The evolution of complex life

Doc Dutch said:
Agreed the research indicates all life on Earth is traced back to LUCA. My points of disagreement were asserting it as evidence of abiogenesis and that it was the only form of life on Earth to exist at the time or previously.

I'm not asserting "divine intervention" unless people want to include space aliens taking a dump on a sterile Earth as "divine intervention". I'm only saying I don't know and the facts, as presented, are not proof about the origin of LUCA.
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My thought on others independent lines of life occurring before or during the time of LUCA is that it seems to beg the question of why they would disappear?

We've been told since 7th grade science class that life is tenacious and clings to a toehold. But now we're going to say multiple lines of biological life arose and then disappeared, leaving only LUCA.

Maybe that happened, but it raises additional questions.

It's obviously perfectly reasonable to assert we are largely in the dark about what events transpired between LUCA and the primordial prebiotic chemistry, without invoking miracles or dieties.

The whole topic tends to get pigeonholed between the intelligent design holy rollers, and the strictly materialistic atheists.
 
Cypress said:
My thought on others independent lines of life occurring before or during the time of LUCA is that it seems to beg the question of why they would disappear?

We've been told since 7th grade science class that life is tenacious and clings to a toehold. But now we're going to say multiple lines of biological life arose and then disappeared, leaving only LUCA.

Maybe that happened, but it raises additional questions.

It's obviously perfectly reasonable to assert we are largely in the dark about what events transpired between LUCA and the primordial prebiotic chemistry, without invoking miracles or dieties.

The whole topic tends to get pigeonholed between the intelligent design holy rollers, and the strictly materialistic atheists.
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Extinction of species is a part of evolution. Maybe the planet became too cold, too hot, too acidic or too base for other species, leaving only LUCA the survivor.

In 7th grade I never heard of LUCA....and computers were well beyond private ownership due to immense size and cost.

Agreed we are in the dark about how life arose on Earth. What we do seem to know is that all current life on Earth sprung from LUCA.

Limited minds see in Black & White, pigeonholing answers to complex questions as Either Or. Broader minds see the width and breadth of the panoply....even if only fuzzily.

Socially, it's like being forced to choose White culture or Black culture, not just maximize one's culture.
 
Doc Dutch said:
Extinction of species is a part of evolution. Maybe the planet became too cold, too hot, too acidic or too base for other species, leaving only LUCA the survivor.

In 7th grade I never heard of LUCA....and computers were well beyond private ownership due to immense size and cost.

Agreed we are in the dark about how life arose on Earth. What we do seem to know is that all current life on Earth sprung from LUCA.

Limited minds see in Black & White, pigeonholing answers to complex questions as Either Or. Broader minds see the width and breadth of the panoply....even if only fuzzily.

Socially, it's like being forced to choose White culture or Black culture, not just maximize one's culture.
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Possibly, other clades with a different last common ancestor went extinct around the time of LUCA @ 3.5 billion years ago.

But that still leaves billions of years for other clades of biological life to emerge. But we see no trace of it. No silicon-based biology. No other genetically distinct forms of carbon based life.

All we have is just evidence that all of the life that has ever existed descended from LUCA.

That seems a little curious, that even though there was ample geologic time and plenty of localized variation in chemical and thermal environments, we see no living or fossil evidence of a clade of organisms that go back to a different last common ancestor than LUCA.
 
Cypress said:
For somebody who supposedly just joined the board recently, you seem to have been reading a lot of my posts and stewing in resentment. I barely ever took notice of you until a week ago.

I leave you to deal with your festering grievances
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^^^^Irony.

The guy who complains when people try to discuss science he raises.

YOU are the one with grievances. I tried talking about your post on entropy but since you have ZERO scientific ability you preferred to bitch about me.

You are a piece of work. A ginormous hypocrite.

Wow. What a fuck-up.
 
Matt Dillon said:
Perry is Dutch. Accusing you of being his sock is his way of employing misdirection. He thinks he's being clever. :palm:
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At least Perry doesn't expend all his time massaging Doc's ego. Like Doc does ALL THE TIME for Cypress.

(Remember: I predicted Doc would show up when Cypress got his panties in a twist...et voila, it happened. It ALWAYS happens.)
 
Cypress said:
Possibly, other clades with a different last common ancestor went extinct around the time of LUCA @ 3.5 billion years ago.

But that still leaves billions of years for other clades of biological life to emerge. But we see no trace of it. No silicon-based biology. No other genetically distinct forms of carbon based life.

All we have is just evidence that all of the life that has ever existed descended from LUCA.

That seems a little curious, that even though there was ample geologic time and plenty of localized variation in chemical and thermal environments, we see no living or fossil evidence of a clade of organisms that go back to a different last common ancestor than LUCA.
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All excellent points. If life arose on Earth 3.5 billion years ago, why not again?
 
