Tubeworms live around deep-sea vents
economist.com
economist.com
All laid out in Paul Davies' book - fascinating read: https://www.simonandschuster.com/books/The-Fifth-Miracle/Pau...
The reason is that photosynthesis requires very complex structures for which there exists no plausible way to appear in non-living conditions, but only after a long biological evolution from simpler structures.
Photosynthesis is much more correctly named as "phototrophy" (i.e. feeding with light), because light is not used directly in any synthesis, it only provides energy and in some variants, not in all, it also provides reduced molecules that can be used later in redox reactions (typically the so-called NADPH). The name "photosynthesis" was coined at a time when nobody had any idea about how it worked.
The so-called oxygenic phototrophy a.k.a. oxygenic photosynthesis, where free dioxygen is generated by splitting water, has appeared only once, in the ancestor of blue-green algae a.k.a. cyanobacteria, billions of years after the origin of life and a very long time after the bacteria had evolved into a large number of distinct groups.
The anoxygenic phototrophy a.k.a. anoxygenic photosynthesis, where no oxygen is generated, is still encountered in many groups of bacteria, which instead of water oxidize dihydrogen or carbon monoxide or reduced compounds of sulfur or of iron.
It is possible, but far from certain, that anoxygenic phototrophy already existed in the ancestor of all present bacteria. Even in the not very likely case when this were true, there is no doubt that anoxygenic phototrophy has appeared after a long evolution, like also the current genetic code of the nucleic acids, which is also the result of a long evolution from simpler genetic codes, despite the fact that there are no known survivors from that early time.
The results of the current research leave no doubt that the mechanism that has been used by the earliest forms of life for obtaining energy is the one that is still used in the so-called acetogenic bacteria and acetogenic archaea (a.k.a. homoacetogenic bacteria and archaea). For obtaining energy, these convert dihydrogen and carbon dioxide (or carbon monoxide and water) into acetic acid.
So at the origin of life, the required energy source was free elemental hydrogen a.k.a. dihydrogen (or/and carbon monoxide).
Dihydrogen is also produced today in volcanic gases and in hydrothermal vents and it was produced in greater quantities in the past, when Earth had more hydrogen than today, because a significant part of the hydrogen has been lost in space, as it cannot be retained by the gravity of Earth when it is not combined with heavier elements.
Both in volcanic gases and in hydrothermal vents the origin of dihydrogen is in the reaction of volcanic rocks with water, where the water oxidizes the reduced iron ions (FeII) that come from the interior of the Earth into rust (FeIII).
Because volcanic gases are mainly released during violent eruptions, the more peaceful hydrothermal vents, where gases with high dihydrogen content are released slowly during long times in stable conditions are a more likely place for the origin of life.
Moreover, the hydrothermal vents also release alkaline ions (because of the increase in positive electric charge of the oxidized iron ions, which repels the alkaline ions), which create a gradient of ions in their path towards sea water, which is likely to have been an auxiliary source of energy also since the origin of life. All the present life forms still use ion gradients as intermediates in the energy-transforming processes.
The source of energy is the most important factor for the origin of life. There have been plenty of fantastic theories about the origin of life, which have omitted to provide an explanation for a continuous source of energy, without which no form of life is possible, so there is no doubt that all those theories were wrong.
Free dihydrogen is not produced only at the surface of the crust, like in hydrothermal vents, but it is also produced at great depths, wherever volcanic rocks are infiltrated with water. The acetogenic bacteria and the methanogenic or acetogenic archaea do not need any other source of energy, so they can live there without problems.
While the acetogenic bacteria and the methanogenic or acetogenic archaea need only dihydrogen, besides normal constituents of the rocks, like water and carbon dioxide, so they can live at any depth below the surface of the Earth where the temperature is not too great for life, many of the so-called anaerobic bacteria actually need substances, like sulfate or nitrate or oxidized iron, that are products of oxidation caused by the activity of the phototrophic algae and plants, so even when those anaerobic bacteria live in caves or on the deep sea bottom they are still dependent on Sun's light and on the oxygenic phototrophic organisms. Therefore such anaerobic bacteria are unlikely to live at great depths and their metabolism is not relevant for the origin of life.
