Expectation of extraterrestrial life built more on optimism than evidence, study finds

April 26, 2012 by Morgan Kelly, Princeton University

(Phys.org) -- Recent discoveries of planets similar to Earth in size and proximity to the planets' respective suns have sparked scientific and public excitement about the possibility of also finding Earth-like life on those worlds.

But Princeton University researchers have found that the that — from bacteria to sentient beings — has or will develop on other as on might be based more on optimism than scientific evidence.

Princeton astrophysical sciences professor Edwin Turner and David Spiegel, a former Princeton postdoctoral researcher, analyzed what is known about the likelihood of life on other planets in an effort to separate the facts from the mere expectation that life exists outside of Earth. The researchers used a Bayesian analysis — which weighs how much of a scientific conclusion stems from actual data and how much comes from the prior assumptions of the scientist — to determine the probability of extraterrestrial life once the influence of these presumptions is minimized.

Turner and Spiegel, who is now at the Institute for Advanced Study, reported in the Proceedings of the National Academy of Sciences that the idea that life has or could arise in an Earth-like environment has only a small amount of supporting evidence, most of it extrapolated from what is known about abiogenesis, or the emergence of life, on early Earth. Instead, their analysis showed that the expectations of life cropping up on exoplanets — those found outside Earth's solar system — are largely based on the assumption that it would or will happen under the same conditions that allowed life to flourish on this planet.

In fact, the researchers conclude, the current knowledge about life on other planets suggests that it's very possible that Earth is a cosmic aberration where life took shape unusually fast. If so, then the chances of the average terrestrial planet hosting life would be low.

"Fossil evidence suggests that life began very early in Earth's history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn't reveal much about the actual probability of life on other planets," Turner said.

"Information about that probability comes largely from the assumptions scientists have going in, and some of the most optimistic conclusions have been based almost entirely on those assumptions," he said.

Turner and Spiegel used Bayes' theorem to assign a sliding mathematical weight to the prior assumption that life exists on other planets. The "value" of that assumption was used to determine the probability of abiogenesis, in this case defined as the average number of times that life arises every billion years on an Earth-like planet. Turner and Spiegel found that as the influence of the assumption increased, the perceived likelihood of life existing also rose, even as the basic scientific data remained the same.

"If scientists start out assuming that the chances of life existing on another planet as it does on Earth are large, then their results will be presented in a way that supports that likelihood," Turner said. "Our work is not a judgment, but an analysis of existing data that suggests the debate about the existence of life on other planets is framed largely by the prior assumptions of the participants."

Joshua Winn, an associate professor of physics at the Massachusetts Institute of Technology, said that Turner and Spiegel cast convincing doubt on a prominent basis for expecting extraterrestrial life. Winn, who focuses his research on the properties of exoplanets, is familiar with the research but had no role in it.

"There is a commonly heard argument that life must be common or else it would not have arisen so quickly after the surface of the Earth cooled," Winn said. "This argument seems persuasive on its face, but Spiegel and Turner have shown it doesn't stand up to a rigorous statistical examination — with a sample of only one life-bearing planet, one cannot even get a ballpark estimate of the abundance of life in the universe.

"I also have thought that the relatively early emergence of life on Earth gave reasons to be optimistic about the search for life elsewhere," Winn said. "Now I'm not so sure, though I think scientists should still search for life on other planets to the extent we can."

Promising planetary finds

Deep-space satellites and telescope projects have recently identified various planets that resemble Earth in their size and composition, and are within their star's habitable zone, the optimal distance for having liquid water.

Of particular excitement have been the discoveries of NASA's Kepler Space Telescope, a satellite built to find Earth-like planets around other stars. In December 2011, NASA announced the first observation of Kepler-22b, a planet 600 light years from Earth and the first found within the habitable zone of a Sun-like star. Weeks later, NASA reported Keplers-20e and -20f, the first Earth-sized planets found orbiting a Sun-like star. In April 2012, NASA astronomers predicted that the success of Kepler could mean that an "alien Earth" could be found by 2014 — and on it could dwell similar life.

While these observations tend to stoke the expectation of finding Earth-like life, they do not actually provide evidence that it does or does not exist, Spiegel explained. Instead, these planets have our knowledge of life on Earth projected onto them, he said.

Yet, when what is known about life on Earth is taken away, there is no accurate sense of how probable abiogenesis is on any given planet, Spiegel said. It was this "prior ignorance," or lack of expectations, that he and Turner wanted to account for in their analysis, he said.

