We've been wrong about the origins of life for 90 years

We've been wrong about the origins of life for 90 years
Credit: NOAA Photo Library/Flickr, CC BY-SA

For nearly nine decades, science's favorite explanation for the origin of life has been the "primordial soup". This is the idea that life began from a series of chemical reactions in a warm pond on Earth's surface, triggered by an external energy source such as lightning strike or ultraviolet (UV) light. But recent research adds weight to an alternative idea, that life arose deep in the ocean within warm, rocky structures called hydrothermal vents.

A study published last month in Nature Microbiology suggests the last common ancestor of all living fed on hydrogen gas in a hot iron-rich environment, much like that within the vents. Advocates of the conventional theory have been sceptical that these findings should change our view of the origins of life. But the hydrothermal vent hypothesis, which is often described as exotic and controversial, explains how evolved the ability to obtain , in a way that just wouldn't have been possible in a primordial soup.

Under the conventional theory, life supposedly began when lightning or UV rays caused simple molecules to join together into more complex compounds. This culminated in the creation of information-storing molecules similar to our own DNA, housed within the protective bubbles of . Laboratory experiments confirm that trace amounts of molecular building blocks that make up proteins and information-storing molecules can indeed be created under these conditions. For many, the primordial soup has become the most plausible environment for the origin of first living cells.

But life isn't just about replicating information stored within DNA. All living things have to reproduce in order to survive, but replicating the DNA, assembling new proteins and building cells from scratch require tremendous amounts of energy. At the core of life are the mechanisms of obtaining energy from the environment, storing and continuously channelling it into cells' key .

Where this energy comes from and how it gets there can tell us a whole lot about the universal principles governing life's evolution and origin. Recent studies increasingly suggest that the primordial soup was not the right kind of environment to drive the energetics of the first living cells.

It's classic textbook knowledge that all life on Earth is powered by energy supplied by the sun and captured by plants, or extracted from simple compounds such as hydrogen or methane. Far less known is the fact that all life harnesses this energy in the same and quite peculiar way.

We've been wrong about the origins of life for 90 years
Did life evolve around deep-sea hydrothermal vents? Credit: U.S. National Oceanic and Atmospheric Administration/Wikimedia Commons

This process works a bit like a hydroelectric dam. Instead of directly powering their core metabolic reactions, cells use energy from food to pump protons (positively charged hydrogen atoms) into a reservoir behind a biological membrane. This creates what is known as a "concentration gradient" with a higher concentration of protons on one side of the membrane than other. The protons then flow back through molecular turbines embedded within the membrane, like water flowing through a dam. This generates high-energy compounds that are then used to power the rest of cell's activities.

Life could have evolved to exploit any of the countless energy sources available on Earth, from heat or electrical discharges to naturally radioactive ores. Instead, all life forms are driven by proton concentration differences across cells' membranes. This suggests that the earliest living cells harvested energy in a similar way and that life itself arose in an environment in which proton gradients were the most accessible power source.

Vent hypothesis

Recent studies based on sets of genes that were likely to have been present within the first living cells trace the origin of life back to deep-sea hydrothermal vents. These are porous geological structures produced by chemical reactions between solid rock and water. Alkaline fluids from the Earth's crust flow up the vent towards the more acidic ocean water, creating natural proton concentration differences remarkably similar to those powering all living cells.

The studies suggest that in the earliest stages of life's evolution, chemical reactions in primitive cells were likely driven by these non-biological proton gradients. Cells then later learned how to produce their own gradients and escaped the vents to colonise the rest of the ocean and eventually the planet.

While proponents of the primordial soup theory argue that electrostatic discharges or the Sun's ultraviolet radiation drove life's first , modern life is not powered by any of these volatile energy sources. Instead, at the core of life's energy production are ion gradients across biological membranes. Nothing even remotely similar could have emerged within the warm ponds of primeval broth on Earth's surface. In these environments, chemical compounds and charged particles tend to get evenly diluted instead of forming gradients or non-equilibrium states that are so central to life.

Deep-sea hydrothermal vents represent the only known environment that could have created complex organic molecules with the same kind of energy-harnessing machinery as modern cells. Seeking the origins of life in the made sense when little was known about the universal principles of 's energetics. But as our knowledge expands, it is time to embrace alternative hypotheses that recognise the importance of the energy flux driving the first biochemical reactions. These theories seamlessly bridge the gap between the energetics of living cells and non-living molecules.


