No, abiogenesis is not a theory as it is not supported by evidence. Instead, it is a hypothesis where we have been able to try some experiments that so far don’t disprove the hypothesis. A Scientific Theory “refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence.”
I don’t need to show any plausible alternatives to prove abiogenesis is not a fact (It’s a hypothesis, but a damn good one.). The supporters of abiogenesis must show that it is “supported by a vast body of evidence.” Of course, they have not and can not do so.
That’s how science works. You need to prove to me that the luminiferous aether hypothisis is valid by a vast body of evidence , not just that I can’t come up with a better idea. In fact, the luminiferous aether hypothesis is a perfect example of why abiogenesis is a hypothesis and not a theory or a fact- it was the ONLY plausible scientific explanation for centuries of how light propagated. Based upon your idea here, that would make it a “fact”. However, the Theory of Relativity (and others) showed that the luminiferous aether hypothesis was in fact completely wrong- even tho it did explain things well and was the only hypothesis the best minds of that era could come up with.
Thus, the luminiferous aether hypothesis as an example disproves solidly the idea “well, my hypothesis explains the situation, and no one has any other plausible alternatives, thus my hypothesis must be a fact”.
Quote:
Originally Posted by Xema View Post
What categories of food do dogs today eat that dogs 10,000 years ago didn’t?
That is just plain wrong to share; TMI. 
What your daughters boyfriend does with her panties should stay between them.
Though I used “theory” above I shouldn’t have. I’m not talking about theories and hypotheses in their technical senses–just things we are justified in believing. Abiogenesis is, for all intents and purposes, an established fact in the sense that we’re justified, by strong reasoning, in believing it took place, and there are no alternatives to it which we are justified in believing took place.
So was luminiferous aether.
I’m not sure why you think that’s relevant. Can you elaborate?
DrDeth I’ve looked back over your posts and I don’t see where we disagree. Who I’ve been disagreeing with is Mijin. “Disagreement” isn’t even the right word–I am just arguing that he’s eliding between different senses of justification in a way that amounts to equivocation. Sometimes he’s relying on facts about justification in the practice of science. Sometimes logical justification. Sometimes inductive justification in general. These are different. (Though of course inductive justification has a large role to play in scientific practice.)
Also, DrDeth, I think you’ve misunderstood me. I said:
But this does not mean (and I don’t believe) that if there are no plausible alternatives to X, then X is a theory. It appears to me that you have misunderstood me to be saying the latter, not the former.
Luminiferous aether= “*by strong reasoning, in believing it took place, and there are no alternatives to it which we are justified in believing took place.” *It was also completely false.
OK, I see what you mean.
Reading back through my posts I can see I was extremely unclear on this point, so I’ll just offer my apologies and move on…
I think that you are confusing two issues. Yes different species share the same or similar DNA sequences, and these days (since fairly recently) the amount of similar sequences* shared by different species is often used as an index of how closely the evolutionarily related those species are.
I do not know if it is true that there are DNA sequences (of meaningful length) that are shared by all species whose DNA has been sequenced. It is possible, but frankly I rather doubt it (I am pretty sure it will be false if we are counting viruses as living things), although there may be some that are shared by all eukaryotes. Certainly your figure of 96% is way too high. I think you are thinking of the similarity between the human genome and that of the chimpanzee, our closest evolutionary relative. We differ more than that from gorillas, let from alone oak trees or bacteria.
However, the DNA evidence that all life has a common ancestor comes not so much from sequence similarities (although they can point towards it, when a lot of such evidence is taken together) but from the fact that all living things on Earth do use DNA (or, occasionally, its close relative RNA) as their genetic material, and more surprisingly, the fact that the DNA of all living things for whom the matter has been investigated - everything from bacteria to oak trees to humans - uses the same genetic code. The genetic code is, as it were, the translation manual by which DNA triplets (sequences of 3 bases/nucleotides) code for the amino acids that make up proteins. So far as we can tell, the code is at least somewhat arbitrary (it did not have to be the way it is) but (with some rare, trivial variations) it is the same for all living things on Earth. I think that if we were to find alien life, then, even if it were like Earth life in using DNA as its genetic material and protein as its main type of workhorse molecule, nevertheless it would be surprising if its genetic code was not at least somewhat different. The fact that all Earth life shares essentially (in most cases, absolutely) the same genetic code is excellent evidence of a common origin for all life, quite regardless of any shared DNA sequences.