Probably better investigated by robots than by Musk building a Butlins there.
It does not explain which is the source of energy. Without a continuous source of energy life cannot exist.
Moreover, it does not explain how the soup becomes concentrated enough to enable the formation of complex structures. Any primordial soup would have been too dilute for the dissolved substances to have chances to interact.
The only plausible hypotheses for the origin of life are not in the middle of a soup, but at the surface of some minerals, more likely inside pores in the minerals. The minerals must have been metallic sulfides, more precisely sulfides of iron with some content of cobalt and nickel, as these 3 metals included in sulfide clusters are the catalysts for all the chemical reactions that are necessary and sufficient for sustaining the simplest forms of life.
The catalysts Fe, Co and Ni are equally important with the structural non-metals H, C, N, O and S for the origin of life. Life is impossible without both kinds of chemical elements.
About a half of the amino-acids that are contained in modern proteins can form in the absence of life, and it was supposed that the "soup" contained those ten amino-acids.
The original "soup" theory did not explain how you could get proteins from amino-acids. Proteins cannot form within a soup, because they can form only by extracting water from amino-acids, which cannot happen when they are inside water. (The living cells extract the water from substances like amino-acids, in order to make polymers by condensation, by using special dehydrating agents that are acid anhydrides; the most important classes of such acid anhydrides are either polyphosphoric acids like ATP or thioesters; such dehydrating agents cannot appear naturally in a "soup".)
A way to form proteins would be not in a soup, but on some rock where the water evaporates and leaves a residue of amino-acids that could condense into proteins, more precisely into peptides, in the absence of water. However not even this is good enough to explain the appearance of a self-reproducing system. Such a system can appear only in a place where amino-acids are synthesized continuously (like attached on the surface of minerals with catalytic properties), and not like in the theory of primordial soup where it was supposed that they could be synthesized in the atmosphere, by lightning and UV light, then they would fall in the sea, which could have never concentrated them sufficiently in a single place.
Also the mineral ions that could have existed in a primordial "soup" are not those that could have provided catalytic functions. In the beginning, the primordial ocean contained mostly potassium ions, and later also magnesium ions, because these are the most easily leeched from rocks. The primordial ocean had condensed from volcanic gases and initially it contained only volatile acids, like hydrogen chloride and carbonic acid. Then slowly it has dissolved the more soluble parts of the rocks, so that the dissolved ions, starting with potassium, have neutralized the acids, and then other less soluble ions have been leeched from rocks, until eventually the ocean water has reached the current composition of its salts, but this happened after a very long time, most likely long after the appearance of life.
It would be very unlikely for life to appear in an ocean with the current salt composition, because many of the ions present now in sea water would interfere with the biological chemical reactions. All the living cells that are inside sea water spend a considerable part of their energy with preventing undesirable ions, like sodium and calcium, from entering the cells. At the origin of life, such highly-efficient ion pumps could not have existed, so such harmful ions must have been not abundant in the ocean of that time. Therefore the probability for the appearance of life is much higher on a young planet with a young ocean and the probability decreases on an old planet, where chemical equilibrium is reached.
The primordial ocean acquired relatively soon a high concentration of Fe(II) ions, but those are not suitable as catalysts in the form of hydrated ions. All the ancient enzymes that use iron as catalyst use it in the form of iron-sulfur clusters, exactly like the iron that can be found in non-soluble iron sulfide minerals, so it can be presumed that the original catalysts were iron sulfide crystals alone, without the protein part that is now attached to the iron-sulfur cluster, in order to position it correctly inside the living cells.