Explore further

Kinetic analysis challenges theories of chemistry for the origin of life

More information: Madeline C. Weiss et al. The physiology and habitat of the last universal common ancestor, Nature Microbiology (2016). DOI: 10.1038/nmicrobiol.2016.116
Journal information: Nature Microbiology

This article was originally published on The Conversation. Read the original article.
The Conversation

Citation: We've been wrong about the origins of life for 90 years (2016, August 16) retrieved 17 July 2019 from https://phys.org/news/2016-08-weve-wrong-life-years.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
78 shares

Feedback to editors

User comments

Aug 16, 2016
Any account of the primordial conditions precursory to life must account for the 100% chirality of its amino-acid distribution. This is so extraordinarily stringent a constraint, that only a highly polarized, ultraviolet, light regime to maintain a d-isomer-free primordial environment over a long stretch of time will satisfy the requirement.

Aug 16, 2016
Progressives will restore certainty to science like the Cold War Soviet Empire.

Aug 16, 2016
An admission without admitting it of what I have been saying for a long time.
They cannot create life. They produce dozens and dozens of situations that they claim are similar to the early Earth, and come up with some chemical components claimed to exist in cells, but they do nothing, They just sit there. They talk about energy, but it appears life is more than that. Life is something they won't make in their conventional laboratories, if at all, anywhere. So they change their description about the conditions it purportedly arose under, to buy more time for the claim that life necessarily came from random inanimate matter to continue. And they also change their assertion that life is plentiful in the universe to saying that life may exist only on Earth. They won't admit that God brought life about. Just like they never once saw an actual entirely new species emerge from a different species, but insist that that necessarily must be the way they came about.

Aug 16, 2016
This is so extraordinarily stringent a constraint


That simple chance can explain it. Left and right handed biochemistry are not mutually compatible in reproduction, and both are "eating up" the same chemicals AND each other to make more of themselves, and both are increasing at an exponential rate.

The difference of two exponential rates is itself exponential, so if one got a slight head-start by plain luck, it will quickly take over completely. After one chirality is established, the other can no longer arise.

It might be the case that the very early earth had different chiralities of life in different vents before complex cells arose, but once life went global , one or the other eventually had to take over.

Aug 16, 2016
They won't admit that God brought life about.


Pray tell, what is life?

The quest for the origins of life is at the same time exploration to what life is in the first place, because religious explainations do not shed light on what is meant by the word "life" just as they don't give any meaningful explaination to what is meant by "god".

Saying "God brought about life" is empty and answers no question because you do not know what either of those words actually mean. If you do, please point a finger to this "god" or "life" so that anyone can unambiguously recognize what you mean.


Aug 16, 2016
None of us know how life started, so why don't the superstitious just make up some silly stories? How many have we had so far? How many turned out to be true?

How many religions are true?

None.

Aug 16, 2016

Saying "God brought about life" is empty and answers no question because you do not know what either of those words actually mean. If you do, please point a finger to this "god" or "life" so that anyone can unambiguously recognize what you mean.


This discussion has no place here. You're feeding the trolls.

You're likely aware that science has a pretty good description of what we consider life, as potentially myopic as that description is:
(http://www.nasa.g...on.html)

I'd wager that you're also aware that most if not every religion's deity is described as being outside of a human's ability to observe and/or directly measure, so not only are you feeding the trolls, you're trolling the trolls.

Which means that me responding to you is also... feeding the trolls. Ignore user activated.

Aug 16, 2016
Perhaps we should be seeking similar environments on Mars, in the search for life.

Aug 16, 2016
"They won't admit that God brought life about."

The creation of life by accident, or by thermal self-assembly seems a ridiculous idea, and only a guided self-assembly would seem to be capable of such. Who or what does the guiding though? Neutrinos from the Sun I'd wager, they have an infinite data capacity, and can affect the state of matter by simply passing close to it, and not having to collide with it. So perhaps the God that created life is the Sun, as some ancient societies believed.

