Evolution and abiogenesis

[Skeptic Ginger]

... The main issue to be revisited, is whether retrospective predictions ('post-dictions'), made from the principles of Evolution Theory, (context = Earth and 'Earth-life'), carry 'weight' when considering generalised, complex, pre-biotic' molecular behaviours. We should note that such 'post-dictions' are as yet, untested outside of their 'natural' physical and environmental contextual bases, (which produced them), ie: Earth and Earth-life. (Meaning exo-planetary bodies).

Theory and observation are intertwined in Evolution theory and we have empirical definitions that are operational and objective and do not change, but we also have a theoretical understanding of how these things, like self replicating organisms, should behave, and that is part of how we understand what these things are. However, it's that latter part, the theoretical understanding, that typically changes in science, (eg: just look at how our theoretical understanding of time, space, electrons, etc has changed over our lifetimes). This does not mean these concepts are not scientific concepts, it means they are, like everything in science, contextual, provisional, and subject to revision so I say, we should make the same allowance in the case of Evolution theory and permit it to examine, and maybe revise, its original, singular natural contextual basis, (aka: Earth and 'Earth-life'). This may, or may not, present a reason for revising Evolution's theoretical 'post-dictions' made about Abiogenesis, but we should at least, consider that it might, before dismissing, outright, any possible distinctions between Abiogenesis and Evolution.

This is gobbily-gook. I've read this and your earlier posts wondering if I was missing the point. But there is nothing here. This stuff sounds like contemplating the universe on too much wine and pot.

 

[RecoveringYuppy]

Please cite the LD50 for pot.

 

[marplots]

Please cite the LD50 for pot.

Well, LD50 is going to be an estimate, since we don't actually want to kill people to find out. With that in mind: 31 joints, based on HCN. Other compounds in marijuana smoke may give different numbers, I just picked out HCN.

(Based on LD50 inhaled for HCN of 50mg and this paper: http://www.ukcia.org/research/ComparisonOfSmoke.pdf and using worst case.)

 

[WhatRoughBeast]

Please cite the LD50 for pot.

From http://www.ncbi.nlm.nih.gov/pubmed/23796481

The minimum lethal oral dose for dogs for THC is more than 3 g/kg. Although the drug has a high margin of safety, deaths have been seen after ingestion of food products containing the more concentrated medical-grade THC butter.

 

[Skeptic Ginger]

Please cite the LD50 for pot.

Why? You need not overdose to contemplate the universe.

 

[RecoveringYuppy]

Why?

Couldn't think of any other basis for "too much".

 

[Perpetual Student]

But why start with the non-evidenced hypothesis that those mechanisms had an abrupt onset?

You are assuming I have started with that hypothesis, which is not correct. These two mechanisms may very well have been synergistic and overlapped for millions of years; nevertheless they are distinct. It would also appear that once self replication was established and natural selection took traction, abiogenesis was marginalized as a significant mechanism for the continuation of life. As I'm sure you know, there are many candidates for the mechanism for abiogenesis; replication and metabolism are key elements of those mechanisms but natural selection by virtue of random errors is not a necessary component.

 

[Skeptic Ginger]

Couldn't think of any other basis for "too much".

You are mistaken. "Too much" was not involved. Perhaps you've never contemplated the universe while high.

 

[Skeptic Ginger]

You are assuming I have started with that hypothesis, which is not correct. These two mechanisms may very well have been synergistic and overlapped for millions of years; nevertheless they are distinct. It would also appear that once self replication was established and natural selection took traction, abiogenesis was marginalized as a significant mechanism for the continuation of life. As I'm sure you know, there are many candidates for the mechanism for abiogenesis; replication and metabolism are key elements of those mechanisms but natural selection by virtue of random errors is not a necessary component.

The fact you hypothesize they are distinct is what I'm talking about.

I don't get it, it's like evolution theory defenders have been defending against the 'god started it' argument for so long they've adopted the 'abiogenesis is different from evolution theory' as if it were an established fact. When you assert, "natural selection by virtue of random errors is not a necessary component", are you also allowing for the hypothesis that it might be a component nonetheless?

 

[Perpetual Student]

The fact you hypothesize they are distinct is what I'm talking about.

