Complex life evolved out of the chance coupling of small molecules

September 19, 2017
A simple RNA molecule such as this may have been responsible for the evolution of complex life as we know it. Credit: Wits University

Complex life, as we know it, started completely by chance, with small strands of molecules linking up, which eventually would have given them the ability to replicate themselves.

In this world, billions of years ago, nothing existed that we would recognise today as living. The world contained only lifeless that formed spontaneously through the natural chemical and physical processes on Earth.

However, the moment that small molecules connected and formed larger molecules with the ability to replicate themselves, started to evolve.

"Life was a chance event, there is no doubt about that," says Dr Pierre Durand from the Evolution of Complexity Laboratory in the Evolutionary Studies Institute at Wits University, who led a project to find out how exactly these molecules linked up with each other. Their results are published today in the journal Royal Society Open Science, in a paper entitled "Molecular trade-offs in RNA ligases affected the modular emergence of complex ribozymes at the origin of life".

Very simple ribonucleic acid (RNA) molecules (compounds similar to Deoxyribonucleic acid(DNA)) can join other RNA molecules to themselves though a chemical reaction called ligation. The random joining together of different pieces or RNA could give rise to a group of molecules able to produce copies of themselves and so kick start the process of life. 

While the process that eventually led to the evolution of life took place over a long period of time, and involved a number of steps, Wits PhD student Nisha Dhar and Durand have uncovered how one of these crucial steps may have occurred.

They have demonstrated how small non-living molecules may have given rise to larger molecules that were capable of reproducing themselves. This path to self-replicating molecules was a key event for life to take hold. 

"Something needed to happen for these small molecules to interact and form longer, more and that happened completely by chance," says Durand.

These smaller RNA molecules possessed enzyme activity that allowed ligation, which, in turn allowed them to link up with other small molecules thereby forming larger molecules.

"The small molecules are very promiscuous and can join other pieces to themselves. What was interesting was that these smaller molecules were smaller than we had originally thought," says Durand.

The smallest molecule that exhibited self-ligation activity was a 40-nucleotide RNA. It also demonstrated the greatest functional flexibility as it was more general in the kinds of substrates it ligated to itself although its catalytic efficiency was the lowest.

"Something needed to happen for molecules to reproduce, and thereby starting life as we know it. That something turned out to be the simple ligation of a set of , billions of years ago," says Durand.

Explore further: Could interstellar ice provide the answer to birth of DNA?

More information: Molecular trade-offs in RNA ligases affected the modular emergence of complex ribozymes at the origin of life, Royal Society Open Science, rsos.royalsocietypublishing.or … /10.1098/rsos.170376

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szore88
1.7 / 5 (6) Sep 19, 2017
Riiiggghhhtttt.... Chance. The fabric of reality itself was all...chance.... Brilliant. (Rolling eyes...)
somefingguy
1.8 / 5 (5) Sep 19, 2017
That's a bold claim to state that it was 100% pure chance, especially as they were able to replicate this in a lab; that replicating not being a chance event.

I'm not implying God, but to claim that it was chance is fairly presumptuous.
adave
1 / 5 (3) Sep 19, 2017
The next study would be to suggest the chance of self replication. Then the next precursor of complex life from the rna or from pure chance. So what are the numbers? You might describe the chaos as starting at the end branches of a tree diagram and working backwards to the trunk. Pure chance is working with chaos. The diagram says that you have a high probability of chance flowing to the tips not the trunk. Life has to "eat" and die so that the parts are available as an equilibrium. It is good to find the mechanics of the process. Why though has there not been life in all of its precursors discovered somewhere on or under the earth? Life should form continuously unless it required the entropy of the distant past. But that means billions of light years away. How thick is life on the earth? It is limited by solar and geothermal energy. vol life/vol earth shows how hard it is to find something alive. If it were easy we would be living on cheese!
syndicate_51
not rated yet Sep 20, 2017
Keep working guys as it stands by the numbers these odds are highly arguable.

The work isn't done yet.
Steelwolf
5 / 5 (5) Sep 20, 2017
Adave, so far everywhere we go, here on Earth, we keep on finding life, even in gas and oil welld, even in the 2-3 mile deep gold and platinum mines in Africa, on the Atacama Plains, the driest place on Earth, in the Himalayas, with high radiation, low humidity and low oxygen levels, and down in the deepest and coldest of our seas, and algaes living on the ices.

We find life everywhere we look, and as long as you are not in a concrete and asphalt world, then you may as well BE living on cheese, several feet thick.