Perry Phimosis said:
At least Perry doesn't expend all his time massaging Doc's ego. Like Doc does ALL THE TIME for Cypress.

(Remember: I predicted Doc would show up when Cypress got his panties in a twist...et voila, it happened. It ALWAYS happens.)
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^^^
Time until Matt says "That's exactly what Dutch would say to throw everyone off": 10...9...8.....

LOL
 
Doc Dutch said:
All excellent points. If life arose on Earth 3.5 billion years ago, why not again?
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My guess is that the window of opportunity for other clades of life to arise was between 3.8 and 2.2 billion years before present. That is a 1.6 billion year window.

Once the Earth had a free oxygen atmosphere, it would have been more difficult for prebiotic chemistry to self organize into cellular life, because free oxygen O[SUB]2[/SUB] is such a highly reactive molecule.
 
Matt Dillon said:
You are Dutch's sock, not Cypress. Now I don't agree with Cypress very much, but he's a hell of a lot smarter than you, Dutch.

There's no way you could pull off pretending to be Cypress.
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Dutch knows way more than me about certain topics.

You probably know more than me about beer, football, and vintage cars.

There are no polymaths, PhDs, or truly original thinkers on this board. Internet cesspools generally don't attract the exceptionally accomplished and remarkably erudite.
 
Cypress said:
My guess is that the window of opportunity for other clades of life to arise was between 3.8 and 2.2 billion years before present. That is a 1.6 billion year window.

Once the Earth had a free oxygen atmosphere, it would have been more difficult for prebiotic chemistry to self organize into cellular life, because free oxygen O[SUB]2[/SUB] is such a highly reactive molecule.
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There are places on Earth where anaerobic life exists. That said, it's a fair point about the environment giving rise to life. I'm not sure if those same conditions exist elsewhere in our solar system.
 
Doc Dutch said:
There are places on Earth where anaerobic life exists. That said, it's a fair point about the environment giving rise to life. I'm not sure if those same conditions exist elsewhere in our solar system.
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LUCA itself was probably anaerobic or chemosynthetic because there was no appreciable free oxygen in the atmosphere or ocean until 2.2 billion years ago.

There seem to be some moons in the solar system with liquid methane, and I wonder if liquid methane could act as a solvent for alien biochemical reactions, like water does on earth. But even if it could, the kinetics of a liquid methane biological system would probably be incredibly slow because liquid methane only exists at sub zero temperatures.
 
Cypress said:
LUCA itself was probably anaerobic or chemosynthetic because there was no appreciable free oxygen in the atmosphere or ocean until 2.2 billion years ago.

There seem to be some moons in the solar system with liquid methane, and I wonder if liquid methane could act as a solvent for alien biochemical reactions, like water does on earth. But even if it could, the kinetics of a liquid methane biological system would probably be incredibly slow because liquid methane only exists at sub zero temperatures.
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It'll be awhile before we can see under the seas of Europa. The Europa Clipper is scheduled for launch in OCT24, but it's a photo reconnaissance mission, not an under ice/undersea probe.

https://www.jpl.nasa.gov/missions/europa-clipper
The mission will place a spacecraft in orbit around Jupiter in order to perform a detailed investigation of Europa -- a world that shows strong evidence for an ocean of liquid water beneath its icy crust and which could host conditions favorable for life. The mission will send a highly capable, radiation-tolerant spacecraft into a long, looping orbit around Jupiter to perform repeated close flybys of the icy moon.
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Cypress said:
There seem to be some moons in the solar system with liquid methane, and I wonder if liquid methane could act as a solvent for alien biochemical reactions, like water does on earth. But even if it could, the kinetics of a liquid methane biological system would probably be incredibly slow because liquid methane only exists at sub zero temperatures.
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Looks like a group in Sweden have put the kibosh on acrylonitrile cell walls (the alternative to phospholipid bilayers like our normal cells, hypothesized to be useful in liquid methane alternative biology, called an "azotosome") on Titan.

https://www.sciencedaily.com/releases/2020/03/200302113336.htm

"But our new research paper shows that, unfortunately, although the structure could indeed tolerate the extremes of Titan, it would not form in the first place,"
 
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Doc Dutch said:
It'll be awhile before we can see under the seas of Europa. The Europa Clipper is scheduled for launch in OCT24, but it's a photo reconnaissance mission, not an under ice/undersea probe.

https://www.jpl.nasa.gov/missions/europa-clipper
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Good times. A mission to Europa is very cool.

Enceladus might be the best prospect for detecting life in the solar system. The stories I've read suggest Enceladus has subsurface liquid water, organic molecules, and the water is known to spout out onto the surface, perhaps circumventing any need to penetrate the ice with probes.
 
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