"When we use a mathematical prior that truly represents prior ignorance, the data of early life on Earth becomes ambiguous," Spiegel said.

"Our analysis suggests that abiogenesis could be a rather rapid and probable process for other worlds, but it also cannot rule out at high confidence that abiogenesis is a rare, improbable event," Spiegel said. "We really have no idea, even to within orders of magnitude, how probable abiogenesis is, and we show that no evidence exists to substantially change that."

Considering the source

Spiegel and Turner also propose that once this planet's history is considered, the emergence of life on Earth might be so distinct that it is a poor barometer of how it occurred elsewhere, regardless of the likelihood that such life exists.

In a philosophical turn, they suggest that because humans are the ones wondering about the emergence of life, it is possible that we must be on a planet where life began early in order to reach a point so soon after the planet's formation 4.5 billion years ago where we could wonder about it.

Thus, Spiegel and Turner explored how the probability of exoplanetary abiogenesis would change if it turns out that evolution requires, as it did on Earth, roughly 3.5 billion years for life to develop from its most basic form to complex organisms capable of pondering existence. If that were the case, then the 4.5 billion-year-old Earth clearly had a head start. A planet of similar age where life did not begin until several billion years after the planet formed would have only basic life forms at this point.

"Dinosaurs and horseshoe crabs, which were around 200 million years ago, presumably did not consider the probability of abiogenesis. So, we would have to find ourselves on a planet with early abiogenesis to reach this point, irrespective of how probable this process actually is," Spiegel said. "This evolutionary timescale limits our ability to make strong inferences about how probable abiogenesis is."

Turner added, "It could easily be that life came about on Earth one way, but came about on other planets in other ways, if it came about at all. The best way to find out, of course, is to look. But I don't think we'll know by debating the process of how life came about on Earth."

Again, said Winn of MIT, Spiegel and Turner offer a unique consideration for scientists exploring the possibility of life outside of Earth.

"I had never thought about the subtlety that we as a species could never have 'found' ourselves on a planet with a late emergence of life if evolution takes a long time to produce sentience, as it probably does," Winn said.

"With that in mind," he said, "it seems reasonable to say that scientists cannot draw any strong conclusion about life on other planets based on the early emergence of life on Earth."

This research was published Jan. 10 in the Proceedings of the National Academy of Sciences and was supported by grants from NASA, the National Science Foundation and the Keck Fellowship, as well as a World Premier International Research Center Initiative grant from the Japanese Ministry of Education, Culture, Sports, Science and Technology to the University of Tokyo.

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THENAMEIS_____
3.6 / 5 (5) Apr 26, 2012
Sure there indeed is hype especially in the media about Extraterrestrial life, but from an scientifically theoretical perspective, there is a very high possibility for life, other than Earth. It's more like an indirect evidence, but soon, hopefully we through find intelligent. When that day does occur, it would be a very profound moment for humanity. I find it boring to think that humans are the only intelligent, and frankly, such a claim is illogical.
Deadbolt
3 / 5 (2) Apr 26, 2012
Sample of one bias, but at least the universe might be infinite.
pauljpease
4.7 / 5 (9) Apr 26, 2012
What's more likely, that out of all the visible Universe, life arose only one time, and that life survived for 3.5 billion years and evolved to the complexity of sentient organisms, but it NEVER arose AT ALL, ANYWHERE ELSE, EVER... or that there's probably some other life out there? I think that the fact that we KNOW life can emerge even once suggests that it probably has emerged more than once. Earth, as astronomers are beginning to show us, isn't that special. Regarding the research discussed in this article, what a waste of brain cells, by the way. Their main conclusion is, "we just don't know", which obviously implies we have no reason to EXPECT to find life out there, but as they admit, we have no reason not to expect it either, we really just don't have enough data.
tk1
2 / 5 (3) Apr 26, 2012
Why is it illogical? Until such a time as another "intelligent" life form is known, then we are the norm, anything else is spectulation.
dogbert
3 / 5 (6) Apr 26, 2012
Excellent article.

As I have noted many times, there is a strong tendency for media and even scientists to plainly state that life is inevitable and widespread in the universe despite zero knowledge of any life anywhere except in this solar system.

There is no logical way to assign a positive probability when there is zero data.

