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posted by janrinok on Wednesday October 05 2022, @05:35AM   Printer-friendly
from the out-with-the-old-priors-and-in-with-the-new dept.

New Theory Concludes That the Origin of Life on Earth-Like Planets Is Likely:

Does the existence of life on Earth tell us anything about the probability of abiogenesis — the origin of life from inorganic substances — arising elsewhere? That's a question that has confounded scientists, and anyone else inclined to ponder it, for some time.

A widely accepted argument from Australian-born astrophysicist Brandon Carter argues that the selection effect of our own existence puts constraints on our observation. Since we had to find ourselves on a planet where abiogenesis occurred, then nothing can be inferred about the probability of life elsewhere based on this knowledge alone.

[...] However, a new paper by Daniel Whitmire, a retired astrophysicist who currently teaches mathematics at the U of A, is arguing that Carter used faulty logic. Though Carter's theory has become widely accepted, Whitmire argues that it suffers from what's known as "The Old Evidence Problem" in Bayesian Confirmation Theory, which is used to update a theory or hypothesis in light of new evidence.

[...] As he explains, "One could argue, like Carter, that I exist regardless of whether my conception was hard or easy, and so nothing can be inferred about whether my conception was hard or easy from my existence alone."

In this analogy, "hard" means contraception was used. "Easy" means no contraception was used. In each case, Whitmire assigns values to these propositions.

Whitmire continues, "However, my existence is old evidence and must be treated as such. When this is done the conclusion is that it is much more probable that my conception was easy. In the abiogenesis case of interest, it's the same thing. The existence of life on Earth is old evidence and just like in the conception analogy the probability that abiogenesis is easy is much more probable."

Journal Reference:
Daniel P. Whitmire. Abiogenesis: the Carter argument reconsidered [open], Int J Astrobio, 2022. DOI: 10.1017/S1473550422000350


Original Submission

 
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  • (Score: 3, Informative) by mcgrew on Wednesday October 05 2022, @06:30PM (1 child)

    by mcgrew (701) <publish@mcgrewbooks.com> on Wednesday October 05 2022, @06:30PM (#1275071) Homepage Journal

    Why is this incredibly weak hypothesis being called a theory? From TFA:

    At best, he argued, the knowledge of life on Earth is of neutral value. Another way of looking at it is that Earth can’t be considered a typical Earth-like planet because it hasn’t been selected at random from the set of all Earth-like planets.

    Not random? Am I dim today or is the author not communicating well?

    As I've said before, until we have a clue about HOW abiogenesis started, and what conditions were necessary to to start, we will remain clueless about how numerous, scarce, or nonexistent life is outside our solar system. Fictional examples:
    http://mcgrewbooks.com/Voyage/Contact.html [mcgrewbooks.com]
    https://www.mit.edu/people/dpolicar/writing/prose/text/thinkingMeat.html [mit.edu]
     

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  • (Score: 3, Informative) by Immerman on Thursday October 06 2022, @02:14PM

    by Immerman (3985) on Thursday October 06 2022, @02:14PM (#1275239)

    Any data source pre-screened by any selection criteria is no longer truly random, and thus can't be assumed to be at all representative of the larger population.

    For example: if you perform a random phone survey you'll find that roughly 100% of people own phones, even if only 1% actually do. That's one of the reasons that online surveys are generally regarded as unsuitable for most scientific purposes - you're pre-screening your sample population to include only those people from the target population that have internet access, visit someplace your survey is advertised, and are inclined to take online surveys - a subset that is extremely unlikely to be a representative sample of the larger population.

    Similarly, if you survey a bunch of Earth-like planets with life on them (or just one) they tell you nothing about Earth-like planets in general, only about the pre-screened subset of Earth-like planets with life. Or in our case, specifically Earthlike planets that gave rise to intelligent, technological societies - which may be very atypical even among life-bearing worlds.

    And since we can look around and see three other Earth-like planets (and over a dozen Earth-like moons) in our solar system that have no (obvious) life on them, we can be fairly confident in saying that Earth's vibrant ecology is NOT typical of Earth-like plant(oid)s.