MarkE
2020-09-08 14:32:53 UTC
An “everything-first” model of origin of life is proposed by the author [1] of a New Scientist article [2] on this basis:
“Many ideas have been proposed to explain how it began. Most are based on the assumption that cells are too complex to have formed all at once, so life must have started with just one component that survived and somehow created the others around it. When put into practice in the lab, however, these ideas don’t produce anything particularly lifelike. It is, some researchers are starting to realise, like trying to build a car by making a chassis and hoping wheels and an engine will spontaneously appear.” And, “However, biochemists have spent decades struggling to get RNA to self-assemble or copy itself in the lab, and now concede that it needs a lot of help to do either.”
As an aside, note the invocation of irreducible complexity by a non-ID proponent.
“The alternative – that life emerged fully formed – seems even more unlikely. Yet perhaps astoundingly, two lines of evidence are converging to suggest that this is exactly what happened. It turns out that all the key molecules of life can form from the same simple carbon-based chemistry. What’s more, they easily combine to make startlingly lifelike ‘protocells’.”
The first challenge is finding a plausible natural scenario for the simultaneous production of building blocks for membranes, genetic polymers, and proteins. This possibility is cited:
“By combining a similar organic compound called cyanamide with other simple chemicals, John Sutherland at the MRC Laboratory of Molecular Biology in Cambridge, UK, has created nucleotides, the building blocks of RNA. The reaction requires “ Life’s key molecules can form together thanks to ‘Goldilocks’ chemistry” ultraviolet light, heating and drying, and wetting with water. Sutherland’s team found that the same starting chemicals can also make the precursors of amino acids and lipids. “All the cellular subsystems could have arisen simultaneously through common chemistry,” he concluded. The key is what Sutherland calls “Goldilocks chemistry”: a mixture with enough variety for complex reactions to occur, but not so much that it becomes a jumbled mess.”
The second challenge is their assembly. The author makes this statement: “What’s more, they easily combine to make startlingly lifelike ‘protocells’.”
I’m interested in two aspects of this assertion: “easily combine” and “startlingly lifelike ‘protocells’”.
It is demonstrable that spherical membranes (vesicles) can form spontaneously: “If these lipids were subsequently added to salt water and shaken, they formed spherical blobs with two outer layers of lipids, just like cells.”
Membranes, therefore, can be said to “easily combine”. What about genetic polymers and proteins?
The author has already answered this question with respect to RNA: “However, biochemists have spent decades struggling to get RNA to self-assemble or copy itself in the lab, and now concede that it needs a lot of help to do either.” The appeal to the “everything-first” hypothesis is based on the claim that naked RNA self-assembly and copying doesn’t work. But suddenly we’ve jumped to “easily combining” a lipid membrane around some RNA, self-assembled and even copying itself.
“Szostak’s group has even persuaded RNA to copy itself within protocells.”
Szostak’s work with RNA template copying in protocells requires magnesium ions for nucleotide assembly on the existing RNA, and uses a citrate molecule to clamp on to a magnesium ion preventing it from reacting with a fatty acid but still allowing it to interact with the RNA [3].
It's important to read the fine print: “Despite lacking any of the complex cellular machinery, they can reproduce by dividing to form daughter protocells. “What’s missing is a replicating genetic material,” Szostak says.” So we have “simple “protocells”, essentially bubbles of fatty acids”, expanding by the addition of further lipids and “pearling” and/or transforming into branched filaments, and to produce more bubbles. No RNA involved in this process though.
And metabolism?
“The one system still missing from these protocells is metabolism. This is particularly challenging because it means creating entire sequences of chemical reactions. In modern organisms, these are controlled by battalions of protein enzymes, which can’t have existed when life began. However, other researchers have begun finding ways to get metabolic chemical reactions going without proteins.”
“startlingly lifelike ‘protocells’”?
Well, we have:
- a lipid vesicle
- RNA whose origin is not discussed
- RNA strand templating with chemistry to prevent degradation of the membrane (speed and fidelity unknown)
What we do not have is:
- a plausible supply of nucleotides, especially through the membrane
- RNA duplication
- a mechanism for vesicle division with RNA division
- metabolism
What we have is essentially an inert bag of Lego bricks, with no information, no energy supply, and highly doubtful material supply. I’ll rephrase the claim of “startlingly lifelike ‘protocells’” as “superficially lifelike to someone who does not grasp the essential nature of living cells.”
It would be easy enough to dismiss all of this as the optimistic musings of a writer aiming to sell a science magazine. But Szostak himself demonstrates the same overreach: “He says there is still some way to go before the system works well enough to sustain living organisms. For example, Szostak wants the copying to be faster and more accurate.”
Similar optimism from Joyce and Szostak eslewhere [4]: “The experiments described above bring the field tantalizingly close to a replicating and evolving protocell.”
Prediction: The Miller–Urey experiment was originally hailed as “life in a test tube” (or tantalizingly close to it), but nearly 70 years later has proven to be little more than tar in test tube; decades from now when the irreducible complexity, intricacy and functionality of the simplest life is properly acknowledged, so will it be for these protocell experiments.
----------
[1] Michael Marshall: “freelance science journalist”; MSc Science Communication, MPhil Experimental Psychology, BA Natural Sciences.
