The evolution of complex life

[Cypress]

Agreed. Let me know if you want to talk about the chemistry since that's essentially the topic at hand.

70 percent of what I know about origin of life research comes from Robert Hazen, a well regarded abiogenesis researcher.

This is basically his money quote on this scientific topic:

"The great mystery of life’s origins lies in the gap between simple organic molecules and primitive cells."

Robert Hazen

 

[Saint Guinefort]

70 percent of what I know about origin of life research comes from Robert Hazen, a well regarded abiogenesis researcher.

This is basically his money quote on this scientific topic:

Cool.

 

[Dutch Uncle]

70 percent of what I know about origin of life research comes from Robert Hazen, a well regarded abiogenesis researcher.

This is basically his money quote on this scientific topic:

"The great mystery of life’s origins lies in the gap between simple organic molecules and primitive cells."

Robert Hazen

That gap is certainly a mystery since life hasn't been found anywhere but Earth and can't be replicated by science...yet. Maybe never.

 

[Saint Guinefort]

That gap is certainly a mystery since life hasn't been found anywhere but Earth and can't be replicated by science...yet. Maybe never.

To be quite fair we've looked in vanishingly few places. So to claim it hasn't been found anywhere but earth is quite limited in value.

In addition we tend to look for life using relatively crude proxies.

 

[Dutch Uncle]

To be quite fair we've looked in vanishingly few places. So to claim it hasn't been found anywhere but earth is quite limited in value.

In addition we tend to look for life using relatively crude proxies.

The Drake Equation and Fermi's Paradox indicate they should be finding us.

 

[Saint Guinefort]

The Drake Equation and Fermi's Paradox indicate they should be finding us.

I am not necessarily talking about intelligent life that has achieved the ability to broadcast their existence.

I'm talking about life qua life.

And besides, the Drake Equation has a lot of "fudgefactors" or unknowable quantities as of this time.

 

[Cypress]

That gap is certainly a mystery since life hasn't been found anywhere but Earth and can't be replicated by science...yet. Maybe never.

I am hopeful that in decades to come, the transition between inert prebiotic molecules and cellular life will come into clearer focus.

At the same time, I don't think a responsible scientist should leap to conclusions. We can't yet rule out the possibility that life was a result of a perfect storm of a series of unusual chemical steps which are unlikely to be replicated in a lab.

 

[Saint Guinefort]

I am hopeful that in decades to come, the transition between inert prebiotic molecules and cellular life will come into clearer focus.

What counts as "pre-biotic"?

At the same time, I don't think a responsible scientist should leap to conclusions. We can't yet rule out the possibility that life was a result of a perfect storm of a series of unusual chemical steps which are unlikely to be replicated in a lab.

Define "unusual".

Maybe I'm getting too hung up on the chemistry technical information but I'm seeing a lot of loose language that papers over possibly deeper flaws. What do you mean by "unusual chemical steps"?

 

[Dutch Uncle]

I am not necessarily talking about intelligent life that has achieved the ability to broadcast their existence.

I'm talking about life qua life.

And besides, the Drake Equation has a lot of "fudgefactors" or unknowable quantities as of this time.

The question remains: in a galaxy of a 100 thousand million stars, why aren't there any signs of life out there?

https://www.esa.int/Science_Explora...chel/How_many_stars_are_there_in_the_Universe

If life is just chemistry, why can't you whip up a batch?

 

[Saint Guinefort]

The question remains: in a galaxy of a 100 thousand million stars, why aren't there any signs of life out there?

It appears you are assuming that our failure to, in the space of what, maybe 60 years now, find evidence of an advanced civilization which could broadcast it's existence means there is likely no life out there? Is the development of radio broadcast capability the measure of "life"?

No, the fact of the matter is we have found lots of organic molecules that are used by living things all over the place. We have meteorites carrying isolated amino acids and sugars. So why would you assume there ISN'T life just because we haven't found a life form that has developed radio or other broadcast means?

And spectroscopically I honestly don't see how you could look at an entire planet and draw a conclusion about it's potential life forms. In fact many of the "planets" we know of outside of our solar system are essentially inferred by gravitational effects on larger objects. So it's not like we are in any way REALLY looking.

Right now suggesting that life is "rare" in the cosmos is a relatively weak and unevidenced position.

 

[Dutch Uncle]

I am hopeful that in decades to come, the transition between inert prebiotic molecules and cellular life will come into clearer focus.

At the same time, I don't think a responsible scientist should leap to conclusions. We can't yet rule out the possibility that life was a result of a perfect storm of a series of unusual chemical steps which are unlikely to be replicated in a lab.

