How Did Life Begin?

May 30, 2018

By Jack Szostak

Is the existence of life on Earth a lucky fluke or an inevitable consequence of the laws of nature? Is it simple for life to emerge on a newly formed planet, or is it the virtually impossible product of a long series of unlikely events? Advances in fields as disparate as astronomy, planetary science and chemistry now hold promise that answers to such profound questions may be around the corner. If life turns out to have emerged multiple times in our galaxy, as scientists are hoping to discover, the path to it cannot be so hard. Moreover, if the route from chemistry to biology proves simple to traverse, the universe could be teeming with life.

The discovery of thousands of exoplanets has sparked a renaissance in origin-of-life studies. In a stunning surprise, almost all the newly discovered solar systems look very different from our own. Does that mean something about our own, very odd, system favors the emergence of life? Detecting signs of life on a planet orbiting a distant star is not going to be easy, but the technology for teasing out subtle “biosignatures” is developing so rapidly that with luck we may see distant life within one or two decades.

To understand how life might begin, we first have to figure out how—and with what ingredients—planets form. A new generation of radio telescopes, notably the Atacama Large Millimeter/submillimeter Array in Chile’s Atacama Desert, has provided beautiful images of protoplanetary disks and maps of their chemical composition. This information is inspiring better models of how planets assemble from the dust and gases of a disk. Within our own solar system, the Rosetta mission has visited a comet, and OSIRIS-REx will visit, and even try to return samples from, an asteroid, which might give us the essential inventory of the materials that came together in our planet.

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20 comments on “How Did Life Begin?

  • @OP link – Researchers are just beginning to identify the sources of chemical energy that could enable the RNA to copy itself, but much remains to be done. If these hurdles can also be overcome, we may be able to build replicating, evolving RNA-based cells in the laboratory—recapitulating a possible route to the origin of life.

    What next? Chemists are already asking whether our kind of life can be generated only through a single plausible pathway or whether multiple routes might lead from simple chemistry to RNA-based life and on to modern biology.
    Others are exploring variations on the chemistry of life, seeking clues as to the possible diversity of life “out there” in the universe.
    If all goes well, we will eventually learn how robust the transition from chemistry to biology is and therefore whether the universe is full of life-forms or—but for us—sterile.

    It really is good to see a nice simple summary for the public, of the present state of scientific understanding of exobiology, coming from someone who really does know his subject in detail!
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  • Erol #2
    May 31, 2018 at 5:30 am

    If anyone wants a more detailed overview of how complex life forms (i.e. Eukaryotes)

    I think it is well established that multicellular organisms evolved from single cells and colonial organisms. Some single celled organisms which reproduce by cell division simply failed to separate, and the cells took on specialist functions as can be seen in colonial organisms and symbiotic relationships.

    The author of this article goes much further back into the origins of life from chemical reactions.

    https://origins.harvard.edu/pages/research-spotlight-jack-szostak

    Making Life from Scratch
    Biochemist Jack Szostak’s Search for the First Cell (2012)

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  • Its nice to see an “official account” of the significance of early geology etc. on the process of abiogenesis. Sorely neglected, but happily in line with my predictions. Two things to add are the UV insolation would be anything up to three orders of magnitude higher than today, giving a very broad spectrum of ionising radiation densities going down through the water allowing a sweet spot to be found between mutation rate and stability. Tides at a hundred times bigger (though the amplifying effects of land constrictions were less) very possibly helped mix the contents of the “reaction vessels”.

    The growing consensus is that abiogenesis is easy. The real challenge is complex life, but even there research is cracking on.
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  • Well y’all can spout yer crackpot heathen (yes you’re all damned) theories about abiogenesis and give it a fancy name but that don’t make it real syense. For one thing there was no syentists there to see it so it’s all specyulashun not real syense. Heck you even got the first book of the bible in yer name for it which means it must have been god that did it. I know that for an akshul fact cos god revealed hi’self to me when I dun preyed to him and the more I prey the more he reveals hi’self to me. Maybes you hell damned syentists should prey more and interfere in god’s domain less. He will judge you and y’all will be found wanting.
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  • Alan,

    I think eukaryote evolution through endosymbiosis is the front runner hypothesis.

    Lynn Margulis (formerly Sagan…. yes his first wife) proposed this and actually it answers most of the problems, not least the striking genetic similarity between the essential energy producing organelles mitochondria and chloroplasts and bacterial cells. The “failed to separate and co-evolve” is hugely less likely having no viable intermediary survival mechanism. Once a power plant organelle is in place it is possible the “lesser” organelles might evolve in situ.

    Here’s a great paper summarising the endosymbiosis approach.

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4571569/

    Unfortunately Margulis went too far, seeking symbiotic mechanisms to comprehensively supplant Neo-Darwinian ideas of species creation.
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  • The discovery of thousands of exoplanets has sparked a renaissance in
    origin-of-life studies. In a stunning surprise, almost all the newly
    discovered solar systems look very different from our own. Does that
    mean something about our own, very odd, system favors the emergence of
    life? Detecting signs of life on a planet orbiting a distant star is
    not going to be easy, but the technology for teasing out subtle
    “biosignatures” is developing so rapidly that with luck we may see
    distant life within one or two decades.

    The striking idea is “biosignature”, which doesn’t rely in immense atmospheric possibilities of the extrasolar planets. It’s extremely common people to wait similar conditions to earth, but unfortunately it seems
    improbable to happen in the same way if there’s no strict laws driving the moment of conception…

    Hopefully these new approaches by radio telescopes may improve our notions about prime environmental stages and then we’ll find the best simulations to achieve next steps in understanding the complex life.

