Life on Earth arose about as soon as it was possible for life to arise

[cthulu2016]

Last edited Tue Apr 22, 2014, 01:21 AM - Edit history (2)

The first billion, billion and a half years of Earth was wall-to-wall lava and earthquakes and pretty Dante-esque. We were slammed with huge space debris all the time as our gravity cleaned up all the trash in our path that hadn't already become part of a planet. Something slammed into us so hard it knocked off a piece of Earth the size of the moon (which we today call "the moon&quot

But pretty much as soon as the Earth cooled and the in-fall of comets and asteroids stopped wrecking everything life popped up. No later than a half-billion years of when it plausibly could have, and probably sooner. (It was all bacteria type stuff at first so the fossil record is more than spotty.)

It might have popped up many times, but the life based on RNA and then DNA got established quite early on and if there were competing life modes... well, they were delicious.

We have some reason to think life is likely. Not certain, but a decent chance of popping up anywhere, given the right conditions. (Maybe Earth, our sample of one, was a super-fluke but there's no reason to assume we are exceptional.)

The right conditions are not the planetary norm, of course. Far from it. But I think that if we had some means of zipping around the universe we would find few lifeless Earth-like planets... with just powerful sunlight and water and rocks and wind. (And of the lifeless Earth-like planets we did find, how many of those would develop life in the future?)

The error in assuming that life is a fantastic long-shot comes from (in addition to people thinking we're special) underestimating the size and power of the chemical calculating engine that a lifeless ocean would be.

Without microbial life to break-up/eat exotic large hydrocarbon molecules that form and combine over time, those exotic molecules don't "die." They just keep on keepin' on, bumping into stuff and sometimes forming even longer, more exotic molecules.

It's like the lottery. Will you win? No fucking way. Forget about it.

Will somebody win? Of course. If not this week then next week... there's millions of people playing the thing.

Life on Earth is merely *somebody* winning the lottery.

[exboyfil]

1. An article to consider

http://www.technologyreview.com/view/424795/probability-of-et-life-arbitrarily-small-say-astrobiologists/

[cthulu2016]

4. I am more sympathetic to that argument vis-a-vis intelligent life

For just any old life, I don't see a great prejudice from Earth's example.

The fact that it is possible to develop life in a primordial soup churn of 300 million or 500 million years doesn't mean it is likely for life to emerge in that time frame, but it does suggest it is likely for it to emerge at all because there are so many available raffle tickets of blocks of 300 million or 500 million years.

If we didn't develop life 3.5 billion years ago then perhaps we would have done so 3.2 billion years ago, or 2.9 billion, etc.. Or 100 million years from today.

Knowing that it might start in a few hundred million years does, to me, seem to suggest that it is not a freakish occurrence when given vastly larger time frames to work with.

We don't know any side of the thing. Maybe we were super slow... maybe typical life-possible planets are exploding with life much faster than we managed. I don't think so, but arguments that we don't know general things from our sample of one cut both ways.

At heart, all of this is arbitrary. But having billions of years to do something that you know *can* be done in only hundreds of millions seems like it would be a substantial multiplier.

[exboyfil]

5. I tend to agree with you

I think ultimately we will come up with a plausible example of physical combinations that could have come about randomly that exhibits Darwinian evolution. At that point we link up chemistry with biology and complete our understanding of how life developed. From there we can extrapolate probabilities for the formation of life. I got to think that something like bacteria is ubiquitous. Eukaryotes (or its extrabiological equivalent) are probably pretty rare. Technological life is extremely rare. I think that no more than 4 technological civilizations are present in the solar system at any one time. Of course I am pulling that number and speculations out of my behind.

Lets keep looking, experimenting, and modeling though. It is an exciting time to be alive.

[Warren DeMontague]

7. As the article notes, we have a sample of exactly one, so we don't know... not yet.

However, it's also worth noting that even if "rare" or "extremely rare" or even "absurdly fucking ridiculously rare" on habitable planets, that doesn't imply we're "alone".

Life might be rare but there could still be a lot of it. The universe is BIG, and one data point we DO know now that we didn't know a few decades ago, planetary systems themselves are very common.