Not a chemist or biologist, but I do know results count.

The odds favor life being found elsewhere in the Universe. A major mystery is "Why haven't we seen signs of it?"

The oldest stars in our galaxy are over 13B years old. Our star is only 4.6B years old. That's a huge gap in time for life to pop into existence and evolve into civilizations. So where are they?

There are theories, but the lack of evidence is astounding given the amount of time and number of stars involved.

https://en.wikipedia.org/wiki/List_of_oldest_stars

 

[Dutch Uncle]

It appears you are assuming that our failure to, in the space of what, maybe 60 years now, find evidence of an advanced civilization which could broadcast it's existence means there is likely no life out there? Is the development of radio broadcast capability the measure of "life"?

No, the fact of the matter is we have found lots of organic molecules that are used by living things all over the place. We have meteorites carrying isolated amino acids and sugars. So why would you assume there ISN'T life just because we haven't found a life form that has developed radio or other broadcast means?

And spectroscopically I honestly don't see how you could look at an entire planet and draw a conclusion about it's potential life forms. In fact many of the "planets" we know of outside of our solar system are essentially inferred by gravitational effects on larger objects. So it's not like we are in any way REALLY looking.

Right now suggesting that life is "rare" in the cosmos is a relatively weak and unevidenced position.

You habitually leap to conclusions and then project that habit onto others.

The fact remains results count. Evidence counts. Sure, an absence of evidence is not evidence of absence, but the fact remains we've both been looking for life across our galaxy and in the lab with no results since Galileo first made a telescope.

 

[Saint Guinefort]

You habitually leap to conclusions and then project that habit onto others.

The fact remains results count. Evidence counts. Sure, an absence of evidence is not evidence of absence, but the fact remains we've both been looking for life across our galaxy and in the lab with no results since Galileo first made a telescope.

And how do you think life is "Detected"?

Life is NOT limited ONLY to those things which have the ability to create radiowaves or do interplanetary exploration. THOSE would be literally the ONLY things we could have detected apart from our brief foray onto the surface of Mars and Venus.

But that isn't all of life, is it? My dog can't broadcast his existence with radio waves and he can't build a rocket to travel interstellar distances, but I think we'd both agree he's complex life.

That's my point. The universe may literally be LOUSY with life. And there would be NO WAY for us to know it is out there.

How do you think life is detected on extrasolar planets? The fact of the matter is it isn't even possible to test for it unless it is so technologically advanced it independently developed radio wave generation.

What if some planet out in the cosmos is crawling with plants and animals like earth was for several billion years before the advent of humans and their radio frequency broadcasts.?

Would anyone observing from many many light years away have a CLUE as to our planet's status as a life-bearing planet? How would they do that?

 

[Dutch Uncle]

And how do you think life is "Detected"?

Life is NOT limited ONLY to those things which have the ability to create radiowaves or do interplanetary exploration. THOSE would be literally the ONLY things we could have detected apart from our brief foray onto the surface of Mars and Venus.

But that isn't all of life, is it? My dog can't broadcast his existence with radio waves and he can't build a rocket to travel interstellar distances, but I think we'd both agree he's complex life.

That's my point. The universe may literally be LOUSY with life. And there would be NO WAY for us to know it is out there.

How do you think life is detected on extrasolar planets? The fact of the matter is it isn't even possible to test for it unless it is so technologically advanced it independently developed radio wave generation.

What if some planet out in the cosmos is crawling with plants and animals like earth was for several billion years before the advent of humans and their radio frequency broadcasts.?

Would anyone observing from many many light years away have a CLUE as to our planet's status as a life-bearing planet? How would they do that?

The same way Stephen Hawking warned us about, "via the radio and TV signals that humanity has been sending out into space since 1900".

If humans didn't exist on Earth, would some other lifeform had advanced enough to communicate with radio signals?

https://www.space.com/34184-stephen-hawking-afraid-alien-civilizations.html

For what it's worth, some other astronomers believe Hawking's caution is unwarranted. Any alien civilization advanced enough to come to Earth would surely already know of humans' existence via the radio and TV signals that humanity has been sending out into space since 1900 or so, this line of thinking goes.

 

[Saint Guinefort]

The same way Stephen Hawking warned us about, "via the radio and TV signals that humanity has been sending out into space since 1900".

I disagree with your definition of "life". In my definition life can still exist even if it lacks the ability to generate radio and tv signals.

I have a planet's worth of evidence to support my position.

 

[Dutch Uncle]

I disagree with your definition of "life". In my definition life can still exist even if it lacks the ability to generate radio and tv signals.