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*That is, sequences of meaningful length. As DNA only has 4 “letters” (bases/nucleotides) in its “alphabet” there are bound to be similar short sequences all over the place, just by random chance. I am not sure how long a sequence has to be for its similarity to be considered meaningful for the purposes of inter-species comparison.
And yet, I completely agree with DrDeth and feel that he’s summed up very well what I was saying.
If I’ve differed from DrDeth’s point, please point out where I have done so.
But to summarise again, I think it is flawed reasoning to conclude that something must be true because we cannot think of alternatives.
I agree that, practically speaking, it’s a pretty safe assumption that something like abiogenesis happened. But concluding we know it happened, and even “correcting” those that disagree, is irrational, and contrary to the principle of skepticism.
OK, continuing to demonstrate my ignorance:
When we look at an elephant, a frog or a human, they are all functionally the same. Ie: all of their biological systems have the same functional components, all of which work on more or less the same principles.
The only thing that differentiates an elephant from a frog is the packaging.
So, DNA contains the design specifications for the functional components; attached to that somehow is a specification for the packaging.
This suggests that the process of evolution was a two part process: first the design specification for the functional parts developed; then a second process developed the individual packaging designs.
So the thing that suggests the common origin is the fact(?) that all living creatures have the same functional component specification?
In principle, is my analysis correct?
No, not at all. For starters, frogs and elephants aren’t that far apart. What about insects? Jellyfish? Plants?
I don’t have time to get into it in detail right now.
Isn’t that the essence of what I am getting at?
The packaging is different, but the content is the same.
So, common origin?
No. Your distinction between packaging and content is not valid. Frogs and elephants and humans look different from one another because different stuff is going on inside (or was going on inside as they grew from a fertilized ovum to their adult form). Although most of this stuff is not different, it is enough different to cause one ovum to grow to be a frog, another to grow to be a human, etc.
Perhaps an example is in order. All living things (I’m excluding vira here) produce an enzyme called DNA polymerase, which is one of the enzymes involved in the process of DNA replication. Like with any protein, they all have, somewhere in their genome, a DNA sequence that codes for that protein. But even though all of those enzymes do basically the same job, and they’re mostly similar in structure, the exact structure of that enzyme varies from one organism to another. And even in closely-related species where the enzyme has the same structure, the DNA sequence that codes for it might be a little different (there’s multiple ways each to code for most amino acids).
Now, in at least some cases, you could swap the genes for DNA polymerase between two organisms, and they’d both still be viable. In other cases, that wouldn’t work: If, for instance, you put our polymerase gene in one of those critters that lives in the Yellowstone hot springs, it’d die, because our enzymes will fall apart at those temperatures. And there’s probably some tradeoff in play that would likewise mean that their polymerase wouldn’t work very well in us.
Compared to Mars? The Martian Noachian Period overlaps the Hadean. Or early Venus? Both were at least comparable to earth at the time, without that huge Moon-creating impact event making Earth a bit inhospitable for a time.
No. You’re positing a dichotomy that simply is not supported by evidence. The best I can offer in the way of support is the observation that genes that affect the external phenotype of an organism are generally amongst the most rapidly evolving genes in the genome (reproductive genes are also in this category, interestingly), but that’s not surprising. Generally speaking, a gene that affects your size or color or jaw shape or musculature are probably going to be more important to your survival than a gene that allows a specific biochemical reaction in your liver. This being biology, of course, it’s important to acknowledge that counterexamples to any general statement could easily be found.
But the idea that there are two general “groups” of genes just doesn’t bear up under scrutiny. Instead, you have tens of thousands of individual genes, each undergoing their own selection under whatever pressures may be brought to bear. Every codon for itself, so to speak. This is looking at it from a population point of view, of course, since for an individual organism’s genes, it’s all or none. Hmm. That’s an interesting thought. I may have to ponder that some more. Anyway…
Now, this does all play into the idea of common descent, because once a useful structure evolves, it tends to stick around in later species. Everyone loves to have a kidney, so two animals with kidneys are likely to be more related than one animal with a kidney and one without. But this division into “functional” and “decorative” genes, if I can call it that, just isn’t real.