Before biological evolution, there was probably chemical evolution.
Deep under the oceans, there are hot water vents that build up into complex chemical environments fed by reactive chemicals from the earths crust (H[sub]2[/sub]S and the like). These vents have been observed to form things like black smokers (made of sulphides) and white smokers (silicates, carbonates) with microcavities that trap chemical activity and can form complex hydrocarbon chemicals due to chemical gradients. If a microcavity ended up lined with lipids, other chemicals including proto-RNA and enzymes could be encapsulated and trapped into a self-sustaining cell. It is possible that these environments gave rise to the first simple forms of life (probably Archaea, simple nonnuclear cells that use chemical sources to provide energy). Eventually more complex cells evolved, and (in a happy accident) a larger cell included an Archaea, and complex cells with an inbuilt energy source (mitochondria, chloroplasts) developed.
With a separate energy source, cells could develop that did not rely so closely on the extreme chemical environment of the vents, and so the oceans were populated, the atmosphere changed with the release of oxygen, and life then changed with it.
That is another hypothesis of abiogenesis, anyhow.
The point is “I can’t think of another way this could have happened, therefore abiogenesis” is not science.
What if life was started by humans going back in time and putting it there (obviously this causal loop leaves open various ontological questions, but no more so than a non-looped reality).
Abiogenesis is the leading hypothesis because we have seen evidence that relatively complex organic molecules can form spontaneously. Scientists shouldn’t assume a hypothesis into a theory.
I think there’s a good argument to be made that earth during the Hadeon epoch was still a better environment for life than most other places in the Solar System.
Any precursors to life would be in sea water, be microscopic, and easily accidentally swallowed by large organisms.
It’s not just that though. Besides the Earth being geologically much different now, the environment has also been fundamentally altered by life. For example, the atmosphere has a lot more oxygen now than it used to. Modern levels of oxygen would be toxic to those life forms.
Even if a primordial life form could avoid being consumed or destroyed, it would have to be very different than what originated billions of years ago because the geology and environment of Earth have radically changed.
The plural of hypothesis is hypotheses. The terms ‘theory’ and ‘hypothesis’ may have similar meanings in this context, but they are not synonyms as you seem to imply by your seamless transition from the first sentence I’ve quoted here to the one after it.
To assert that something is a ‘theory’ and then to assert that it is a ‘fact’ is a contradiction. These terms are not synonymous and something can, at best, be one or the other. This is not a legitimate use of the phrase ‘in other words’. Writing a word all in upper case does not add weight to your opinion (if anything it tends to have the opposite effect) or provide extra insulation from your views being challenged or corrected.
The adjective ‘solid’ is meaningless in this context. ‘Testable proof’ does not mean anything. You can test a hypothesis, you can assess evidence and you may in some contexts arrive at proof of something or other. However, you cannot test proof.
There is no reason to capitalise the ‘H’ in ‘hypothesis’. The terms ‘scientific hypothesis’ and ‘educated guess’ are not synonymous. A hypothesis is an attempt to provide an explanation for a given set of observations, and it can be used as the basis for predictions checked via scientific experiment. An educated guess is an estimate based on past experience made in lieu of reliable data.
You know that the Straight Dope is supposed to be about fighting ignorance, not spreading it around more thinly… right?
This line of reasoning works if we presume that large organisms regularly swallow a high percentage of all sea water and pass it through their digestive systems.
Not sure why you needed to dissect his post like that, but I thought it was actually pretty good, and made an important point about the difference between a theory and a hypothesis, wrt a previous post about Abiogenesis. I didn’t see that he was saying the two words were synonyms. Quite the opposite.
We can quibble about whether a theory is considered a “fact”, and while they are technically different things, it would be better if people used them as synonyms in lay speech than the current situation where most people use hypothesis and theory as if they were synonyms.
I made it clear that a “Hypothesis” is not the same as “Theory.” A scientific hypothesis is a educated guess which is not currently supported by evidence. Abiogenesis is a scientific Hypothesis, not a scientific Theory. A scientific theory is for all intents and purposes a fact. The “Heliocentric Theory” is a FACT, the Earth does go around the Sun.
According to the United States National Academy of Sciences, The formal scientific definition of theory is quite different from the everyday meaning of the word. It refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. Many scientific theories are so well established that no new evidence is likely to alter them substantially. For example, no new evidence will demonstrate that the Earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the Earth is not divided into solid plates that have moved over geological timescales (the theory of plate tectonics). One of the most useful properties of scientific theories is that they can be used to make predictions about natural events or phenomena that have not yet been observed.[10]
Your little corrections and comments are hardly helping in the fight against ignorance. :rolleyes: “There is no reason to capitalise the ‘H’ in ‘hypothesis’” – you do know you spelled “capitalize” wrong?
Your first sentence doesn’t make any sense, because abiogenesis doesn’t refer to a way that something happened. We don’t know how abiogenesis happened; we just know that it did happen. Maybe it happened in the way described by the current prevailing hypotheses. Maybe it happened almost like that, but with a few subtle differences. Maybe it happened because the Flying Spaghetti Monster touched the seas with His noodly appendage. We don’t know, and I’m not really even sure how we could find out for sure. But it happened somehow.
As for the second sentence, about time travel, well, yes, I suppose that would be an alternative to abiogenesis, but once you start down that path, it’s a short step to Last Thursdayism. When your best alternative to an idea is time travelers, it’s safe to consider that idea established fact.
No, it’s not equivalent to Last Thursdayism, and I think you’ve missed the point.
The point is this: you should never make assumptions about what is “obvious”. It’s interesting because of course Vitalism (which is very nearly the opposite of abiogenesis), was itself was based on common sense and intuition.
The counter-example I gave may be ridiculous but that doesn’t matter. Think of it as a thought experiment to try to refute a general argument. The reality may be something which neither of us could have thought of.
When you have eliminated the impossible, whatever remains, however improbable, must be the truth – was something said by a fictional character, which doesn’t work in practice.
OK, give me an alternative that’s actually plausible, then. “Once there was not life, and now there is life, and therefore at some point something not-life must have turned into something that is life” is about as straightforward an argument as you can get.
Chronos, all I can do is repeat the argument I have just given, because your point ignores what I just said.
If I can posit a set of circumstances in which the logic doesn’t hold, then the logic doesn’t hold. And we should disregard any conclusions made with that logic.
The set of circumstances doesn’t need to be plausible any more than it needs to be plausible that you can race a beam of light, or have infinite monkeys use infinite typewriters.
