Do we know that abiogenesis happened only once on earth? Do biologists know that all life originates from a common ancestor?

If so, is this considered a sign that abiogenesis is rare even in under generous conditions like a habitable zone?

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    $\begingroup$ No, we don't. Abiogenesis has never been observed, ever, so it must be rare. There are a lot of questions about this; searching the tag will get you plenty to chew on. :) $\endgroup$ Commented Sep 3, 2023 at 13:38
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    $\begingroup$ Does this answer your question? Is abiogenesis possible today? (Just one example of many.) $\endgroup$ Commented Sep 3, 2023 at 13:39
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    $\begingroup$ Also for abiogenesis to be noticed, it will have to evolve completely different structures and metabolic pathways (non-carbon based or non-DNA,non-RNA based) to avoid competition for resources. Otherwise it might also be dismissed as a result of general evolution. $\endgroup$
    – Aurelius
    Commented Sep 3, 2023 at 16:48
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    $\begingroup$ we have some evidence all extant life has the same origin due to codon mapping, but there could easily have been several competing life linages on the early earth. indeed all life extant life could come from the merging of different simple lineages. $\endgroup$
    – John
    Commented Sep 4, 2023 at 1:32
  • $\begingroup$ We don't even know IF abiogenesis happened on Earth, let alone how many times. Most evidence suggests that all Extant life on the planet evolved from a universal common ancestor, but that isn't necessarily evidence that abiogenesis is rare. For one thing, if multiple branches of life arose independently, they would likely still utilize similar resources, thus competitive exclusion could take place. And what counts as rare may also be subjective. What's rare on the scale of recorded history may not be so rare on cosmic timescales. $\endgroup$
    – MikeyC
    Commented Sep 6, 2023 at 21:23


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