I think a very valid question is whether life happens all the time when conditions are favorable, (and what those conditions are, or aren't) or whether it happens once in a bleu cheese moon...

but that said, there are probably more than one bleu cheese moons in the Universe. Us being completely "alone" strikes me as the most unlikely of all the hypotheses.

[lumberjack_jeff]

2. Ward, Brownlee and Fermi are right.

http://en.wikipedia.org/wiki/Rare_Earth_hypothesis

[lumberjack_jeff]

11. ... or if a spectrometer detects oxygen on one of those extrasolar planets.

But so far the only evidence is "where is everyone?"

[jeff47]

18. How well would a person from 1000 AD hear us?

Today, we do long-range communication via radio waves.

Someone from 1000 AD could not "hear" our technology at all - they lacked the equipment to detect our communication. Similarly, we may lack the technology to "hear" more advanced species. RF is totally unsuitable for communication over interstellar distances, so an interstellar species is going to have to use something else.

Additionally, our radio waves are only strong enough to be detectable in our local neighborhood. If there is a clone of our species 250 light-years away, that was broadcasting 250 years ago, we can't hear them. The signal is too weak by the time it reaches Earth.

And to make that problem even worse, our RF is getting weaker. We peaked in about the 1960s. Since then, we have been using lower and lower power RF signals. We are using lots more RF from cell phones, wifi and the like. But the signals are about only 200mW to 2W. "Wolfman Jack" broadcasted from a 250,000W radio station.

It is extremely likely that other species went through the same RF pattern - nothing for millennia, then a very short high-powered window, followed by weaker and weaker signals. And that high-powered window only reaches a couple dozen stars before it is overwhelmed by background static.

The distances involved are so mind-bogglingly vast that it is utterly different from our Earth-bound experience.

Finally, Kepler data indicates there's roughly 40 billion planets in the habitable zones around the stars in the Milky Way alone. Even if advanced life is a 1-in-a-billion chance, that means there's about 40 advanced species in just our galaxy. But those 40 are spread out over hundreds of billions of light years. When a signal only goes about 200 light years, it's very, very unlikely that it's going to stumble across another one of the 40.

[lumberjack_jeff]

22. The universe is big, but it is also old.

Last edited Tue Apr 22, 2014, 06:46 PM - Edit history (1)

Over a period of 15 billion years an intelligent species should have spread... with robotic probes if not personally. 10,000 light years is a trivial distance if you have 100,000,000 years or more in which to do it.

[lumberjack_jeff]

30. Personally, I think we *are* the leading edge of intelligent life.

I think it's our job to export it.

[Crunchy Frog]

50. Is that sort of like an extension of the Monroe Doctrine?

I'm personally very glad that we're a long, long, long way away from being able to reach extrasolar planets.

[joshcryer]

65. Agree with this.

And I think you'd agree with my immediate earlier reply to you. It's not that life is rare, it's that highly intelligent species capable of material science are rare. Perhaps so rare the galaxy hosts maybe 2-3 of them, if that. (Outside of our galaxy they would be almost undetectable, the beacons wouldn't reach; I do have a theory that some of the heavy metal galaxies might be because some early species arose and converted it, but even that is a mere theory.)

[lumberjack_jeff]

66. Even if the galaxy hosts 2 or 3 of them at a time why have they not spread?

Over a billion years, some of those civilizations would have spread. Let's say that every 50,000 years a new technologically advanced species happens somewhere in the galaxy. I would think that at least one of those 20,000 civilizations would have sent probes and spread throughout the galaxy.

Within the next 100 years, we will have sent robotic probes to every planet in our solar system. Within the following 100 years those robots will leave unmistakable evidence of their presence throughout this system. In the next 1000 years autonomous probes will have arrived at the nearest stars.

Someone downthread claimed that this view is "comforting". Hogsnot. Knowing that you are the universe's mechanism for spreading the experiment of life is anything but comforting. What's comforting is belief (in the complete absence of any evidence to support it) that the landlord will take care of the damage we leave to our house and that there's nothing novel or unique about this place despite the fact that there are no other houses to be seen - anywhere.

"Surely", as in "surely we can't be the only planet with intelligent life on it" has an odd meaning. It generally is used to mean "this is a wild conjectural leap that I'm heavily invested in".