A force model of the Universe and the role of Neutrinos.
http://www.beckwi...ODEL.pdf

Aug 16, 2016
@julianpenrod

This comments section on a this physics news site is probably one of the least likely places that you'll be successful in finding someone open to the idea of spiritual beings, or anything that cannot be -empirically- proven to the degree that science demands.

Furthermore, religious discussions are against the forum rules, though the moderators here seem to have given up.

Aug 16, 2016
The anonymous snipers operate here freely, making personal attacks with glee and impunity.

"Moderators"??

HAHAHAHA!

I have asked and asked to them to police this forum, and threatened them with legal action which I am still pursuing. I hope they are not paid.

Aug 16, 2016
Perhaps we should be seeking similar environments on Mars, in the search for life.


Hydrothermal vents on Mars seem unlikely due to its current lack of an ocean (Joke), but life could perhaps exist underground, perhaps around volcanic provinces where it's still warm, shielded from the frozen, low-pressure, acidic radiation-baked nightmare of Mars' surface conditions.

I do like the implications for Europa though. Saltwater ocean, likely in contact with a rocky ocean floor, kept warm by tidal flexing, shielded from the harsh radiation environment of the surface by kilometers of ice... The icy moons of the outer solar system could be teeming with bioluminescent squid monsters and crab people, and we're still thinking we're alone on this rock.

Aug 16, 2016
Azrael, Enceladus is better, since it also has geothermal heat, with evidence from the sampling of its plumes by spacecraft.

Aug 16, 2016
This comments section on a this physics news site is probably one of the least likely places that you'll be successful in finding someone open to the idea of spiritual beings
Julian isnt here to save anybody. Hes here to prove hes surrounded by evil demons.

His personal god is a selfish god.

Its easy to do when you lie to yourself as much as he does. Its how the psychopath george kamburoff can maintain the illusion that he can lie without any of the goobers here finding him out.

Theyre both obviously so much better than everybody else you see, and they enjoy showing this off.

Self delusion is bliss.

Your demons are on the INSIDE.

Aug 16, 2016
I have asked and asked to them to police this forum, and threatened them with legal action which I am still pursuing
"The basic assumption that the truth lies between the testimony of the two sides always shifts the advantage to the lying side and away from the side telling the truth. Under most circumstances, this shift put together with the fact that the truth is going to also be twisted in such a way as to bring detriment to the innocent person, results in the advantage always resting in the hands of liars - psychopaths.

"Even the simple act of giving testimony under oath is useless. If a person is a liar, swearing an oath means nothing to that person. However, swearing an oath acts strongly on a serious, truthful witness. Again, the advantage is placed on the side of the liar. [Robert Canup]"

-George is too stupid to see what a waste of time this is. Hes addicted to the thrill you see.

Aug 16, 2016
It is a fact that they have not succeeded in producing life, using only inanimate matter and random type processes. It is true that no species was ever observed to have arisen. It is true that the "fossils" they claim prove "evolution" are resin molds. Azrael talks about wanting only something that is describable necessarily empirically. But any article about economics involves discussions of finances going into the future, and it has never been proved that tomorrow will come. Even "science" demands that, when the claimed theories fall short, you should permit different ideas. Note that one of the "proofs", even if just tacitly but silently invoked, that life must come about by purely random processes on inanimate substance alone is the unproved acceptance that there must be life throughout the universe, even though it has never been seen. That and the unproved presumption by so many that it must not be the case that God is present.

Aug 16, 2016
Good to see some discussion among astrobiologists, even if
Radzvilavicius is in Lane's group. [ https://theconver...s-291802 ]

@dan: It is not 100 %, but close enough. Metabolism is geared towards producing mainly left chiral amino acids and right chiral sugars.

But as Eikka notes, such a symmetry breaking is easy to see in the right circumstances.

In fact, the current paper is consistent with what we know from the genetic system. The ribosome machinery has a "frozen in" two tier chiral selection of amino acids, which is unnecessary with a chiral metabolism. That implies life started out racemic, but when the genetic code evolved a selective filter became necessary in order to repeatably produce polypeptide strings (proteins).

Aug 16, 2016
@julian: "They cannot create life."

Who are they, and what has that got to do with testing theories - this was a *successful test* if you missed that!? Life emerged in nature, as everything else. And now we know more about how.

