Meet Luca, the Ancestor of All Living Things

Jul 25, 2016

By Nicholas Wade

A surprisingly specific genetic portrait of the ancestor of all living things has been generated by scientists who say that the likeness sheds considerable light on the mystery of how life first emerged on Earth.

This venerable ancestor was a single-cell, bacterium-like organism. But it has a grand name, or at least an acronym. It is known as Luca, the Last Universal Common Ancestor, and is estimated to have lived some four billion years ago, when Earth was a mere 560 million years old.

The new finding sharpens the debate between those who believe life began in some extreme environment, such as in deep sea vents or the flanks of volcanoes, and others who favor more normal settings, such as the “warm little pond” proposed by Darwin.


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8 comments on “Meet Luca, the Ancestor of All Living Things

  • Whilst Dr Sutherland may be pissed off with these results, Dr Nick Lane should be jubilant I suspect as this outcome neatly takes the tracks of life across the mud to “his” deep sea vents.



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  • 2
    Pinball1970 says:

    “Dr. Martin’s portrait of Luca “is all very interesting, but it has nothing to do with the actual origin of life,” Dr. Sutherland said.”

    Probably the most interesting question in biology there is?

    Life Ascending & The vital question were such a good arguments for deep sea vents (and other things) it is difficult to find flaws in Nick Lane’s arguments without being an expert in the field.

    They bring out the books we go and read them is all we can do.



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  • @OP – link – Dr. Sutherland and others have no quarrel with Luca’s being traced back to deep sea vents. But that does not mean life originated there, they say.

    It should be no surprise that prior to the evolution of photosynthesis, organisms depended on chemosynthesis! LUCA is the Latest Common Ancesctor, from which all surviving modern life is descended. That should not be confused with earlier now extinct life forms from RNA World, nor should it be conflated with abiogenesis and the intitial origins of life chemistry.

    Life could have originated anywhere and later been confined to a deep sea environment because of some catastrophic event like the Late Heavy Bombardment, which occurred 4 billion to 3.8 billion years ago.

    Early Earth was indeed a place hostile to life in the Hadean Period, so protected sea-floor niches as the seas with their massive tides formed, would seem likely to be the the key to survival of any life.
    They should also provide a diversity of conditions where a wide range of evolutionary opportunities are available – as indeed the hydrothermal vents with their isolated little evolutionary islands of life, still do today.



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  • Sutherland’s work is entirely about pre-biotic chemistry. Lane’s arguments are that deep sea vents are the ideal substrate for bringing together pre-biotic elements for actual biogenesis, so

    Dr. Sutherland and others have no quarrel with Luca’s being traced back to deep sea vents. But that does not mean life originated there, they say.

    over inflates by implication their own achievements. Indeed

    Sutherland cautions that the reactions that would have made each of the sets of building blocks are different enough from one another—requiring different metal catalysts, for example—that they likely would not have all occurred in the same location. Rather, he says, slight variations in chemistry and energy could have favored the creation of one set of building blocks over another, such as amino acids or lipids, in different places. “Rainwater would then wash these compounds into a common pool,” says Dave Deamer, an origin-of-life researcher at the University of California, Santa Cruz, who wasn’t affiliated with the research.

    We can imagine such pools and solutions trapped in pores carried down in a volcanically rent and collapsing surface. Mid ocean type vents may well have been duplicated in far greater numbers and in much shallower seas or again the moving mantle hernias creating island chains like Hawaii may seed vents near island runoffs.

    Geology could be the discipline most likely to help now.



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  • phil rimmer #4
    Jul 26, 2016 at 10:19 am

    Mid ocean type vents may well have been duplicated in far greater numbers and in much shallower seas or again the moving mantle hernias creating island chains like Hawaii may seed vents near island runoffs.

    http://tos.org/oceanography/assets/docs/20-1_tivey.pdf

    The map on the second page of the link (labelled p51) shows large numbers of vents along present-day mid-ocean ridges.

    Geology could be the discipline most likely to help now.

    On page 4 of the link (labelled p53) There is a graph showing temperature and pressure according to depth.

    P5 / p54, shows some of the chemistry.

    Although there are signs of deep-water deposits in the Archean, (4,000 to 2,500 million years ago), the Proterozoic (2,500 to 541 million years ago) features many strata that were laid down in extensive shallow epicontinental seas.
    These seas were at times shallow on the early Earth before the continents formed and surfaced, so there would be implications for pressures and pressure-related temperatures relating to the available depths of ocean water.

    Of course the reducing atmosphere and gases dissolved in the water, would also be substantially different to those of the present day up until the great oxygenation event.



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  • The paper really gives the vent theory a lot more credit than the article accounts for, since it shows that the UCA lineage inhabited alkaline hydrothermal vents since metabolism and genetics geologically evolved. (As seen by methyl radicals in both, as well as FeS catalysts/enzymes in the latter.)

    One can also note that it firmly rejects transpermia, since Valley’s latest zircon review shows that Earth had a habitable ocean > 4.3 Ga, which fits with the Bacteria/Archaea split data of > 4.2 Ga, and the first fossil candidates > 4.1 Ga implying photosynthetic bacteria excluding archaea. [ http://www.minsocam.org/msa/ammin/toc/2015/open_access/AM100P1355.pdf ; http://www.timetree.org/search/pairwise/2/2157 ; http://www.pnas.org/content/112/47/14518.full.pdf ] Meanwhile Mars may have first become habitable as per Curiosity < 4.1 Ga when the Tharsis bulge volcanoes let go.

    @Phil: It is Michael Russell’s vent theory, in fact, discovered the year before alkaline hydrothermal vents were! [For a timeline of his work, see the review in Russell et al “The Drive for Life on Wet and Icy Worlds”, Astrobiology, 2014; http://online.liebertpub.com/doi/pdfplus/10.1089/ast.2013.1110 .]

    For what it is worth, Lane predicts that the LUCA ancestor could only evolved chemiosmosis on the surface of alkaline hydrothermal vents in Sojo et al, which is arguably confirmed by Martin et al modulo the sparse genetic coverage of their method. [ http://nick-lane.net/Sojo%20et%20al%20PLOS%20Biology.pdf ]

    And yes, Sutherland reacts emotionally and/or isn’t up to date with vent theory: “… chemists like Dr. Sutherland say they are uneasy about getting prebiotic chemistry to work in an ocean, which powerfully dilutes chemical components…”. Russell et al has shown how vent pores concentrate organics with a factor 1000, sequential pores multiplying the effect.

    Re soup theory “many pot” pool systems that are arranged “just so”, they are of course much more unlikely than having a competent alkaline thermophoresis reactor. The latter can do everything from fixating C from vent H2 and ocean CO2 to thermo-cycle PCR of RNA from nucleotides, merely from the pH tipping the balance from oxidation to reduction of elemental C. There is a gap between pentose (which may have been produced towards the ocean starting from vent catalyzed pyruvate, see Keller et al metabolic like pathways) to nucleotides, but the pathway is much the same as to pentose given Martin’s now more or less established environmental production of amino acids. It seems unlikely to be a road block, so many has fallen the few last years. (Such as the “tar” and “side reaction” problems, Keller et al pathways reject them; cross chiral RNA replication, is actually easier by a result of Joyce; et cetera.)



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