[joshcryer]

70. I think it's unlikely they would spread out.

It's more likely they would go to the core, and since we can't see the core, we don't know what's going on there. We're sort of in an isolated zone. Also, while they may want to find more info about the outer systems, sending intelligent probes would suffice, and they would be undetectable. So if we're not first in our galaxy it's possible our presence is known.

[Crunchy Frog]

51. I sort of see that as the last gasp

of the Ptolemaic, geocentric worldview. Not, of course, that the Earth is physically at the center of the Universe, but that it's the most specialest body in the Universe with humanity at the very pinnacle of creation.

I don't buy it.

[lumberjack_jeff]

54. There's only one piece of evidence on the topic.

The only footprints and alien artifacts on any extraterrestrial planets are the ones we left behind. Everything else is conjecture.

[Crunchy Frog]

61. True, but meaningless.

How many extraterrestrial planets have we actually explored? Human beings have set foot on exactly one other body in the Universe, and sent probes with limited capabilities to a handful of others, all in one single star system. This is in a galaxy with hundreds of billions of star systems, in a Universe with hundreds of billions of galaxies.

We can't even visualize extrasolar planets at this time, let alone do detailed explorations of them. There's vast quantities of data out there that we simply don't have the technology to access at this time. That doesn't mean it's not out there. That would be like definitively concluding the absence of microorganisms prior to the invention of microscopes because nobody's ever seen them.

Given the number of data points that we actually have, relative to everything that's out there, we can't conclude anything one way or another. It's all conjecture. IMO, the conjecture that we're the only life, or the only complex life, in the Universe, is Ptolemaic thinking.

It no doubt felt good to lots of people when we believed we were at the physical center of the Universe, and it no doubt feels good to some people now days to believe that we're the most specialest in the Universe. I don't personally buy it, though. With the paucity of data, though, people can believe pretty much whatever they want to believe.

[Duppers]

75. Me either.

Thx.

[joshcryer]

64. It should be coined the "rare intelligence hypothesis."

With "intelligence" conditioned on "intelligence capable of material science."

We will find life in the next decade or so. It will turn out to be extremely common. We will not find signals or evidence of intelligence, perhaps not in our lifetimes.

The dinosaurs ruled for 135 million years.

Intelligence is the fluke, not life.

[zappaman]

3. 6000 years ago!

Seems like yesterday Noah was building that ark!

[Mondavi]

6. Doubt it. We're a specieis totally unsuited for life on this planet...

[snooper2]

12. I know, we need those flappy thngs

flappy flappy fly fly FLY!!!

[NuclearDem]

14. There is a middle ground between anthropocentrism and misanthropy.

Plus the OP was about all life, not just Homo sapiens.

[Mondavi]

35. It is humans who have destroyed the planet ....

certainly other species have not as they cooperate with nature.
We destroy it.
How many animal species have we already destroyed?
And what of human illnesses we continue to create? Now 1 in every three Americans has cancer.

[TransitJohn]

41. The planet's destroyed?

How come I'm the last one to be told these things?

[Mondavi]

44. Possibly you haven't been paying attention?

Global Warming is the biggest threat to the future of human and animal-life and the planet itself.

[TransitJohn]

45. No, I think it was actually you engaging in hyperbole. eom

n/t

[Mondavi]

46. Is Global Warming and death of species "hyperbole"?

[TransitJohn]

47. No, but claiming Earth is already destroyed is eom

n/t

[Mondavi]

48. Global Warming is destruction of the planet...

We don't need earth to fall from the sky to understand the destruction.

[TransitJohn]

49. So you don't understand physics as well as geology.

Nice.
Just admit you misspoke and used the past tense. It's okay, really.

[Mondavi]

52. Rather you seem to not understand physics or geology....

We are past the time when we could have responded to Global Warming and that opportunity was when we were alerted almost 60 years ago. We have poisoned the planet, all animal life and ourselves.

[TransitJohn]

58. I'll just put my degrees in the dustbin, then.

I've been schooled by someone on the internet. Good job proselytizing. You should try to cultivate better tone, just my opinion.