Moreover, why try to push falsehoods? More than 200 speciation events have been observed already, as anyone with some google fu can verify ... those events won't go away, but the number will increase. You are the perfect illustration to Dawkins's note:

"It is absolutely safe to say that if you meet somebody who claims not to believe in evolution, that person is ignorant, stupid or insane (or wicked, but I'd rather not consider that)."

But I consider wicked, because no one can be that stupid.

And ironically mirroring your inane conclusion, magic believers like religionists will never admit magic doesn't exist.

Aug 16, 2016
This is so extraordinarily stringent a constraint


That simple chance can explain it. Left and right handed biochemistry are not mutually compatible in reproduction.


Left and right polarizing isomers not only can coexist in the same RNA world, but the addition of opposite members increases the number of potentially superior configurations by a power of 2 for each addition. Chance favors a racemic mixture of the primordial precursors.

If we posit the first self-reproducing chain of RNA to have needed at least 50 amino acids, the probability of them all being l-amino acids is absurdly small.

Artificially modified DNA incorporating d-amino acids has been shown to be biologically viable when re-introduced into bacteria.

The only way to account for the almost bizarre 'preference' for l-isomers is the constant destruction of d-isomers by polarized UV radiation. This is not unusual a regime in early stars and their (early) evolving planetary systems.

Aug 17, 2016
@dan: A chemically produced RNA World would be racemic yes. But Joyce showed recently that cross chiral replicators are more efficient, i.e. shorter replicases and more robust product.

Then you claim that DNA incorporates DNA. In modern genetic systems yes, a lot of structural support, but we are talking about a RNA world. It had d-nucleotides, so I don't get your last paragraph. Are you assuming the genetic code had to evolve on the surface?

Let me instead note that vent theory is consistent with a racemic start. An initial vent PCR replication in pores work in racemic mixtures, and can easily produce the evolved ~ 50 mer cross replicases that would support cell pore replication.

So RNA/RNA cells, who would start to use amino acid cofactors and eventually produce unordered polypeptides by the rRNA ancestor. (Could have evolved to be used for catalytic nests.)

Tentative ribosome phylogeny show that it eventually produced ordered polypeptides from mRNA genes.

[tbctd]

Aug 17, 2016
[ctd]

So now we have RNA/protein cells. As I noted previously, the phylogenetic evidence shows that it was the genetic machinery, not the environment, that evolved the preference for d-nucleotides and l-amino acids concurrently.

And to wit, the discussed work argues that the RNA/protein cells evolved in the vents all the way from either the RNA/RNA cells or RNA/protein cells (methyl radicals in the ribosome core), presumably to DNA/protein cells of a LUCA.

I don't understand how surface UV light would be involved at all, and if it was how it selected for d-nucleotides and l-amino acids, concurrently or even sequentially if that would be possible.

Are we even sure UV light reached the surface? Lots of unknowns in the Hadean climate. Maybe at the DNA stage, since it is UV resistant. That would mean a DNA LUCA takeover, which is possible but not attractive.

Then again UV resistance could be a simple byproduct of evolved thermal-chemical resistance.

Aug 17, 2016
In case I was unclear:

- When I say a DNA LUCA may have evolved at the surface (but why - it wasn't photosynthetic) I have to assume there were many RNA common ancestors to choose from, since they had already evolved a code. I.e. some could have used l-sugars, some d- sugars.

Now vents have to be a lot more productive than just evolving a first lineage quickly...

- Here is my specific problem with a solar radiation symmetry breaking as a generic mechanism:

Coded amino acids are levorotatory, while the coding mechanism is dextrorotatory in its building blocks. (Strands and double strands rotation is conformation dependent, c.f. double strand rotation in DNA.) [ https://en.wikipe...emistry) ]

So you can suggest nucleotides were the solar symmetry broken ones. But then you can't explain the other symmetry breaking. What is left unsolved is "how it selected for d-nucleotides and l-amino acids, concurrently [or even sequentially]".

Hi Azrael,

Mars itself is indeed the right bet for discovering the first life forms, albeit microorganisms, away from Earth. The next visit should focus on the volcanic areas. And please remember what you read here: sulfur bacteria are going to be found there.

Aug 21, 2016
It's not like the Alkaline vent theory is that new. The headline is misleading.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more