I have a planet's worth of evidence to support my position.

You're leaping to conclusions again, Perry PhD.

Yes, life can exist without intelligence and radios. However, life continues to evolve over time. Given enough time, those evolving lifeforms will advance enough to leave their planet, which means they'll use the natural laws of the Universe to communicate.

You are free to believe that out of 100 thousand million stars, only humans invented radio communications, but I disagree.

 

[Cypress]

Not a chemist or biologist, but I do know results count.

The odds favor life being found elsewhere in the Universe. A major mystery is "Why haven't we seen signs of it?"

The oldest stars in our galaxy are over 13B years old. Our star is only 4.6B years old. That's a huge gap in time for life to pop into existence and evolve into civilizations. So where are they?

There are theories, but the lack of evidence is astounding given the amount of time and number of stars involved.

https://en.wikipedia.org/wiki/List_of_oldest_stars

It might be a possibility that intelligent life capable of technology is exceedingly rare, we might be the only example of it in this galaxy. Primitive cellular life might possibly be more commonplace.

When we were told in high school that the Earth is an average planet around an average star, that might not actually be correct. Our star is quite unusual in a number of ways, it's not a binary system, it's more enriched in heavy elements, its more massive and it's much younger than 90 percent of stars.

Earth might be unsual for a terrestrial planet, with it's combination of a strong magnetic field, and large lunar cycle companion, and protected by Jupiter from frequent cosmic asteroid strikes.

 

[Dutch Uncle]

It might be a possibility that intelligent life capable of technology is exceedingly rare, we might be the only example of it in this galaxy. Primitive cellular life might possibly be more commonplace.

When we were told in high school that the Earth is an average planet around an average star, that might not actually be correct. Our star is quite unusual in a number of ways, it's not a binary system, it's more enriched in heavy elements, its more massive and it's much younger than 90 percent of stars.

Earth might be unsual for a terrestrial planet, with it's combination of a strong magnetic field, and large lunar cycle companion, and protected by Jupiter from frequent cosmic asteroid strikes.

While I agree it's possible, I think the natural laws of the Universe, including evolution of life, would apply to those other planets. As Perry pointed out previously, there are non-life building blocks found off planet such as amino acids.

Again, not a chemist but my understanding is that life is mostly likely to be either carbon-based or silicon-based. If true, then it follows that extraterrestrial carbon-based lifeforms would evolve much like life has on Earth....although not necessarily mammalian. If an impact event hadn't laid waste to the planet, would intelligent reptiles have evolved?

 

[Saint Guinefort]

You are free to believe that out of 100 thousand million stars, only humans invented radio communications, but I disagree.

But you see my point, right? Life doesn't have as a requirement "the ability to generate radio waves", right? I'm sure you see that point. Life qua life does NOT require any ability to create radio wave broadcasts.

I get that you think that life, given enough time, will eventually create radio broadcasts, but even that's not necessarily likely by the evidence from the single example we have. Humans existed for 99.9999999999% of their tenure on this planet and never had the ability to generate a radio wave, let alone one strong enough to create a coherent detectable signal several light years away from the earth.

And if you put all the complex life that came before you have approximately 3.8 to 4 billion years of life (that's almost all of the entire planet's history) that would be completely undetectable by outside observers.

 

[Cypress]

It appears you are assuming that our failure to, in the space of what, maybe 60 years now, find evidence of an advanced civilization which could broadcast it's existence means there is likely no life out there? Is the development of radio broadcast capability the measure of "life"?

No, the fact of the matter is we have found lots of organic molecules that are used by living things all over the place. We have meteorites carrying isolated amino acids and sugars. So why would you assume there ISN'T life just because we haven't found a life form that has developed radio or other broadcast means?

And spectroscopically I honestly don't see how you could look at an entire planet and draw a conclusion about it's potential life forms. In fact many of the "planets" we know of outside of our solar system are essentially inferred by gravitational effects on larger objects. So it's not like we are in any way REALLY looking.

Right now suggesting that life is "rare" in the cosmos is a relatively weak and unevidenced position.

Organic compounds are ubiquitous in the universe. The presence of organic molecules doesn't prove anything about life.

But getting from simple molecules like amino acids and sugars to complex proteins and self replicating cells is a huge leap that we have never replicated in the lab or observed spontaneously occurring in nature. That is a subject for future research

We might be able to remotely observe evidence of life on explanets by spectrographic analysis of oxygen and methane in their atmospheres, assuming we could rule out non biogenic sources of free oxygen and CH4.