[Mondavi]

63. If your education leads you to believe that Global Warming ...

is not the most serious threat we face, or that we don't have damage to the planet, animal life and human life, then that's probably what you should do.

Katrina, Fukushima, and serious weather related destruction across the planet and the most recent storms are yet the latest examples of not only the damage but the compounding damage from Global Warming.

[TransitJohn]

67. Now you're willfully misconstruing what I've said, this is about you saying the Earth is destroyed.

Stay on point.

[Mondavi]

69. Nonsense

You have no point and I'd suggest you try another poster who may not realize that.

[TransitJohn]

71. How do you continue posting from a destroyed Earth?

n/t

[dionysus]

57. a few million years after we're gone the planet will be good as new, don't sweat it. we just won't

be here any more

[TransitJohn]

59. You can't discuss real issues with people who have a belief that life or Earth are sacred

It clashes with their religion.

[oldhippie]

68. "... humans who have destroyed the planet ...." They have?

Hmmmmm. My part of Texas is still here. Where are you?

[Adrahil]

72. What does this have to do with the OP? NT

[Mondavi]

73. See

my post #6 and post #53 by another poster

[jeff47]

17. No, we are extremely well suited for life on African savannahs.

We're not well suited for life in lots of other climates. But that is exactly the same as every other species on the planet - each species is suited for the climate in which it evolved.

[Mondavi]

36. We cannot survive the extremes of Global Warming ....

Heatwaves kill us. So do flooding conditions. Do do winds at 100 mph.
Landslides and fires.

[jeff47]

37. So your complaint is that we are flammable and don't have gills.

Ooo-kay.

[Mondavi]

40. All "climate" has been and is being changed by Global Warming ...

and even desert climates are hotter than ever.

You are also ignoring that human activity has already destroyed life for thousands of species of animals on this planet. And we humans are also suffering the consequences of pollution and destruction of nature evident in Global Warming.

jeff47 quote --
No, we are extremely well suited for life on African savannahs.

We're not well suited for life in lots of other climates. But that is exactly the same as every other species on the planet - each species is suited for the climate in which it evolved.

[jeff47]

42. Except that isn't what you were talking about above.

Above, you were claiming that humans are not suited to any climate on this planet.

We are. And technology has let us live in additional climates. Climate change does not mean we are not suited for any climate on the planet - even in the worst-case scenarios, there will still be places on Earth where we can survive quite nicely with no technology. They're going to be further north and south than the African savannahs where we evolved.

[Mondavi]

43. You're misreading what I said ....

What I said was "humans are unsuited for life on this planet" and that human activity has destroyed nature and made the planet unlivable for humans and other species.
Exploitation of nature has rested in the hands of elites who have not cooperated with nature as animal life does -- i.e., we are "unsuited" for life on this planet as a species.

Much of our technology is based in war weapons and much of it even for alleged peace time use like nuclear reactors are dangerous to all life. We have Fukushima disaster threatening not only Japan but our own coasts directly. All nuclear reactors should be shut down.

Technology such as air-conditioning and heat have allowed us to live in comfort for a short period of time. Drop the atomic bomb, see temps rise and make air conditioning available to the masses as temperatures soar. However, all of this technology only creates more Global Warming as it it is based on burning fossil fuels.

You might also have noticed that our car air conditioners are unable to keep up with the extreme heat once the car has heated up.

Additionally, Global Warming has been bringing and will continue to bring disruptive storms which knock down power lines which are mainly above ground and year after year we see more and more citizens disconnected from heat or air conditioning, even lights for longer and longer periods of time. It's a further complication of elite/corporate greed and exploitation for profit which has pushed for transporting power across country to monopolize profits and which is becoming more and more obvious as Global Warming increases.

The few may survive for a short time, if that's the argument you want to make?

Reminds me of Dr. Strangelove arguments for surviving an all out atomic war. Always look on the bright side of life?

[defacto7]

53. I subscribe to the

"Humans more closely resemble a virus than and animal" scenario. Animals and non-human life add to the earth and only take what they need, then they die and add to the living by their death. Humans feed, and multiply, and never give back until finally killing its host. That's a virus.