I don't get it, it's like evolution theory defenders have been defending against the 'god started it' argument for so long they've adopted the 'abiogenesis is different from evolution theory' as if it were an established fact. When you assert, "natural selection by virtue of random errors is not a necessary component", are you also allowing for the hypothesis that it might be a component nonetheless?

I am not aware of any proposed abiogenesis mechanism that requires natural selection by virtue of random errors of replication, but I'm always more than willing to learn if there is such a proposed mechanism. In any case, yes, I agree it might be a component, but I do not currently see how that might work.
Think about it; there can be no natural selection without replication, but replication can readily be demonstrated without natural selection.
It would appear to me that there is a grey area (not an abrupt line) between the two mechanisms. FTR: no deities are required.

 

[jimbob]

At the core of the theory of evolution are the concepts of imperfect self replication and natural selection. Unless abiogenesis can be shown to involve those same two mechanisms, it must be considered to be a distinct process.

I think that any plausible theory of abiogenesis will have to include proto life.

There's some evidence that we might have got that far already in the latest approach to estimating the genetic makeup of LUCA.

New Scientist's take on this is below

https://www.newscientist.com/articl...tor-of-all-life-on-earth-was-only-half-alive/

My reading is that some of the functions of respiration (namely the maintenance of an ionic gradient) were not within the control of LUCA but just a function of its environment.

 

[jimbob]

My longer take on this

I disagree.

The classic definition of life is that living organisms exhibit the following behaviours

• Nutrition
• Respiration
• Excretion
• Growth
• Reproduction
• Movement
• Response

There is absolutely no reason to suppose that there was a soup of organic compounds that exhibited none of these and then they came together to exhibit all.

It looks to me as though reproduction would come first - after all we can replicate RNA/DNA chemically already. Once that is kicked off with an electrochemical gradient in place of the internal Respiration, Nutrition, and Excretion, then these would be subject to evolution - this is little difference from a virus hijacking a cell to do the same thing, and viruses are not considered to be alive of themselves.

Some of the self-replicating molecules would be better at replicating in groups with other types of molecules, and whilst far from being alive, there would be evolution of these groups of molecules. If you then get a situation where one group of molecules makes a membrane that keeps a population of molecules together, then you are pretty much of the way to cells. You would have discrete populations of molecules in discrete packages that reproduce when there is an external electrochemical gradient, but doesn't share the other characteristics of life.

If one of these packages then develops its own way of maintaining the electrochemical gradient, you have respiration and excretion as well as nutrition. It's just a matter of time before the rest arise then.

 

[Emily's Cat]

What I have in my head is traditional evolution a subset of a grander picture about complexity arising far from equilibrium, anchored not in "life," but in plain old chemistry, reaction rates and products. Which means principles applicable across the spectrum.

I agree that the process by which evolution occurs can be generalized to things outside of biology. But I also think that within the context of this thread, we're explicitly limiting it to biological evolution. Personally, I think that when we extend that process beyond life it will probably need a new name.

 

[Emily's Cat]

From http://www.ncbi.nlm.nih.gov/pubmed/23796481

Holy cow. If my google conversion and math are correct... a 150lb person would need to ingest about 200 grams of THC to die from it. That's a LOT. I mean, a HUGE amount of THC. I know I'm a lightweight and all, but at about 25 mg of THC, I forget how to make words form with my mouth, and generally end up couch-locked for several hours. 200 grams is... well... about 8000 times as much as gets me glued to the earth.

Couldn't think of any other basis for "too much".

I'm gonna say my state at 25mg counts as "too much"

 

[Emily's Cat]

I am not aware of any proposed abiogenesis mechanism that requires natural selection by virtue of random errors of replication, but I'm always more than willing to learn if there is such a proposed mechanism. In any case, yes, I agree it might be a component, but I do not currently see how that might work.
Think about it; there can be no natural selection without replication, but replication can readily be demonstrated without natural selection.
It would appear to me that there is a grey area (not an abrupt line) between the two mechanisms. FTR: no deities are required.

This is not my field, so I might be talking out of my rear.

