Origin of Life

[Mott the Hoople]

Not a bad point, but the caveat is that only hydrogen and helium condensed from the big bang. Carbon, phosphorus, nitrogen, and associated organic compounds ultimately were manufactured in super novas.

The problem is not with the building blocks of life - organic compounds are ubiquitous in the universe. The challenge is how did these molecules assemble themselves into exceedingly complex, self-replicating cells. Even after 70 years of intensive study, it remains a mystery.

It’s no mystery to me. Beer is the catalyst for most reproduction.

 

[Mott the Hoople]

What came first; the chicken or the egg????????????????????

The egg. Wouldn’t you come first if you were getting laid?

 

[Mott the Hoople]

A good contribution.

My response is that, as far as we know, space and time are not infinite. We can measure the distance to the cosmic background microwave radiation (CMB), which is presumed to be the limit of the observable universe. According to theoretical physics the CMB represents 400,000 years after the big bang, when photons were able to freely move through the universe.

That places constraints on the size and age of the universe.

13.8 billion years is still a lot if time for biological evolution to occur in the cosmos, if it did.

I keep coming back to the wierd fact that life only evolved once on earth. Every living thing today is a genetic descendent of the first microbes of 3.8 billion years ago. The earth had been around more than 4 billion years, that is almost a third of the age of the universe. If we assume life is so cosmically ubiquitous and resilient, why did life only evolve one time on earth? Why are we not seeing multiple evolutionary events of exotic life forms and life forms of an entirely different genetic heritage?

To me, it either means the evolution of life is an exceedingly rare event; or DNA-based life is the only realistically possible form of life; or maybe ancient Earth did have multiple evolutionary events but we have just not seen the evidence.

I think Carl Sagan said it very well when he said space/time are finite but boundless.

 

[Mott the Hoople]

Given the set of chemicals life has to work with on this planet, maybe that's the only possibility -- one original life form?

That would be unequivocally wrong. We definitely have evidence that life began simultaneously with a wide variety of stem cells.

 

[Mott the Hoople]

Agree. There is likely to be life in other places, maybe with a different chemical base depending on what is available.

We want to believe that we're special, unique. I'm not sure that that's true.

Absolutely. Just don’t clean your refrigerator for three years and you can observe that first hand. LOL

 

[NiftyNiblick]

I don't understand the concepts of backwards infinity and, for that matter, absolute origins.

No matter what we identify as an origin of some kind, then what came before that?

I can't imagine any concepts that don't recognize time sequence, even if there's no reference on which to base the time.

Forward infinity is easy to understand.
More of the same shit forever. Forward infinity is as depressing as it gets. That's why I don't allow myself to believe in an eternal afterlife.
The perfect peace of non-existence is all the reward that any of us need.

Every attempt at an explanation for backwards infinity, however, sounds fanciful and heavy with subjective rather than objective concepts.
I just can't grasp it. I can't grasp the concept of time not existing. As long as the word "before" continues to exist, it's always there to ask about.

 

[Mott the Hoople]

Okay, you want to believe that it all happened by random chance on the basis of known chemistry, biology, and physics. I added in the possibility that someone deliberately stirred the witch's caldron to make it happen. It's certainly possible there is other intelligent life in the universe. I'm not counting that out as a possibility, no "hocus pocus" involved.

That’s just completely untrue. In fact it’s the exact opposite. Events in nature do occur randomly but they are all still subject to the laws of chemistry, biology and physics. Those are anything but random.

 

[Mott the Hoople]

^ I include that under category 1).
To me, life evolving through an intelligent agency, versus life evolving by miraculous intervention is a distinction without a difference.

Agreed.

 

[Mott the Hoople]

We really don't know if it is miraculous. For all we know, some intelligent species has done this in a whole bunch of places for whatever reason. We also don't know how we'd stack up with other intelligent species elsewhere in the universe since we have yet to meet any.

Well that’s fine to believe in but that philosophy falls outside the scope of science until someone can provide empirical evidence that identifies that intelligence. That hasn’t happened to date.

 

[Mott the Hoople]

For sure.

Maybe DNA-based life is the only plausible form of life for Earth's environment.

But four billion years is a long time, and if the laws of chemistry and physics are so conducive to the emergence of life, it just seems a little weird that in all that vast depth of time life only evolved once, and it evolved based on deoxyribonucleic acid.