[Mondavi]

56. Sadly, wholeheartedly agree with you.

[bemildred]

9. Occam's Razor says we are not special.

Intelligent life is likely to be much less common than life as such. Intelligence is expensive and evolution would not produce it except in certain environments with certain lifestyles. It takes a certain scale and complexity of environment to make intelligence a paying proposition. Of course, once you have it, other possibilities open up.

[Otelo]

10. I thought that meant "a second later"

It meant half a billion years. Is that "about as soon" as it could have possibly had occurred?

[NuclearDem]

13. Yep. Natural selection and what not.

[Arugula Latte]

15. Yes -- Statistically there must be a huge number of planets supporting advanced life

around the universe. We can't really grasp the concept of one billion, yet think about one hundred billion galaxies, and how many planets of differing conditions those galaxies must yield. Of those planets, a certain percentage will be the right make-up of substances and distance-from-star/s to support evolving life forms.

And that is why our Earth-centrism and sense of we-are-the-most-special-thing-in-the-universe is ridiculous, and why the make-believe of traditional religion is incredibly myopic, to say the least.

[jeff47]

16. There's another factor for those large hydrocarbons

Earth currently has an oxidizing atmosphere, thanks to all the photosynthetic life. So large, complex hydrocarbons will tend to break down over time when exposed to air.

But pre-life Earth had a reducing atmosphere. Large, complex hydrocarbons were not broken down by air.

[cthulu2016]

20. Excellent point. Yes.

[Iggo]

19. wRONG! gOD DID IT!

[JaneyVee]

23. .

[Junkdrawer]

24. My guess....

One of the biggest mysteries still outstanding in 21st century science is this: How did life originate from inanimate matter. With Darwinian evolution, we believe we have a handle on how primitive, replicating life evolved into more and more complex life forms, but, as far as I know, we have little idea how even the most primitive life forms originally developed.

Life on Earth is currently protein based with DNA and RNA nucleotides controlling the replication of cells. Proteins, in turn are comprised of amino acids and we do, thanks to the 1952 Miller-Urea experiment, have a pretty good idea how amino acids may have arisen on a planet with a carbon dioxide, nitrogen, hydrogen sulfide, and sulfur dioxide atmosphere. But here we seem to be stuck waiving our arms saying that somehow, given enough time, life must have spontaneously appeared – the Primordial Soup hypothesis. The problem is that even the most primitive self-replicating cell we know of is so incredibly complex, that spontaneous generation is beyond credulity.

As a lay person looking into the field of evolutionary biology, I see an enormous amount of effort trying to overcome the first step of the problem: exactly what sort of pre-life structures are capable of spontaneous generation? And this is an important question, but certainly not the only question. Other fundamental questions would include “How does Nature select between the different structures capable of spontaneous generation?” and “Why did Nature choose to combine these spontaneous generated structures into something like a cell capable of that Rube-Goldberg-like thing we call mitosis?”

In order to not get bogged down in the initial question of what sort of pre-life structures are capable of spontaneous generation, I will speak of Black Box processes. In engineering, especially electrical engineering, a Black Box is a system described solely in terms of its inputs and outputs - with the internal workings undetermined. In the rest of this paper the Black Box models will be exceptionally simple. This is by design so that we can get a flavor of the concepts involved. Later, we could add complexity to the models and, with computer simulations, see if the concepts identified sill hold.

Let’s begin with the problem of selection. How would nature select one pre-life process over another? Well, if we were talking about how Darwinian evolution would select one organism over another, we would look to see which organism is best able to gather and consume the scarce resources of a given environmental niche and then replicate. Since the main resource in the Primordial Soup scenario is the amino acids themselves, let’s consider a few thought experiments and see how far this takes us.

We begin with the simplest scenario I can think of: two Black Box processes, say BBA and BBB, both are able to join together the same three amino acids, but each produces unique proteins we’ll call ProteinA and ProteinB. We’ll also assume BBA joins the amino acids twice as fast as BBB, and that there is a finite amount of amino acids. Clearly, at the end of this experiment there will simply be twice as much ProteinA as ProteinB. However, if we further assume that both ProteinA and ProteinB naturally break down to their constituent amino acids at a rate slower than their formation, a more interesting result occurs. As the newly freed amino acids will form ProteinA twice as fast as ProteinB, given enough time, only ProteinA will exist in any quantity and only a trace amount of ProteinB will be found. Now both BBA and BBB still exist, but as far as impact on the environment, as measured by their eventual outputs, it’s as if BBB never existed. This may be how Nature selects between different pre-life processes.