Since we find life so ubiquitous here, many of us expect to be able to find life as a rule rather than the exception thruought the Universe. Assuredly there will be galaxies sterilized, or nearly so, by quasar activity, or low metalicity so that it never arises. However, from what we can see, where there is water or other ionic-flow supporting fluid and a chemistry and temperature gradient that is not inconducively radical, then life should occur on it's own in time.
sirdumpalot
1 / 5 (3) Sep 20, 2017
It was not chance, but the dependent arising of the necessary conditions for replication to emerge as functionality, property, future condition. Complexity requires time and scale yes, but if chance is taken as the causal nexus of experience, the nexus remains unexplained, but is replaced by an absurdist core ontology.

Experience is not 'this' or 'that', it's not 'look, hey, presto, cause-and-effect, there was 'no Life' now there is 'Life', what does it all mean that it is most important above all but still entirely impermanent?!'. Experience is, at every level, entirely observer dependent. Rather than things or Self, experience is the interrelation between a sequence of interractions that is perceived as the world - relativity, the Copernican principle in full.
Parsec
5 / 5 (5) Sep 20, 2017
We only really have 2 basic options. Either some sort of primitive life started from simple chemicals over a long period of time, or a all powerful all knowing intelligent being emerged simultaneously from the cosmos that had the power to do all we see. If it is the second case, it is still worth studying how the big guy did it.

I believe Occam's razor strongly suggests the 1st explanation for the simple reason that the second one adds an extra layer of complexity without explaining anything extra.
NoStrings
5 / 5 (1) Sep 20, 2017
Parsec, I am with you on the 1st explanation.

However, maybe it is time to do some PhD s in theoretical physics on godology. Why not? We were wa.king on string theory for 45 years. How about a string theory of godology? I am not sure about 'Big Guy' theory though. It is more like a 9 or 10 dimensional spaghetti monster... Still worth researching, and would be a good source of PhD s in phy?whatever, while we are stuck. Mathematics can be such fun.

And a theory of everything, as soon as we explain creation of god.
TheGhostofOtto1923
5 / 5 (1) Sep 20, 2017
Godders want the origin of life to be as predetermined as their ability to escape death. If the major things all happen by chance then what good is praying for special favors? How are they ever going to win the lottery on their own?

God is only a control freak by projection.
TheGhostofOtto1923
not rated yet Sep 20, 2017
Since we find life so ubiquitous here, many of us expect to be able to find life as a rule rather than the exception thruought the Universe
The power of evolution has nothing to do with origin. Ubiquity doesnt mean that it didnt start in only one place, and that that event was exceedingly rare.
Elmo_McGillicutty
2.3 / 5 (3) Sep 20, 2017
A random event is impossible and has never occurred in this universe.

julianpenrod
1 / 5 (2) Sep 20, 2017
Wholly irresponsible claims.
Yes, there are cases where small "organic" related molecules or fragments of larger chains form spontaneously, but that's all they do. There is an enormous distance between even a thousand atom chain segment of DNHA and a cell and that difference is critical. Because, among other things, the cell protects the DNA. Unprotected DNA, or any "organic" related molecule, degrades and breaks apart swiftly! There can be many cases where segments of "organic" related molecules came together, but, unless an entire working cell sprang suddenly into being, they all broke apart quickly and did not lead to anything more complex.
TheGhostofOtto1923
5 / 5 (1) Sep 20, 2017
Wholly irresponsible claims
How would you know?
Yes, there are cases where small "organic" related molecules or fragments of larger chains form spontaneously, but that's all they do
How would you know?
There is an enormous distance between even a thousand atom chain segment of DNHA and a cell
How would you know? Real scientists dont yet know if these things are true or not. What makes you think your guessing is better than their continuing to look?
unless an entire working cell sprang suddenly into being, they all broke apart quickly and did not lead to anything more complex
Once again, how would you know? Perhaps you could imagine how there might be a situation where these processes could occur within a protecting shell of some sort.

No?

Because thats obviously what happened to take place.
Eikka
5 / 5 (2) Sep 20, 2017
but, unless an entire working cell sprang suddenly into being, they all broke apart quickly and did not lead to anything more complex.


You're making the argument of irreducible complexity, which is an illusion. "Unprotected" DNA and RNA do not break down in all conditions - just in conditions that are hostile for them. Now you can ask yourself, could there be any DNA/RNA in such places in the first place?

Obviously, if RNA and DNA came to be through some ambient chemical reaction, it would happen in places that are not hostile to such molecules. The cell as a protective structure came to be when they moved out of that environment, and as the environment no longer exists, it seems that DNA cannot persist without cells - irreducible complexity is merely an argument out of ignorance.

MOKHTAR
1 / 5 (1) Sep 20, 2017
"Life was a chance event, there is no doubt about that,"did this "evolution" a scientific theory or an "ideology" or it take the two senses.
Robert_D
1 / 5 (2) Sep 21, 2017
Life was probably cooked up in a simulation by some adolescent nerd god who got a quantum computer for his birthday. Let's just hope he doesn't strike up a relationship with a god of the opposite sex, lose interest in his experiment, turn off the computer and destroy our universe.

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