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Makes me wonder, was it actually a literal "single ancestor" at any point, or are we be the result of several completely unrelated populations doing horizontal

Makes me wonder, was it actually a literal "single ancestor" at any point, or are we be the result of several completely unrelated populations doing horizontal gene transfers (or whatever it would've been before actual genes were a thing)? What little I know of what we know, it doesn't seem completely implausible to me for self-replicating molecules to have appeared multiple times on the young Earth. Is it possible for these hypothetical multiple starts to have been be chemically compatible?

PaulHoule 7y ago
There was a huge horizontal gene transfer event when us Eukaryotes were born from a train crash between the Bacteria and the Eubacteria. Thus you can't trace out a single "tree" of life all the way to the root.
- chousuke 7y ago
  I'm vaguely aware of that, but I was thinking about life even earlier. That is, instead of having a single universal common ancestor to all life that currently exists, would it have been possible to have a set of separate strands of life that arose from abiogenesis (or however it started) and later merged? I like the thought, though I'm aware that that alone doesn't make it more likely to be true. I'm just wondering if we know something that rules out the possibility.
  - tempguy9999 7y ago
    > to have a set of separate strands of life that arose from abiogenesis (or however it started) and later merged? Not impossible but likely ever impossible to prove. I have read a theory that in the earliest days before impermeable cell walls formed, all dna (or whatever it was then) was being madly swapped around because horizontal transfer couldn't be stopped. No lineage then, but an amorphous glob of all life. When life got more sophisticated it then differentiated, because it could block horizontal transfer. But again, who knows.
    - deleted 7y ago
      [deleted]
    - TeMPOraL 7y ago
      'Madly swapping DNA around' happens to this day at the bacterial/archaeal level. The argument against multiple "strands" of life is simple: if abiogenesis of a single replicator is extremely improbable, abiogenesis of multiple such replicators is much less likely still. Plus, almost by definition, the first successful replicator will start replicating and eating all it can around itself, strongly altering environmental conditions and closing the doors for anything that could spontaneously arise after it.
      - tempguy9999 7y ago
        > if abiogenesis of a single replicator is extremely improbable If [0] > the first successful replicator will start replicating and eating all it can around itself Assuming such life looked much like it does now, yes. It may, it may not. I'm not disagreeing with you, these are valid points but we can't know and I am uneasy about speculating in such a case. [0] https://en.wikipedia.org/wiki/Laconic_phrase https://en.wikipedia.org/wiki/Laconic_phrase After invading southern Greece and receiving the submission of other key city-states, he [Philip II of Macedon] turned his attention to Sparta and asked menacingly whether he should come as friend or foe. The reply was "Neither." Losing patience, he sent the message: "You are advised to submit without further delay, for if I bring my army into your land, I will destroy your farms, slay your people, and raze your city" The Spartan ephors again replied with a single word: "If"
chrischattin 7y ago
If you're interested in this stuff, you should check out the book "The Vital Question" by Nick Lane. It's an absolutely fascinating exploration of this topic. Blew my mind. Basically, as best we know now life did have a common ancestor in ancient bacteria and there was a split at some point into eukaryotic bacteria/cells leading to more complex life.
lioeters 7y ago
I believe "LUCA" fits the description: the last universal common ancestor from which all organisms now living on Earth have a common descent. https://en.wikipedia.org/wiki/Last_universal_common_ancestor https://en.wikipedia.org/wiki/Last_universal_common_ancestor

PaulHoule 7y ago

There was a huge horizontal gene transfer event when us Eukaryotes were born from a train crash between the Bacteria and the Eubacteria. Thus you can't trace out a single "tree" of life all the way to the root.

chousuke 7y ago
I'm vaguely aware of that, but I was thinking about life even earlier. That is, instead of having a single universal common ancestor to all life that currently exists, would it have been possible to have a set of separate strands of life that arose from abiogenesis (or however it started) and later merged? I like the thought, though I'm aware that that alone doesn't make it more likely to be true. I'm just wondering if we know something that rules out the possibility.
- tempguy9999 7y ago
  > to have a set of separate strands of life that arose from abiogenesis (or however it started) and later merged? Not impossible but likely ever impossible to prove. I have read a theory that in the earliest days before impermeable cell walls formed, all dna (or whatever it was then) was being madly swapped around because horizontal transfer couldn't be stopped. No lineage then, but an amorphous glob of all life. When life got more sophisticated it then differentiated, because it could block horizontal transfer. But again, who knows.
  - deleted 7y ago
    [deleted]
  - TeMPOraL 7y ago
    'Madly swapping DNA around' happens to this day at the bacterial/archaeal level. The argument against multiple "strands" of life is simple: if abiogenesis of a single replicator is extremely improbable, abiogenesis of multiple such replicators is much less likely still. Plus, almost by definition, the first successful replicator will start replicating and eating all it can around itself, strongly altering environmental conditions and closing the doors for anything that could spontaneously arise after it.
    - tempguy9999 7y ago
      > if abiogenesis of a single replicator is extremely improbable If [0] > the first successful replicator will start replicating and eating all it can around itself Assuming such life looked much like it does now, yes. It may, it may not. I'm not disagreeing with you, these are valid points but we can't know and I am uneasy about speculating in such a case. [0] https://en.wikipedia.org/wiki/Laconic_phrase https://en.wikipedia.org/wiki/Laconic_phrase After invading southern Greece and receiving the submission of other key city-states, he [Philip II of Macedon] turned his attention to Sparta and asked menacingly whether he should come as friend or foe. The reply was "Neither." Losing patience, he sent the message: "You are advised to submit without further delay, for if I bring my army into your land, I will destroy your farms, slay your people, and raze your city" The Spartan ephors again replied with a single word: "If"

chrischattin 7y ago

If you're interested in this stuff, you should check out the book "The Vital Question" by Nick Lane. It's an absolutely fascinating exploration of this topic. Blew my mind. Basically, as best we know now life did have a common ancestor in ancient bacteria and there was a split at some point into eukaryotic bacteria/cells leading to more complex life.

lioeters 7y ago

I believe "LUCA" fits the description: the last universal common ancestor from which all organisms now living on Earth have a common descent. https://en.wikipedia.org/wiki/Last_universal_common_ancestor https://en.wikipedia.org/wiki/Last_universal_common_ancestor