In order to attack the next question(s), I have found that it was necessary to put some precision of language around the problem. Indeed, in the rest of this paper, I will offer some insights this more precise language has given me to date.

Let BB0 represent the set of all pre-life Black Box processes capable of spontaneously generating in a given environment containing only amino acids. Let’s notate each member of this set as BB0,M where M is an integer starting with 1. Let E0,M represent the number of BB0,M members that will spontaneously generate in a given volume over a given time. We’ll call this the Existential function for the BB0 set. A fractional number such as 0.5 will mean that it takes two time periods before a BB0,M member will appear.

Now, the next insight is that once we have BB0 processes occurring, the environment has changed. We now have primitive proteins as well as amino acids in the new environment. This will allow us to define the next set:

Let BB1 represent the set of all pre-life Black Box processes capable of spontaneously generating in a given environment containing amino acids and at least one of the primitive proteins generated by the BB0 set. The important thing to note here is that the E1,M existential functions will all contain a term that represents the number of one or more BB0 set members currently existent since, by the very definition of the set, BB1 members only spontaneously generate in the presence of one or more BB0 members.

We can now proceed and define BBN as the set of all pre-life Black Box processes capable of spontaneously generating in a given environment containing amino acids and the at least one of primitive proteins generated by BB(N-1) set. And we can refer to the increasing N subscript as “generations” with BB0 as the 0th generation, BB1 as the first generation, etc. etc.

Currently, without the introduction of additional concepts, all we have here is perhaps a more formal statement of the extremely low order of probably of the spontaneous generation of a complete cell capable of mitosis. But consider this thought experiment:

Imagine that there are a large number of BB0 processes possible, and they all have very, very small probabilities of forming. However, let’s posit that as we move to later generations, the probability of formation would increase were it not for the fact that they are dependant on the less likely formation of their predecessors. Now, what happens when a member of later generation starts to produce the protein(s) of the dependent BB0 set? Well, we would introduce a feedback loop, something like indirect replication. And, as there are in this example many BB0 processes possible, we may have many independent and, perhaps interlocking loops, each competing for the finite amino acid resource.

Another possibility in the preceding example is that, instead of replacing the protein of an earlier generation, the new protein creates a “helper” structure that simply increases the likelihood of an intermediate BB process spontaneously generating. This also could create or increase feedback loops. It would also help explain the creation of structures within current cells not directly related to protein generation.

It is important to note that, until now, we are talking about open solution processes. So, how and when do we move from open solution processes to replicating cells? I believe the answer may lie in enzymes. Suppose that one or more of the competing closed loop processes described above happens upon a protein that acts as an enzyme that breaks down a critical protein of a competing loop. This would certainly be a plus for the enzyme-generating loop as it both increases the amount of free amino acids while removing from competition the prey loop. But it would also setup a circumstance where the BB process which generates a protein that forms defensive semi permeable membranes (allowing amino acids in and keeping enzymes out) are more likely to remain in competition.. I would further guess that the development of cell walls is a late development as the walls that keep enzymes out may also keep out the proteins needed to form a cell capable of mitosis.

While I hope the ideas expressed in this paper shed some light on how inanimate matter may organize into something approximating life, it is, currently, a weak and insufficient light. I focus on protein generation and leave the incredible complexity of DNA/RNA in the shadows. But it is a beginning and I hope that it points in a direction that would eventually allow us to unravel this great mystery.

[dipsydoodle]

26. Unless..............

Vitamin B3 came to earth through asteroids

A new study has found that asteroids may have delivered vitamin B3 to Earth during early days of the planet. The findings of the study support the idea that extraterrestrial molecules played an important role in spawning life on earth.

"It is always difficult to put a value on the connection between meteorites and the origin of life; for example, earlier work has shown that vitamin B3 could have been produced non-biologically on ancient Earth, but it's possible that an added source of vitamin B3 could have been helpful," Karen Smith of Pennsylvania State University, said in a NASA news release. "Vitamin B3, also called nicotinic acid or niacin, is a precursor to NAD (nicotinamide adenine dinucleotide), which is essential to metabolism and likely very ancient in origin."