To me, I've always envisioned evolution as a process. It has several factors involved, but the biggest by far is selection - both natural and sexual. Now sexual selection is clearly limited solely to those objects that reproduce sexually... so far that's only living things, but hey we could find something someday I guess.

The natural selection part, however, has to do with probabilities. It has to do with how likely a particular formation is to persist within the current environment. This process, this probabilistic component of the persistence of formations, would apply regardless of whether an object is classified as living or not. The fact that certain molecules only form under certain conditions, and come apart under other conditions, is part of that same process. It's the equilibrium value of an object given a set of conditions... and when those conditions change, so does the equilibrium value. Thus, over time and changing conditions, the formation of the objects will also change - sometimes quickly, but often very slowly. The formation of Earth from a glob of goo orbiting a sun is the approach to an equilibrium value for that glob of goo. It's more stable than the glob of goo. Evolution then, would be the process that acts in opposition to entropy. It's the process by which order occurs from disorder.

Abiogenesis, on the other hand, is a taxonomic bright line along the spectrum of objects. Abiogenesis is the set of characteristics that define the moment that a thing changes from being non-life to being life. In that respect, it's no different from the taxonomic definition that allows Pluto to lose it's place as a planet. Pluto lacks some of the characteristics that we've defined as belong to a planet. Similarly (if I understand correctly), viruses lack some of the characteristics that we've defined as belong to life. They're pretty darn close - they tick many of the boxes... but ultimately they fall just a tiny bit short. Just like Pluto falls a tiny bit short of being a planet.

Abiogenesis and Evolution end up being talked about together frequently... but ultimately they're not the same thing. No more than the process of planet formation is the same as the definition of what constitutes a planet versus a dwarf-planet. One is a process by which a change occurs; the other is a taxonomy.

 

[MuDPhuD]

The fact you hypothesize they are distinct is what I'm talking about.

I don't get it, it's like evolution theory defenders have been defending against the 'god started it' argument for so long they've adopted the 'abiogenesis is different from evolution theory' as if it were an established fact. When you assert, "natural selection by virtue of random errors is not a necessary component", are you also allowing for the hypothesis that it might be a component nonetheless?

Consider:
At some point during the Hadean a polymer (RNA?) with the capacity for imperfect self replication was formed in an aqueous solution.

There need be no encapsulation (membrane), there is no need for specifying the length of the polymer, there is no need for a genetic code (no translation), there is no need for metabolic pathways. There is only an aqueous solution with necessary raw materials and the minimal necessary polymer for imperfect, but high fidelity self reproduction. If the reproductive fidelity is poor, reproduction will not continue, if perfect it will not have the capacity to introduce variation (although an initially perfect replicator could acquire variation by introducing modified raw material!).

It may have occurred in fits and starts, over an indefinite period of time, but once this replicator is formed in the presence of sufficient raw materials evolution has begun. I agree, it would be very difficult to call this replicating molecule "living", but evolution would have begun, possibly with a single strand of self replicating polymer. All (most?) of the attributes of life as we know it would be added over a few hundred million years, but there is a definite starting moment where evolution of the replicator begins.

Before this moment there is no evolution as we know it, there is only chemistry. To be sure if we want to tweak the definition of evolution to mean simply "change over time" then we could apply the term to the prebiotic soup and its altering chemistries on the early earth. On the other hand, if we want to define evolution as requiring the presence of an evolving imperfect self replicator then there is a point of beginning.

At some point after the replicator had acquired enough recognizable characteristics it would be obviously "alive", but it is difficult to pin down at exactly what point that transition was crossed.

So, there is a dividing line between pure chemistry and evolving chemistry, and an uncertain boundary between evolving chemistry and evolving life. Evolution with a capital E, as I understand it, applies only to what happens after the origin of the imperfect self replicator, but for several hundred million years this would have been difficult to recognize as "alive".

 

[Hlafordlaes]

... So, there is a dividing line between pure chemistry and evolving chemistry, and an uncertain boundary between evolving chemistry and evolving life. Evolution with a capital E, as I understand it, applies only to what happens after the origin of the imperfect self replicator, but for several hundred million years this would have been difficult to recognize as "alive".

Sounds good to me.

 

[Perpetual Student]

Consider:
At some point during the Hadean a polymer (RNA?) with the capacity for imperfect self replication was formed in an aqueous solution.

