Scientists discover chemistry that may help explain the origins of cellular life
phys.org
phys.org
It's a little like we're trying to reconstruct modern industrial civilization by assuming Dow Chemical exists whenever necessary. Dow and the entire chemical industry arose from a bootstrapping process in which simple feedstocks become ever more complex inputs to ever more specialized industries. The Industrial Revolution would have been impossible without it.
This study looks at the ability of alpha-hydroxy acids to spontaneously assemble semi-permeable compartments ("microdroplets") that could have played an early role, concentrating reactive species and enabling reactions that couldn't take place otherwise. As such, they'd serve as a kind of scaffolding. Useful for a time, and then discarded with the appearance of better structures.
Four out of 5 of these candidates (which are all hydroxy analogs of amino acids), are chiral. The rate of formation, permeability, and durability of the compartments formed might expected to depend on the enantiomeric purity of the starting hydroxy acids.
Surprisingly, the study apparently says nothing about enantioenrichment of the alpha-hydroxy acids. Then again, the study only begins to scratch the surface of what this new chemical system might be capable of.
AFAICT, this is a brand new, highly hackable chemical system with vast potential not just in the origin of life, but across chemistry and biology.
So far, the study only demonstrates inclusion of dyes. The real test will be to get these things to facilitate reactions that would not occur in the surrounding medium.
Given the rarity (AFAIR) of moons as large as ours orbiting planets as small as ours, that might also explain the apparent rarity of life in the cosmos.
Life has had a lot of time to build up mechanisms to protect against UV light [1], including sophisticated dna repair mechanisms and creating sophisticated antioxidants and regulation mechanisms.
But at the dawn of life, whatever self-catalyzing reaction which constituted the first replicators would have been extremely fragile and unlikely to tolerate baking as you suggest.
[1] In David Goodsell's book "The Machinery of Life", p.112, he mentions that when you stand in the midday sun without sunblock, UV light can cause adjacent cytosine and thymine rungs on the dna to cross link to each other. A repair mechanism sweeps the dna looking for this exact bond to unlink it before it gums up normal dna transcription activity. How often does it happen? 50 to 100 times per second ... per exposed cell.
"...simple [chemicals] spontaneously polymerize and self-assemble into [bigger chemicals] when dried at moderate temperatures followed by rehydration."
The first half of the book is about the history of oxygen on the planet and interesting details on how we can know it. The second half of the book is about oxygen processes on life mostly at the cellular level but also some at the whole-organism level.
The book is pretty dense but it is fill with enough interesting ideas, such as why it is believed that cells had developed the ability to produce antioxidants before there was much free atmospheric oxygen. There is a discussion of how can it be that at every cellular division there is a certain fraction of transcription errors, yet the germ line still can pass on for billions of generations and still produce a healthy population.
Statistically speaking... as in mean civilisations per galaxy, yep I agree, no idea where that might land!
In the galaxy overall from what we know now about occurrence of planets in habitable zones, there likely should be tens of million earthlikes with a substantial sized moon.
This article would be comparable to some future generation trying to figure out how our computers were made and then stumbling upon factory that could make the cases. The case is important, but relatively trivial part of the machinery. Similarly, the cell membrane is critical (not just important), but very simple compared the molecular machines (and more) involved in all cells.
Personally, I think if someone researches the physics/chemistry/biology deeply enough, he'll get to the conclusion that abiogenesis not possible naturally with the physical laws we have now. I believe this is an opening for a proof that this world is really a simulation.
Anyone else feel like that?
The "RNA World" hypothesis [0] and the flexibility of RNA as both a self-replicating and catalytic molecule gives us a pretty convincing conceptual pathway to the development of the central dogma of molecular biology we understand today (DNA -> RNA -> Protein) -- especially considering DNA translation mechanisms are nearly entirely powered by ribozymes. Understanding how semipermeable membranes may spontaneously form to "protect" other molecular species like RNA is a pretty foundational step in trying to understand the recipe for the formation of early life.
The simulation hypothesis is fun and all, but I don't think it's a reasonable stand-in for abiogenesis. You're basically invoking God or a Godlike entity at that point, when we have pretty reasonable pathways to conceptualizing the development of early life.
These phrases come up very often when discussing Origin of Life, but it's basically handwaving. It's like saying "we built a plane, which gives us a convincing conceptual pathway on how to get to the moon." The differences in complexities are sooo vast, there is really no comparison.
I can state it more clearly - We couldn't create a functioning cell from scratch (atoms) if we wanted to. I'm not talking about injecting/replacing DNA in an existing cell as Craig Venter et al do (which is impressive. You'll see many articles talk about "we built the first cell" or even add the words "from scratch" but this is what they did.)
I mean build all the functioning pieces - all the molecular machines (https://en.wikipedia.org/wiki/Molecular_machine) and other components. I don't even think we yet understand all the pieces.
You can read some of my questions about abiogenesis at https://biology.stackexchange.com/users/13238/yehosef - some of the questions and answers may highlight the complexity.
You're right, biology is a complex field that, mechanistically, we don't understand all of the intricacies of from first (physical) principles. But invoking the simulation hypothesis as a reasonable substitute for what you, personally, believe is the unlikelihood of abiogenesis is functionally equivalent to suggesting Satan planted dinosaur bones underground to misguide our faith. I don't understand how you think, "could this be evidence of a simulation" is any less hand-wavy than, "RNA has catalytic properties that suggest lifeforms may have begun as RNA-based. In fact, there are viruses that self-replicate by hijacking cellular machinery that are entirely RNA. It's not unreasonable to believe that, given long enough timeframes, similar constructs may have spontaneously self-replicated, even if inefficiently."