The researchers analyzed at samples of "eight different carbon-rich meteorites," the news release reported. These objects are called "CM-2 type carbonaceous chondrites".

http://www.delhidailynews.com/news/Vitamin-B3-came-to-earth-through-asteroids-1398010535/

[Warren DeMontague]

27. Space Supplements!

[Junkdrawer]

29. Yes. But where's the caffeine and taurine?

Something has to wake life up....

[chrisa]

55. Meteorite Vites!

[Junkdrawer]

28. Still need some sort of competition and selection....

leading to more and more complexity.

[dipsydoodle]

31. I only found that by accident just now when I posted it.

I was actually searching for origin of water of earth.

Comets, trans-Neptunian objects or water-rich meteoroids (protoplanets) from the outer reaches of the main asteroid belt colliding with the Earth may have brought water to the world's oceans. Measurements of the ratio of the hydrogen isotopes deuterium and protium point to asteroids, since similar percentage impurities in carbon-rich chondrites were found in oceanic water, whereas previous measurement of the isotopes' concentrations in comets and trans-Neptunian objects correspond only slightly to water on the Earth.

http://en.wikipedia.org/wiki/Origin_of_water_on_Earth

I assume such water may have contained bacteria.

[Junkdrawer]

32. Which, in turn, came from...

like kicking the problem to the next legislature...

Somewhere, somehow, goop has to turn to life.

[WhiteTara]

34. There is a Tibetan story

about a blind turtle who lives at the bottom of the sea. Once each 10,000 years, he rises to the surface. Our birth is so rare that it can be compared to the blind turtle who rises from the bottom sea and surfaces in the center of a floating ring.

I'd say our human lives are very rare and should be lived as consciously as possible.

[FarCenter]

38. Human lives are not rare; there are over 7,000,000,000 of them in existence currently

Standing 1 yard apart, they would cover a square about 50 miles on a side.

[WhiteTara]

39. Compare human life to ALL sentient life on this planet

which includes those that creep and crawl and fly and those that swim and those that run on 4 legs who live on and under the earth and in the trees and in the sea. Compared with the symbiont life forms that live on your body as you go about your daily existence, I'd say rare and with it comes some responsibility to become aware.

To live as a animal (who's only thoughts are of eating, mating, sleeping and defending) in the human form is a bit of an insult to what seems to be a walking, talking miracle.

But then, that's just me.

[IDemo]

60. Leaving aside the stereotypical UFO visitation

Because the idea that highly advanced civilizations will be inclined to pile into a glorified SUV for interstellar voyages, even if equipped with warp-speed capabilities, is a cartoonish scenario and probably the worst way to engage other ET's. To think that advanced beings will more often than not possess the spirit of wanderlust and the desire to build spaceships works well if you're into 50's sci-fi.

Sagan mentioned that for us to believe that other civilizations, statistically likely to be far more advanced, will rely on radio communication may be somewhat like listening for a bongo drum or looking for smoke signals in the stars. And as mentioned above, it would take an intentional and highly powerful signal to survive for any distance, not something that would result from an alien "I Love Lucy" broadcast. There may well be physics discoveries far down the road that will make SETI appear wishful thinking in retrospect. We may be in the midst of unimaginable communications but as unaware of it as ants on a Dish.

There is also the prospect that as civilizations become more technological, they tend to consume too much of the available energy and other resources before achieving the level of sophistication required to actually reach out and touch someone.

[Vashta Nerada]

62. Pfffft. Some loud and vocal people think some invisible sky fairy snapped his fingers and we were

here.



I like your explanation better. And The Doctor's:

[Hekate]

74. Go, Tardigrades! Creatures with more survivor potential than even cockroaches.

AFAICT, when the next mass extinction comes, Earth will still have the Tardigrades to start over with.

The things I've learned from Neil de Grasse Tyson.

[chervilant]

76. Bwahahahahahahahahaha!!!

...and if there were competing life modes... well, they were delicious.

Toooooo funny!

(Some of the responses herein above are hilarious, too!)