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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
(Score: 3, Interesting) by Immerman on Wednesday October 05 2022, @08:32PM (5 children)
As far as we know, there's absolutely no reason to expect later-spawning life to survive. New life could be spawning every day on Earth, but it would have no chance to survive in competition with life that's already been optimized by billions of years of evolution.
And that'd be just as true after a thousand years of evolution. The only way a new form of protolife that just barely figured out imperfect self replication could compete with life that's been around for a while is if it had a *huge* innate advantage. And if it had such a dramatic advantage, then it would be reasonably expected to rapidly outcompete all pre-existing life once it had time to start evolving a few improvements. Resulting in exactly the same fossil record as if life had only arisen once.
(Score: 2) by mcgrew on Thursday October 06 2022, @04:07PM (4 children)
There was a billion years of life on Earth before evolution started 750 million years ago.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by Immerman on Thursday October 06 2022, @04:34PM (3 children)
What?
The first (definite) animals evolved around 750M years ago, but evolution started immediately after the first self-replicating pre-biotic systems started replicating 4+ billion years ago.
There's nothing magical or animal-specific about evolution - it's just the inevitable result of imperfect replication and death due to environmental factors.
(Score: 2) by mcgrew on Tuesday October 11 2022, @06:04PM (2 children)
Not according to that scientist, who studies ancient organisms. Life began, according to her, one billion seven hundred fifty years ago and didn't start evolving until life had been here for a billion years. Note by "life" it's not viruses, which aren't really alive, since they need a host to replicate. Oh, and if it's not alive it can't die, even if, like an automobile, it can seem to be alive ("it's dead, Jim." "Well, hold on... try it now).
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by mcgrew on Tuesday October 11 2022, @06:26PM (1 child)
Correction: one billion seven hundred fifty MILLION years.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by Immerman on Tuesday October 11 2022, @08:57PM
Citation?
Here's one of mine, with a links to many others: https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life [wikipedia.org]
If one scientist says something, they're probably wrong. Something like 80-90% of all published studies are later disproven - that's the whole point of peer review. And why you should take everything with a grain of salt until a concsensus of scientists agrees that something is true after it has withstood extensive challenges by experts in related fields.