The difference between biology and computation is that the mechanics of large-scale molecular systems are, in most cases, too chaotic with too large of a surface area of potential interactions to explain every step as a direct, in vitro replicable chemical reaction - we must approximate where possible. We have to rely on the properties of large stochastic systems, nearly unfathomable timeframes, and extremely rare events to explain most of the world we see around us today.
Yes, every element of the biological world is entirely unlikely. That's kind of the whole reason the field is so beautiful. It only works because there's just so dang much organic material, a constant and consistent heat lamp, and it's all been shaking around violently in a water bath for 3.8 billion years.
We're talking about one amoebae - try to make just one.
Sorry I mentioned the Simulation hypothesis - it's a red herring. It's not important.
>We have to rely on the properties of large stochastic systems, nearly unfathomable timeframes, and extremely rare events to explain most of the world we see around us today.
This is if you want things to happen by chance in a myriad of different environments (acidic, basic, oxidizing...) then we think that a few billion years is enough. But in a lab settings, you can get things just right and coerce the reactions you want. Even then, controlling everything, we have know idea how we could do it. If you know a molecular or evolutionary biologist who disagrees, I'd love to talk with them.
And these time frames are very fathomable - big, but things we can put our head around. We can talk about the physics and dynamics of the universe, the great expansion, etc. It's not something that's beyond us. Making diamonds naturally is a long, multi-million/billion year process. But now we can make them in the lab. With cells, we're talking about a similar time frame but something vastly more complicated.
As I said, when I look at the science/math I don't see any current models of abiogenesis (RNA world, protocells, etc.) as remotely viable. IMO, the only reason for a to hold on to this approach is because the alternatives are untenable. I'm open to hearing other approaches - proving or denying abiogenesis does not threaten my worldview.
BTW - Sir Fred Hoyle (an atheist) used his "tornado in a junkyard" idea (https://en.wikipedia.org/wiki/Junkyard_tornado) to describe what he thought was the likelihood of a working cell forming naturally.
The idea is universally reject by evolutionary biologist, as Wikipedia states, "no biologist imagines that complex structures arise in a single step." The problem that gets swept under the rug is that until you have a single functioning cell, there is no reproduction and therefore nothing that will perpetuate the chemical advances made to get there.
It is unreasonable. I'm afraid your long enough timeframes (3.8 billion years) are not even remotely close to long enough if you consider any serious actual statistical measure of how long it would need for something as complex as just a single cell to "spontaneously" exist, the numbers just don't workout.
Any hypothesis that just guesses how life started with no substantial evidence whatsoever, is just a desperate try to blind yourself form the elephant in the room, that this insane complexity can't just make itself.
No matter how long time passes, a watch can't just come to existence without a watchmaker.
And we have massive issues with simulating single molecule interactions or protein folding. We are nowhere near simulating a single cell without all its external interactions. Not even remotely close.
The field of molecular simulation is holistically based on shortcuts and abstractions to make something out of that research funding. Supercomputers are crunching away at massively simplified models.
And even if we had single cells working a whole new world of complexity opens up next. Interactions with other cells and even worse, the environment where everything from pH over temperature to pressure and light has to be considered.
It's really a condescending bias in disguise. Because I, who consider myself awesome and smart, cannot decipher how this could have come into being, then it clearly must be the work of a deity.
To me, once you have mass scale evolution, such that you have ?quadrillions? of individual organisms doing their own survival calculations and experimentation over billions of years, then the amazing powers of the forms of life don't seem impossible.
It remains to be seen with all the habitable-zone worlds being discovered what is out there.
You're definitely correct that we often apply our mindset onto the world and interpret events according to the model we've made for ourselves. It's hard to be brutally objective and accept the facts, even if it means throwing everything I know out the window. (note, I'm saying this about the meta discussion, not this specific one.)
First of all, the time is not enough, given the complexity of a single cell, the number of conditions/variables needed for something like that to just blindly happen is absurd, a couple billion years is nothing.
Secondly, even if we assume enough time just for the sake of argument, time is not the only factor, you can't just throw "given enough time" and fix everything, things don't just make itself given enough time, a plane would not just come to existence given a billion years.
It's very easy to just oversimplify and throw "billions of years" "mass scale evolution", but once you check the details, it's just not that simple.
Or that we are missing some physical laws. I wonder if it's not kind of all the same ultimately. What difference do you make between a simulation and a physics system knowing that there is logical reasons why my screen lights up the way it does when I'm playing a video game for example. There is a logical explanation on how my avatar has spawned, it's because some code is executed.
What is a simulation exactly? Something where things appears out of.. what? out of nothing logical? Why not I guess.
A matrix/simulation origin allows goofy things like ring species, parasites and molluscs with lots of different eye paradigms - they're either glitches or leftovers from the last run, or exercizes in imagination for the matrix runners.
You either choose the universe itself to be infinite (always have and always will exist) which contradicts all our observations about it, or you assume a higher entity (outside the universe) that is infinite (always have and always will exist).
The third option (nothing infinite) means we wouldn't exist at all, because if there's no "start" then you go into an infinite loop trying to find a start and nothing happens. But since we are actually here, then third option is out, and only the second option (higher entity) makes logical sense.
People don't like to be told what to do, so they'd rather the simulation.
On a "what created the universe" level, they are both identical.
...Rather than invoking a god which comes with its own problems (i.e. who/what created the creator) one could infer that life came from a universe where the physics/conditions for creating life are possible, and life somehow crossed branes moving from one universe to the next.
Consider a reverse/inverted universe where instead of space being a void, space is solid containing voids/cavities/pathways between voids, allowing complex chemical processes to occur naturally and at great scale.