[2] New Scientist, 5 August 2020
https://www.newscientist.com/article/mg24732940-800-a-radical-new-theory-rewrites-the-story-of-how-life-on-earth-began/#ixzz6XS0GHV5a
You can purchase the whole article for USD 1.99 here, as I did: https://www.sciencedirect.com/science/article/abs/pii/S0262407920313774
[3] https://www.newscientist.com/article/dn24669-synthetic-primordial-cell-copies-rna-for-the-first-time/#ixzz6XSHBE3F4
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120706/
“Many ideas have been proposed to explain how it began. Most are based on the assumption that cells are too complex to have formed all at once, so life must have started with just one component that survived and somehow created the others around it. When put into practice in the lab, however, these ideas don’t produce anything particularly lifelike. It is, some researchers are starting to realise, like trying to build a car by making a chassis and hoping wheels and an engine will spontaneously appear.” And, “However, biochemists have spent decades struggling to get RNA to self-assemble or copy itself in the lab, and now concede that it needs a lot of help to do either.”
As an aside, note the invocation of irreducible complexity by a non-ID proponent.
“The alternative – that life emerged fully formed – seems even more unlikely. Yet perhaps astoundingly, two lines of evidence are converging to suggest that this is exactly what happened. It turns out that all the key molecules of life can form from the same simple carbon-based chemistry. What’s more, they easily combine to make startlingly lifelike ‘protocells’.”
The first challenge is finding a plausible natural scenario for the simultaneous production of building blocks for membranes, genetic polymers, and proteins. This possibility is cited:
“By combining a similar organic compound called cyanamide with other simple chemicals, John Sutherland at the MRC Laboratory of Molecular Biology in Cambridge, UK, has created nucleotides, the building blocks of RNA. The reaction requires “ Life’s key molecules can form together thanks to ‘Goldilocks’ chemistry” ultraviolet light, heating and drying, and wetting with water. Sutherland’s team found that the same starting chemicals can also make the precursors of amino acids and lipids. “All the cellular subsystems could have arisen simultaneously through common chemistry,” he concluded. The key is what Sutherland calls “Goldilocks chemistry”: a mixture with enough variety for complex reactions to occur, but not so much that it becomes a jumbled mess.”
The second challenge is their assembly. The author makes this statement: “What’s more, they easily combine to make startlingly lifelike ‘protocells’.”
I’m interested in two aspects of this assertion: “easily combine” and “startlingly lifelike ‘protocells’”.
It is demonstrable that spherical membranes (vesicles) can form spontaneously: “If these lipids were subsequently added to salt water and shaken, they formed spherical blobs with two outer layers of lipids, just like cells.”
Membranes, therefore, can be said to “easily combine”. What about genetic polymers and proteins?
The author has already answered this question with respect to RNA: “However, biochemists have spent decades struggling to get RNA to self-assemble or copy itself in the lab, and now concede that it needs a lot of help to do either.” The appeal to the “everything-first” hypothesis is based on the claim that naked RNA self-assembly and copying doesn’t work. But suddenly we’ve jumped to “easily combining” a lipid membrane around some RNA, self-assembled and even copying itself.
“Szostak’s group has even persuaded RNA to copy itself within protocells.”
Szostak’s work with RNA template copying in protocells requires magnesium ions for nucleotide assembly on the existing RNA, and uses a citrate molecule to clamp on to a magnesium ion preventing it from reacting with a fatty acid but still allowing it to interact with the RNA [3].
It's important to read the fine print: “Despite lacking any of the complex cellular machinery, they can reproduce by dividing to form daughter protocells. “What’s missing is a replicating genetic material,” Szostak says.” So we have “simple “protocells”, essentially bubbles of fatty acids”, expanding by the addition of further lipids and “pearling” and/or transforming into branched filaments, and to produce more bubbles. No RNA involved in this process though.
And metabolism?
“The one system still missing from these protocells is metabolism. This is particularly challenging because it means creating entire sequences of chemical reactions. In modern organisms, these are controlled by battalions of protein enzymes, which can’t have existed when life began. However, other researchers have begun finding ways to get metabolic chemical reactions going without proteins.”
“startlingly lifelike ‘protocells’”?
Well, we have:
- a lipid vesicle
- RNA whose origin is not discussed
- RNA strand templating with chemistry to prevent degradation of the membrane (speed and fidelity unknown)
What we do not have is:
- a plausible supply of nucleotides, especially through the membrane
- RNA duplication
- a mechanism for vesicle division with RNA division
- metabolism
What we have is essentially an inert bag of Lego bricks, with no information, no energy supply, and highly doubtful material supply. I’ll rephrase the claim of “startlingly lifelike ‘protocells’” as “superficially lifelike to someone who does not grasp the essential nature of living cells.”
It would be easy enough to dismiss all of this as the optimistic musings of a writer aiming to sell a science magazine. But Szostak himself demonstrates the same overreach: “He says there is still some way to go before the system works well enough to sustain living organisms. For example, Szostak wants the copying to be faster and more accurate.”
Similar optimism from Joyce and Szostak eslewhere [4]: “The experiments described above bring the field tantalizingly close to a replicating and evolving protocell.”
Prediction: The Miller–Urey experiment was originally hailed as “life in a test tube” (or tantalizingly close to it), but nearly 70 years later has proven to be little more than tar in test tube; decades from now when the irreducible complexity, intricacy and functionality of the simplest life is properly acknowledged, so will it be for these protocell experiments.
----------
[1] Michael Marshall: “freelance science journalist”; MSc Science Communication, MPhil Experimental Psychology, BA Natural Sciences.
[2] New Scientist, 5 August 2020
https://www.newscientist.com/article/mg24732940-800-a-radical-new-theory-rewrites-the-story-of-how-life-on-earth-began/#ixzz6XS0GHV5a
You can purchase the whole article for USD 1.99 here, as I did: https://www.sciencedirect.com/science/article/abs/pii/S0262407920313774
[3] https://www.newscientist.com/article/dn24669-synthetic-primordial-cell-copies-rna-for-the-first-time/#ixzz6XSHBE3F4
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120706/