One can also posit the set of circumstances in which the world was created last Thursday, all our memories and records of scientific work prior to last Thursday are erroneous, and, in fact, there’s no such thing as an atom; we just have all these erroneous memories of experiments which seem to validate the idea that matter is made out of atoms but which never actually took place.
Does that mean the idea that matter is made out of atoms is mere "I can’t think of another way this could have happened"ry, not science? That we should never speak of the atomic theory of matter, and only use the word “hypothesis” instead?
Well, among other things, most of us believe there was no life in the moments just after the Big Bang, what with there being hardly anything yet. You may choose not to believe there even was a Big Bang, of course…
Obviously induction is at the heart of logical reasoning, and the reliability of induction is one of the very few things we have to take as a starting axiom.
But it’s utterly spurious to try to use that as a counter-argument for anything.
I’ve given a specific argument against an assertion. Essentially you’re coming back with “How do we know anything is true”? :rolleyes:
Science is not saying “we can’t come up with another mechanism therefore Abiogenesis”. It’s saying, for abiogenesis to occur what are the likely environment, building blocks and energy inputs that were needed? Did those exist at the end of the Hadeon epoch? Can we produce precursors of life if we duplicate those conditions? Eg it’s making predictions that can be tested empirically.
There is still a lot of questions, but so far it has more evidence than any other possibility.
If you want to argue for something else then you need to provide a hypothesis and evidence thats stronger than the evidence for Abiogenesis.
I’ve also given a specific argument against an assertion. It just happens to be an specific argument which is very widely applicable.
What makes my scenario ridiculous and your time-travelers scenario plausible?
What we can certainly say is this: If there was ever not life, then there was a transition from not having life to having life, which we might call abiogenesis. We might choose not to call it abiogenesis, however, if the means for that transition are that suddenly life appeared time-travelling in from the future; however, nonetheless, there was a transition from not having life to having life.
That is, if there was ever not life, then life arose in a manner which did not depend on chronologically previous life. We may refine this furthermore and say, if there was ever not life, and the transition to having life was not brought about through time-travel, then life arose through a manner which did not depend on either chronologically previous or causally previous life. Or we might not bother bringing up the possibility of chronology and causality diverging till such time as we find our paradigms so shifted as that this seems rather more plausible; no assumption is so absolute as to be unquestionable, but no statement has all its possibly challengeable assumptions explicitly disclaimed either. That’s just not how anyone speaks, unreasonable idealizations of how science works notwithstanding.
Indistinguishable, you’re missing an important point. The hypothesis of Abiogenesis makes falsifiable predictions. Heres one:
If it was the actual mechanism which created life, you’d expect amino acids in the earliest known evolutionary record to be only those that can be created easily from inorganic compounds that were in the environment when life started. And thats actually what has been found:
Thanks for that; so to continue off on this tangent:
If the species can be identified by a “barcode” in the DNA, does this mean that the barcode segment defines the species, and that all life shares a certain proportion of DNA, except for the “barcode” segment?
Could I, hypothetically, extract and mix 'n match the barcode segments, attach them to a chunk of the common DNA, and still produce viable life forms, as defined by the “barcode” segment?
That’s not a prediction that comes from abiogenesis; that’s a prediction that comes from one particular model of abiogenesis. One might also posit, for instance, that life originated based on some other chemicals at first, and then evolved to a point where it was using amino acids, eventually leading to life as we know it. Such a model would still have an abiogenesis event, but would not predict the observation you describe.
Polar Iceman, all living things do have a fair amount of DNA in common, but there are still large differences, too. The segments those labs study are enough to tell one species from another, but they aren’t the only difference between species. If you transplanted those “bar codes”, all that would mean would be that you’d have to look further to tell the difference.
Yes, a model that has empirical evidence behind it. AFAIK abiogenesis is not just a tautology “at one point no life, therefore life came from nothing”, its an attempt to understand the mechanism and process by which that happened. You can test specific models and thats being done.
Is there any actual evidence for any alternative models?
You are arguing that if there are any possible alternatives to X, then X is not a theory.
What Indistinguishable and Chronos are trying to explain to you is that this is incorrect. Instead, if there are any plausible alternatives to X, then X is not a theory.
It is not plausible that the world was created yesterday. It is also not plausible that life started because of time travel.
It’s possible that I’m being a bit too pedantic, here. I agree that the particular model you’re describing is the best-supported one, and certainly much better-supported than the one I described for that example (which has, so far as I know, no support at all). I’m just saying that both of them should be considered abiogenesis models.
Thanks; what I am thinking about is the contention that all life forms have a common origin. I am wondering how this would be shown using DNA analysis.
I understand (and I concede that my understanding comes from reading cheap magazines) that all life shares something like 96% of DNA.
The implication of this is that the remaining 4% is what defines the species.
So, is this remaining 4% embedded throughout the DNA, or attached as a module to some larger structure? Is this larger structure the basis for the contention of the common origin?
Repeating my earlier question: could this 4% be mixed and matched to produce viable life forms?
