Cell biology Evolution Intelligent Design Origin Of Life Tree of life

Molecular biologist: Speculation re the last universal common ancestor is not helping science

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a 2005 tree of life that includes horizontal gene transfer (HGT)/Andrew Z. Colvin, Barth F. Smets, with permission

From molecular biologist Mike Klymkowsky at The Scientist

There is a pernicious temptation in science to speak authoritatively about topics that are beyond scientific exploration and certainty. This has led some theoretical physicists to advocate for a “post-empirical” form of science. That is the idea that theories need not be judged on their ability to make new and testable predictions about the observable universe, in some cases, the absence of a plausible alternative is sufficient.

Klymkowsky is certain that there was a single Last Universal Common Ancestor (LUCA)* but before that?

But what came before and the exact steps leading to LUCA are unknowable. Moreover, the billions of years that have elapsed since LUCA’s origin and the active nature of evolutionary processes that result in new genes “popping out” of the noise and becoming essential in organisms from fruit flies to humans, combined with the reality of structural or functional convergences, the growing recognition of small and alternative open reading frames that encode functionally different proteins, and the ubiquity of various forms of horizontal gene transfer, means that historic details and their evolutionary drivers are often obscure.

Forterre has made a number of points related to what we can know about LUCA. For example, while students are often presented with an implicit model of early life as essentially bacterial or archaeal (prokaryotic), this “just-so” story ignores the fact that these are highly evolved organisms, specialized for specific ecological niches with streamlined genomes. LUCA may well have been more complex than previously thought, but that tells us little about the steps leading to LUCA. More.

Klymkowsky suggests holding off on the just-so stories for students until and unless we know more, to protect the reputation of science. That’‘s wise in pinciple. But the purpose of just-so stories may be to instill in students the notion that science has the answer to questions that used to be referred to philosophy or religion (Stephen Hawking, among others, thought that was true). If so, the main thing is to have an answer or better still, a flurry of answers that keep the mill rolling. And, as long as it is funded, who’s going to complain?

It may never be possible to discover the last universal common ancestor for the same reasons as it may never be possible to discover the first human language. If we don’t look to science for all the answers, we can protect its reputation by keeping it separate from speculation, as Klymkowsky hopes.

* Note: Carl Woese (1928–2012), who first classified the archaea, doubted it was that simple but it’s a story for another day
Comment:

See also: Last universal common ancestor was “a sophisticated cellular organism”

Earliest pre-life depended on horizontal gene transfer?

and

Evolution vs common descent, universal common descent

10 Replies to “Molecular biologist: Speculation re the last universal common ancestor is not helping science

  1. 1
    Nonlin.org says:

    The concept of LUCA makes no sense. What was so special about LUCA that we can’t see it happen again and again? Yet we don’t.
    http://nonlin.org/warmpond/
    Darwin’s “four or five” (LUCAs) make even less sense and of course was based on nothing.

  2. 2
  3. 3
    goodusername says:

    What was so special about LUCA that we can’t see it happen again and again? Yet we don’t.

    What? By definition, there can only be one LUCA.

  4. 4
    Seversky says:

    Nonlin.org @ 1

    The concept of LUCA makes no sense. What was so special about LUCA that we can’t see it happen again and again? Yet we don’t

    What was so special about your grandmother that you don’t see her happening again and again? Yet you don’t.

  5. 5
    Bob O'H says:

    goodusername – there could have been more than one origin of life, but (a) the “life” would probably look very different, and (b) they would almost certainly compete, so I would guess that there would be a fair chance that only one would survive.

  6. 6
    Nonlin.org says:

    goodusername,

    Nature doesn’t have to obey your definitions. Why do I have to explain this?

    Seversky,

    Yet there are many grandmothers out there. LUCA is not about one particular organism. Why do I have to explain this?

    Bob O’H,

    You’re making up a baseless scenario. Why would you think “only one would survive”? That’s not what we see in nature – think bear and wolf overlapping territory.

  7. 7
    ET says:

    Bob O’H:

    there could have been more than one origin of life

    Not without an Intelligent Designer. Without that you won’t even have one OoL.

  8. 8
    ET says:

    It also needs to be noted that there isn’t a materialistic mechanism capable of producing eukaryotes.

  9. 9
    OLV says:

    They’re trying hard to figure it out the next few days:

    http://www.evodevo2018.eu/ehom.....8/Welcome/

    Poor things. Totally oblivious.

    Last year they didn’t have much evo talk in the evo-devo presentations.

    Let’s see how they do this year. Maybe the scenic Irish beauty around will inspire them to come up with better just so fairytales?

  10. 10
    OLV says:

    ET (8):
    They might find it soon
    See the news at #9

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