If I were working in the fields of abiogenesis and astrobiology, these would be my working hypotheses:


In four billion years, life only evolved once on earth, suggesting that the evolution of life is rare and requires a series of highly unlikely chemical and physical reactions.

Maybe DNA-based life is the only plausible form of life (this seems a little weird given how complex and versatile carbon chemistry is).

Maybe environmental conditions on earth for some reason inevitably lead to DNA-based life.

Maybe life evolved more than once on earth, but we just have not seen, or looked for the evidence.

I would say those are poor hypothesis to start with;

Hypothesis #1. Biological evolution of life is anything but rare and we observe it constantly and the evidence for the vast quantity of speciation is proof that the complex chemical and physical reactions necessary are very much likely to happen because it has happened.

Hypothesis #2. At best a weak hypothesis as RNA based viruses come very close to falsifying this hypothesis.

hypothesis #3. That question has already been answered. It did lead inevitably to DNA based life. Don’t believe me? Go look in the mirror. That’s all the evidence you need to independently verify that fact.

Hypothesis #4. Maybe you need to rephrase this hypothesis because as phrased that has been falsified as life evolves constantly on earth and that has been observed from many sources of evidence both looked for and unlooked for. New life forms constantly begin new species which inevitably go extinct and the evolution begins all over again with new species.

 

[Mott the Hoople]

Evidence currently states life only evolved on Earth.

True but we can only say that because we are limited to traveling only within our Solar System.

 

[Mott the Hoople]

Yes, this whole topic is sheer speculation, but arm waving and conjecture is a fun part of the scientific tradition.

And important. Most great ideas of science don’t start with a hypothesis but start with conjecture.

 

[Mott the Hoople]

Out of the zillions of known galaxies you think there's only one planet that life inhabits?

Well given human behavior I think that’s strong evidence that intelligent life does not exist anywhere in the Universe.

 

[NiftyNiblick]

I have no detailed theories concerning the beginning of matter,
but I do have a pretty strong opinion that it was, as things turned out, a really bad idea.

 

[Mott the Hoople]

What makes you think there's proof of life here on Earth?

The Yankees losing the ALC.

 

[Mott the Hoople]

Supernovae are not uncommon so we're back to nothing unusual about Earth. I understand your question but I've also read through the rest of the thread and there are a couple of points that I have some thoughts on.

1) Why has life not re-emerged?

I'm not a super-scientist but my guess is that the conditions necessary for the emergence of life are not the same as the conditions necessary for the flourishing of life...IOW the emergence of life guarantees life won't emerge again.

2) It took 4 billion years for advanced life to come to be.

We actually don't know this to be true. Anything older than 18,000 years is most likely under about 600 feet of water so there's a lot we don't know about our past. We do not have eyes to see.

Another question, and a good one, is how did intelligent life evolve at all? I don't know, but it did and I doubt that is unique because if it happened once it assuredly happened more than once, perhaps not on Earth but the Universe is a big sandbox.

For a non scientist those are very good points/questions.

 

[Mott the Hoople]

Is "4 billion" just a marker of scale or do they literally mean 4 Billion year ago??

Both.

 

[Mott the Hoople]

Only idiots conclude such a thing. The fact remains Earth is the only place with evidence of life. No projections please.

You have absolutely no idea how much it pains me to say this or the degree of pain involved but PmP is right.

 

[Mott the Hoople]

that is why I am one of the few on the thread to suggest life in the galaxy might be rare; I am erring on the side of caution, and recognizing that the jump from organic molecules to complex, self-replicating microbes was a one-time event on Earth in its 4.5 billion year history.

Lacking the ability for interstellar travel, our best bet may be to look for biosignatures in the atmospheres of Earth-like exoplanets, like free oxygen.. We should have that capability in the next decade.

I am not ruling out extinct or current microbial life on Mars, the moons of Saturn and Jupiter. I am just not going to get my hopes up too high

I disagree with this because we lack the ability to, in principle, falsify this hypothesis. Not until we advance to a state where we can travel in space outside our solar system making it impossible, at this time, to either verify or falsify this hypothesis.

 

[NiftyNiblick]

Evidence within the grasp of our observation cannot be assumed to be the totality of evidence existing.

On the other, pondering beyond that is an exercise not likely to yield satisfying answers.