    Now as the gases cool they start to foam,

    And form a dense and fertile cosmic loam;

    An iridescent mist in tempest’s trail.

    Cast out by winds…

    Into your fragile shell this storm is blown,

    Bestowing you with powers once unknown,

    Creating clouds that are no longer frail.

    So as the gaping void starts to exhale

    New life expands like ripples from a stone.

    Cast out by winds…

    Samuel Illingworth
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  • phil rimmer #7
    May 31, 2018 at 7:32 am

    I think eukaryote evolution through endosymbiosis is the front runner hypothesis.

    We know the mechanism is well established in the evolution of mitochondria and chloroplasts.
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  • phil rimmer #7
    May 31, 2018 at 7:32 am

    The “failed to separate and co-evolve” is hugely less likely having no viable intermediary survival mechanism.

    I would not see these mechanisms as mutually exclusive, and would certainly see some intermediate examples.

    Single cells containing assimilated endosymbionts, could still be colonial.

    https://www.quora.com/Why-are-colonial-organisms-not-considered-multicellular

    The boundary between colonial and multicellular is indistinct; nature doesn’t always fit the rigid little conceptual boxes of human vocabulary.

    The difference between colonial and multicellular generally hinges on the degree of functional specialization among the members. If all members of an aggregation can perform all the basic functions of life for themselves, so none of them depends on others to do things they cannot, then the aggregation is a colony. If some members of the aggregation carry out functions that others cannot, so their respective contributory functions are each necessary to the survival of the whole, then it is a multicellular organism.
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  • phil rimmer #7
    May 31, 2018 at 7:32 am

    The “failed to separate and co-evolve” is hugely less likely having no viable intermediary survival mechanism.

    I would see close parallels between stem cells differentiating into specialist organs, and single cell organisms dividing to produce colonial bodies with some still connected cells taking on specialist functions.
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  • Alan #12

    Certainly cyanobacteria (prokaryote) are colonial. But there have not been reports of organisms with appended cells as you describe, so far as I know. Known are symbiotic colonies of two or more cyanobacteria.

    Stem cells certainly figure in fungi, which are self supporting and eukaryotic, and which recently have been pushed back to 1.5bn ya and lichen (an algal prokaryote/fungal non-self supporting eukaryote symbiont) possibly at 2bn ya. I don’t believe eukaryotes arose as early as 3.5bn ya as a few claim, but this timeline ties in best with most other estimates.

    https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life

    The 500 million year hiatus between eukaryotes and multicellular life would be the period of developing versatility in say the Apparatus of Golgi by evolutionary means to create “symbiont-on-demand-cells” or rather stem cells.

    Well that’s my hypothesis…
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  • phil rimmer #14
    Jun 1, 2018 at 1:23 pm

    Alan #12

    Certainly cyanobacteria (prokaryote) are colonial. But there have not been reports of organisms with appended cells as you describe, so far as I know. Known are symbiotic colonies of two or more cyanobacteria.

    The problem with early single cells is the lack of fossilised preserved material.

    There are however indicative examples of relationships in modern more complex species.

    For example in Slime Moulds, two species can merge to form a chimera/colonial body, which is symbiotic in its search or food, but parasitic in the sense that only the dominant species reproduces.

    Sports and chimeras are common in plants.

    In nature, many features do not fit into the little human-devised boxes of linguistic convenience.

    In modern organisms reproducing with horizontal gene exchange and non-sexual cell division, many of the boundaries of “species” are very blurred. They were probably more blurred in the earliest forms.
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  • Alan, I think you are entirely right to voice caution about the manifold and subtle interactions that do happen. Horizontal gene transfer, viruses even and the varieties of co-habitation… Fossil remains of soft bodies remain, if at all, only in residual chemistry and identified inferentially.

    But I still don’t see an argument here for the creation of eukaryotes via a stem cell kind of process. Slime moulds are already eukaryote. Or are you saying eukaryote but not stemcell capable yet?

    In picking lichen I was arguing that differentiated cells that are useually necessary to form variegated structures (so differentiated cells of identical genetic make-up…stem cells differently expressed) are not present though structure was. The interaction of a singular prokaryote and a singular eukaryote created structure. Though the same type of eukaryote (fungus) achieved a structure (allegedly) all on its own through (presumably) learning the stem cell trick of variegated cell expression.

    I must warn onlookers that I am in possession of a dangerously small amount of knowledge in these matters.
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  • phil rimmer #19
    Jun 2, 2018 at 5:55 am

    But I still don’t see an argument here for the creation of eukaryotes via a stem cell kind of process. Slime moulds are already eukaryote. Or are you saying eukaryote but not stemcell capable yet?

    I think stem-cells are a residual form of earlier pre-diversification ancestors, which later evolved specialisms and specialist organs.

    In plants simple mutations can make radical a-sexual transformations such as variegation, or cristate growth forms.

    In both Liverworts – and for that matter insects, there can be different generations with substantially different structures.

    These are modern multicellular species, but they illustrate radical structural and functional differences arising from cell divisions within an individual.

    Given that evolution proceeds in small steps, we need to look for simple origins of both symbionts and capabilities for variation in their earlier separate existence.

    The Slime Moulds illustrate symbiosis between closely related species, but very early life forms likely lacked the genetic stability of modern DNA cells, so replication could easily blurr identity where “gene” exchange was involved.
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