>The fifth miracle of Davies' title refers to Genesis 1:11: "Let the Land Produce Vegetation." (The first four Biblical miracles are the creation of the universe, the creation of light, the creation of the firmament and the creation of dry land.) It is proverbial in the popular science publishing world that God is good for sales, especially since Steven Hawking sold millions of copies of an otherwise unremarkable book by promising that a unified physical theory would enable us "to know the mind of God." Commercial requirements alone seem to have dictated that word "miracle," since Davies begins the book by disavowing it. Like other evolutionary scientists he starts with the presumption that "it is the job of science to solve mysteries without recourse to divine intervention." Life is not a miracle because scientists wish it to be a product of natural forces which they can explain.
Just spitballing, haven’t read the book
I also take exception with the concept of "more" or "less" evolved. Do you mean "complexity"?
https://www.nature.com/articles/s41467-024-52631-9
Lots of cool pictures if you like oceanography stuff.
https://www.nature.com/articles/s41467-024-52631-9/figures/2
https://www.nature.com/articles/s41467-024-52631-9/figures/3
I won't pretend to be a biologist, so forgive me if this is naïve, but this does feel like it's at least within the realm of possibility of working similarly on Europa, right? As in a non-zero chance at least.
Or maybe not. Europa’s ocean could be teeming with life.
The Economist magazine is not what it used to be, sadly.
You have severely misunderstood the article.
It is not saying that there are tubeworms (and other animals) around deep sea vents. This, as you say, is well known.
It is saying that they also live underneath the sea bed in cracks in the rocks of the crust. This environment is even more extreme and brutal than in the open oceanic water. It is hotter, much lower in oxygen, and the chemical concentrations are even higher.
The organisms living within the rocks are even more extremophile than the ones in the oceanic water.
The greater point you are missing is that there is a whole other type of ecosystem that is less well known (and I think more recently discovered) than even vent colonies. The environment of organisms living in cracks and crevices of the rocks of the crust, far beneath the surface of the planet.
We've only drilled to ~12km down. The crust is up to 70km thick, comparable to the thickness of the atmosphere.
https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole
The point here is that much of that very large volume is inhabited, by organisms that have been down there for a very long time. Not just millions but billions of years.
Billions-of-year-old rocks contain living organisms:
https://www.discoverwildlife.com/environment/living-microbes...
This is a vast and almost unknown ecological niche, the deep biosphere:
https://en.wikipedia.org/wiki/Deep_biosphere
And now, as the very top part of it at the bottom of the ocean is explored, it has metazoans in it too. Multicellular life, animals, as well as protozoan.
“Under the seabed” would have been more accurate.
Probably didn't want to settle for less but you take what you can get . . .
It’s a shame there weren’t any deep sea potatoes to complete the classic mosselen-friet / moules frites / mussel French fries combo.
Sounds similar to Assembly Theory as promulgated by Cronin et al
(Stumbled upon the answer while formulating the question – no, being capable of doing anti-entropy self-maintenance work isn't AGI-complete because there's plenty of life that's perfectly capable of that without being generally intelligent.)
Compelling argument. However from the moment I understood the weakness of my flesh, it disgusted me. I craved the strength and certainty of steel. I aspired to the purity of the Blessed Machine. Your kind cling to your flesh, as though it will not decay and fail you. One day the crude biomass you call a temple will wither, and you will beg my kind to save you. But I am already saved, for the Machine is immortal.
Jokes aside life may be more robust but in a very narrow set of conditions where it evolved. Look at Mars for example. No life (as far as we know) but three robots happily wandering like what do you mean this planet isn't habitable? Atmosphere? Biomass? Planetary magnetic field? Tell me more
I don't want to be human! I want to see gamma rays! I want to hear X-rays! And I want to - I want to smell dark matter! Do you see the absurdity of what I am? I can't even express these things properly because I have to - I have to conceptualize complex ideas in this stupid limiting spoken language! But I know I want to reach out with something other than these prehensile paws! And feel the wind of a supernova flowing over me! I'm a machine!