There is a great degree of commonality in DNA, but the 96% figure is somewhat misleading. In all DNA there are common features, but the common features do vary between species - a good example is the FOXP2 gene. This is important in regulating neural plasticity and has a major influence on speech development in humans and birdsong development in some birds. The human variant of FOXP2 varies by 2 base pairs from a chimpanzee FOXP2, but more in mice and birds. It is a massively small change in DNA, but with massive impacts on development. And it would be wrong to assume that modifying a chimpanzee to give it human FOXP2 would produce a chimpanzee that could speak - the variation in FOXP2 needs to be in the context of all the other genes that seperate humans from other primates.
There is also the “junk DNA” issue. For many years, this was thought to be nonactive - it certainly does not express proteins. But it is becoming clear that junk DNA (which does vary somewhat more between species) regulates expression and DNA folding in ways that we are only just beginning to understand. It is also clear that some junk DNA is actually junk, and has no impact on expression.
So the answer is no, there is no base “Life” DNA package with a custom “Human” module. We keep diverging across our whole DNA, and this is one of the tools geneticists use to determine splitting points. Ongoing changes in DNA occur on an temporal basis, and can be used as a sort of clock tick to point back to a common ancestor and divergence point.
A strong piece of evidence for a common single-cell ancestor is the mitochondrial DNA. At some point, it is probable that a simple singlecelled entity (maybe a eubacterium) paired up with another singlecelled entity (archaea) that produced energy from chemicals in the environment, and the two formed a more efficient symbiotic complex cell. And the DNA studies of complex celled life (like plants, fungi and animals) show that we are all descended from that single merging. It sets the template for our commonality. It doesn’t matter how many times in the ancient past it happened, it succeeded once in evolutionary terms, and all complex life is connected by that. We are essentially the same as mushrooms (kept in the dark and fed on bullshit)
Craig Venter (biologist and human genome sequencer) has turned his eyes on synthetic biology. His team recently bootstrapped an artificial bacteria from synthetic DNA. That was a direct copy of an natural bacteria with some modified junk DNA, but his plan is to isolate the essential bits of DNA to make a working bacteria, and build custom lifeforms using modules. While I support the concept, there are many years of experimentation and analysis to go before this will become a reality. And this is just for a simple single celled bacteria.
UK readers should listen to the latest “The Infinite Monkey Cage” on BBC iPlayer. It involves a discussion of this very topic, with a real evolutionary biologist (as well as physicist Brian Cox, comedian Tim Minchin, and others). It is both funny and informative.
I know that abiogenesis could be used to potentially make predictions. I know that some complex organic molecules have been shown to form spontaneously.
I’d put the odds of abiogenesis on earth at about 98%, and the odds of abiogenesis elsewhere seeding earth at about 1.99%. I’m certainly not saying “I think something else happened”.
I’ll admit it: this started as pedantry on my part; I objected to people matter-of-factly saying “so anyway, we know that abiogenesis happened”. We can’t say that. We mustn’t say that.
But now I’ve seen that a number of people here have some misconceptions about skeptical reasoning.
Trying to invoke last thursdayism as a counter-argument is a particularly desperate strategy.
As is the attempt to redefine abiogenesis to mean any starting of life (when obviously abiogenesis is defined rather more specifically than that; it at least implies a spontaneous start from initially inorganic matter).
You’re not fighting misconceptions. You’re not fighting against a strategy. You’re just wrong.
In this latest post you don’t offer an argument or even an explanation for your view, you simply assert that the people you disagree with are “desperate.” This is incorrect. The people you disagree with are attempting to explain facts to you and you are not listening.
See my previous post. “Possible” alternatives are irrelevant to the question of whether something is an established fact in science or not. What are relevant are “plausible” alternatives. The possibility of biogensesis by time travel doesn’t render abiogenesis a non-fact, because biogenesis by time travel is not plausible.
It is an established fact that the earth goes around the sun. Yet–time travelers could have systematically and subtly screwed around with all our observations on the matter. Maybe the sun goes around the earth after all. Hey it’s possible!
lol
I didn’t bother to repeat my argument because everyone simply conceded the point. It is not necessarily the case that abiogenesis happened, and we as yet have no clear evidence of it.
That’s my point, my only point, and no-one has even tried to dispute it.
What people have tried to do instead is come up with nonsense arguments essentially boiling down to “Well, how do we know that anything is true? Therefore we should be able to state as fact something that we have no proof of yet.”
My hypothetical refuted an abstract logical argument.
It’s quite telling that no-one actually wants to take on that logic, but instead try to frame it as though I am making an empirical claim.
:rolleyes:
The heliocentric model has been verified in a number of ways (although, in the absence of absolute space, all we’re really saying is that the earth is accelerated around the sun. But that’s irrelevant to your or my point).
So given the normal prerequisites for the scientific method, such as assuming that induction is reliable, we have independent grounds to have confidence in that hypothesis.
Abiogenesis however, has not been verified yet. So given the normal prerequisites for the scientific method, such as assuming that induction is reliable, we do not yet have sufficient grounds to have confidence in that hypothesis.
The fact that we cannot think of plausible alternatives is irrelevant from a scientific perspective. All it means is abiogenesis is our working hypothesis. It doesn’t transform it to fact.
You’re treating Chronos’s argument as though it is intended to have the force of logical validity. It was not so intended, so your criticisms are missing the mark.
Much more interesting, does anyone know what the latest is on creating completely new synthetic lifeforms from organic chemistry building blocks? Whats the estimated number of years before that happens?
