bilayers of such vesicles far more easily than larger molecules.
Some of these vesicles probably formed around RNA which was already evolved into a form that catalyzed it's own reproduction quite effectively. Such RNA still had access to the small molecules it needed as raw material for self reproduction, but large molecules that might damage it or otherwise interfere were kept out. The RNA would reproduce and reproduce, and the new ribozymes wouldn't be able to get out of the vesicle. Maybe more than one kind of self replicating RNA would get trapped inside the vesicle and begin to reproduce.
This stage of prebiotic evolution is known as the protocell. Such protocells could collect more and more phospholipid molecules and keep reproducing the RNA inside, causing the protocell to grow.
At this point, a number of the characteristics of life have come into being. The protocell has begun to aquire and use materials and energy from it's environment and to convert them into different forms. It was growing. It had the capacity to evolve. And, once these things grew big enough, and possibly with the help of the ribozymes inside, they would divide. This is reproduction of the entire protocell.
Now, sometimes more than one molecule of RNA would get trapped inside and begin to self-replicate; sometimes some copies of the RNA inside the protocell would mutate into different forms. In this way different enzymes would come into being, providing a more varied environment inside the protocell. Sometimes these various chains of RNA would begin to specialize into symbiotic relationships, helping one another reproduce and do other things.
As you can see, it makes perfect sense based on much experiment that such a pattern of change from inorganic, simple molecules to complexity in the form of protocells could plausibly come into being. Any entropy lessened in the formation and reproduction of these ordered objects would be compensated for by breakup of nucleoside triphosphates. This effectively changes sunlight or other ordered forms of energy to heat, which I think counts as increased entropy. So, unlike what some creationists suggest, the Second Law of Thermodynamics is not broken by this proposed mechanism.
Some of these ribozymes would begin to assemble amino acids into short chains through catalysis of dehydration reactions. Once proteins were being formed, similar evolution would produce protein catalysts or enzymes. At some point some RNA would catalyze the formation of the more stable DNA molecules, which would take over as the genetic material of these protocells.
At this point we pretty much have a primitive cell, or something close to it. Life is a poorly defined word, so there isn't any exact moment at which one could say it has been crossed. It's more of a long process full of small changes that caused the protocell - not alive - to the cell - alive. The cell then began to evolve, but that's beyond the scope of the question asked here.
Originally posted by Halitose <halitose sits in corner licking his wounds>
Can we agree on the hypothetical state of this first living cell. Most evolutionists agree that the very first cell of life was a simple bacterium. Current bacteria DNA has about 128 million base pairs. However, scientists claim to have found ancient fossils of bacteria which they claim to only have 500,000 ba ...[text shortened]... ossible for the earliest bacterium to have survived with as little as 100,000 base pairs of DNA.
The only number of base pairs (as opposed to genes) I've been able to find in my 10 minutes of looking was this:
The minimum cellular genome is estimated by various techniques at about 562,000 nucleotide pairs, close to the 580,000 nucleotide pairs of Mycoplasma genitlium, the simplest life form known today.
Originally posted by Halitose For a start, I'd suggest calculating the odds of 100,000 base pairs randomly being in the right sequence.
This is entirely the wrong approach, as bbarr pointed out. While life may have certain requirements, self replicating nucleic acid polymers do not share those requirements and could evolve into life.
Originally posted by Nordlys It doesn't have to be a deistic conception of god either. Many (I guess most, although I don't have numbers) Christians adhere to evolution, but they are certainly not deists.
Yes, but that would involve god being the inspiration and guiding force behind evolution. I had chosen a diestic god to separate creation from evolution, with god doing the creating and naturalistic evolution taking over from there.
Originally posted by Halitose For a start, I'd suggest calculating the odds of 100,000 base pairs randomly being in the right sequence.
How do you come to the conclusion of randomness, since pairs are 4 acids put together 4 ways and the bases are groups of 3 of the pairs that follow the same bonding rules and this implies that the groups also can only bond in a limited number of ways.
It may well turn out that most of the randomness has been eliminated at quantum mechanical levels.
Originally posted by rwingett Yes, but that would involve god being the inspiration and guiding force behind evolution. I had chosen a diestic god to separate creation from evolution, with god doing the creating and naturalistic evolution taking over from there.
I am not sure what exactly the position of Christians adhering to evolution is on this matter (and I am not sure there is one position), but you may be right that most of them believe that evolution is inspired and guided by God. However, this is not necessarily implied in a theistic approach. Natural processes could run entirely on their own even if the god who did the creating would still be present and active in some ways. There are examples in the bible where something happens which goes against natural law due to God's intervention, but many Christians see those things as metaphors for something which happened on a spiritual level.
Abiogenesis
15 Sep '05 19:29
Back to Top