There need be no encapsulation (membrane), there is no need for specifying the length of the polymer, there is no need for a genetic code (no translation), there is no need for metabolic pathways. There is only an aqueous solution with necessary raw materials and the minimal necessary polymer for imperfect, but high fidelity self reproduction. If the reproductive fidelity is poor, reproduction will not continue, if perfect it will not have the capacity to introduce variation (although an initially perfect replicator could acquire variation by introducing modified raw material!).

It may have occurred in fits and starts, over an indefinite period of time, but once this replicator is formed in the presence of sufficient raw materials evolution has begun. I agree, it would be very difficult to call this replicating molecule "living", but evolution would have begun, possibly with a single strand of self replicating polymer. All (most?) of the attributes of life as we know it would be added over a few hundred million years, but there is a definite starting moment where evolution of the replicator begins.

Before this moment there is no evolution as we know it, there is only chemistry. To be sure if we want to tweak the definition of evolution to mean simply "change over time" then we could apply the term to the prebiotic soup and its altering chemistries on the early earth. On the other hand, if we want to define evolution as requiring the presence of an evolving imperfect self replicator then there is a point of beginning.

At some point after the replicator had acquired enough recognizable characteristics it would be obviously "alive", but it is difficult to pin down at exactly what point that transition was crossed.

So, there is a dividing line between pure chemistry and evolving chemistry, and an uncertain boundary between evolving chemistry and evolving life. Evolution with a capital E, as I understand it, applies only to what happens after the origin of the imperfect self replicator, but for several hundred million years this would have been difficult to recognize as "alive".

 

[jimbob]

Consider:
At some point during the Hadean a polymer (RNA?) with the capacity for imperfect self replication was formed in an aqueous solution.

There need be no encapsulation (membrane), there is no need for specifying the length of the polymer, there is no need for a genetic code (no translation), there is no need for metabolic pathways. There is only an aqueous solution with necessary raw materials and the minimal necessary polymer for imperfect, but high fidelity self reproduction. If the reproductive fidelity is poor, reproduction will not continue, if perfect it will not have the capacity to introduce variation (although an initially perfect replicator could acquire variation by introducing modified raw material!).

It may have occurred in fits and starts, over an indefinite period of time, but once this replicator is formed in the presence of sufficient raw materials evolution has begun. I agree, it would be very difficult to call this replicating molecule "living", but evolution would have begun, possibly with a single strand of self replicating polymer. All (most?) of the attributes of life as we know it would be added over a few hundred million years, but there is a definite starting moment where evolution of the replicator begins.

Before this moment there is no evolution as we know it, there is only chemistry. To be sure if we want to tweak the definition of evolution to mean simply "change over time" then we could apply the term to the prebiotic soup and its altering chemistries on the early earth. On the other hand, if we want to define evolution as requiring the presence of an evolving imperfect self replicator then there is a point of beginning.

At some point after the replicator had acquired enough recognizable characteristics it would be obviously "alive", but it is difficult to pin down at exactly what point that transition was crossed.

So, there is a dividing line between pure chemistry and evolving chemistry, and an uncertain boundary between evolving chemistry and evolving life. Evolution with a capital E, as I understand it, applies only to what happens after the origin of the imperfect self replicator, but for several hundred million years this would have been difficult to recognize as "alive".

Yes, the last three paragraphs are key. As soon as you have imperfectly self-replicating systems in a finite environment, you have evolution.

Life also requires growth, respiration, nutrition and excretion (I'll ignore the response to stimuli and movement for now. as I'd say those would come slightly later).

Proto life could have analogues of nutrition, excretion and respiration - in fact it seems that LUCA might have been in this situation.

 

[JeanTate]

This is gobbily-gook. I've read this and your earlier posts wondering if I was missing the point. But there is nothing here. This stuff sounds like contemplating the universe on too much wine and pot.

I disagree.

I think what SS is trying to say is rather unexceptional, kinda putting a pretty-much-everyone-agrees boundary, sorta, on the topic. But the way it's expressed is, I agree, hard to follow. That's why I tried to understand it, by changing the context (see my 'purple post', above).