The universe may be teaming with life -- and I hope it is. But there is no reason to suspect that it is.
StarGazer2011
2.7 / 5 (3) Apr 26, 2012
Excellent article.

As I have noted many times, there is a strong tendency for media and even scientists to plainly state that life is inevitable and widespread in the universe despite zero knowledge of any life anywhere except in this solar system.

There is no logical way to assign a positive probability when there is zero data.

The universe may be teaming with life -- and I hope it is. But there is no reason to suspect that it is.


There is equally no reason to suspect it isnt.
Lack of evidence is not evidence for a lack. Like many questions the only correct response is 'We dont know'.
I think Paulipease's response is good, we know life exists on Earth, so why would we not expect it to exist elsewhere there are similar conditions?
Remember it was only 20 years ago that we could have the same argument about the existence of extrasolar planets.
And how can these guys say with a straight face that life arose 'early' on Earth when they have zero data points for comparison?
Terriva
1 / 5 (5) Apr 26, 2012
Well fucking duh. That's why it's called an expectation. If it were based on evidence it wouldn't be an expectation it would just be reality. Why We Have So Much "Duh" Science? Apparently it's the byproduct of the huge overemployment in mainstream science and a waste of public resources.
typicalguy
3.8 / 5 (5) Apr 26, 2012
I suspect other life exists in the solar system. Why you ask? Because impacts on earth send rocks into space with bacteria on/in them that can go into survival mode. Then those rocks fall on mars, europa, other locations that it can thrive, and many that it can't. I think it's safe to assume we will find life in the solar system and it uses DNA like us. Life outside the solar system would be easier to discover with very powerful telescopes that can actually visually see the surface of exoplanets. Let's face it, we are very unlikely to find radio signals from them for numerous obvious reasons.
borc
3.7 / 5 (3) Apr 26, 2012
"So, we would have to find ourselves on a planet with early abiogenesis to reach this point, irrespective of how probable this process actually is,"
one of the articles assumptions is that all planets are the same age. their theory is that life out there would be unlikely to be as advanced as us because it started so 'early' here, but what if it started comparatively late on another planet that is a few billion years later. The statistical probability of life not arising on any rock ever is so excedingly rare when you take into account moons planets, and even deep space planets that might harbor bacterial life near geothermal vents. the number of potential bodies is so excedingly large... probability dictates a high chance of it existing.
johnnyringo
4 / 5 (4) Apr 26, 2012
I suspect the authors are not statisticians, because it's the sheer, unbelievably gargantuan number of stars and planets which exist in the Universe that guarantees alien life forms. Such phenomenal numbers of possible "homes" for life dictates that we are not alone.
simplicio
5 / 5 (4) Apr 26, 2012
"Our analysis suggests that abiogenesis could be a rather rapid and probable process for other worlds, but it also cannot rule out at high confidence that abiogenesis is a rare, improbable event," Spiegel said.

So what is the use of this paper? It says maybe yes, maybe no. We already know that. This is just waffling.
javjav
5 / 5 (5) Apr 26, 2012
Why is this so important? To me, the important thing is that the probability for abiogenesis is not zero, as it happened here, so it is something that can happen naturally. From that point, how big is this probability is a secondary thing. It does not matter too much if they are one, tens, or billions of planets with live. I agree that this probability value is an interesting question, but not the fundamental question which is already answered: Live exists.
ziphead
1 / 5 (2) Apr 26, 2012
We do not know what we do not know; is it really so bloody hard to admit? What Turner and Spiegel or whoever may think is irrelevant until we do know more.

In the meantime, plenty of boring Earthly problems for scientists to solve. So, get cracking.
dogbert
1.8 / 5 (5) Apr 27, 2012
The universe is built from the same stuff that we are, so the chemistry here is the same as the chemistry elsewhere.

So to say that there is zero data is incorrect.


OK, VD, so point to the system outside this solar system that has been found to contain life. Just one. If you cannot point to a system which has been found to contain life, than there is no reason to claim that any system other than this system has life. Zero evidence for life outside this solar system is just that -- we have no knowledge of any solar system except this one which has life.
javjav
4.2 / 5 (5) Apr 27, 2012
Zero evidence for life outside this solar system is just that -

I do not agree. This is not zero data. But it depends on how do you formulate the question:

We already have an approximate idea (which is improving each day) about how many "habitable" planets are in our galaxy. Then, the main question remaining is this:

"What is the probability of live appearing in an "habitable" planet?"

What we know is that this probability is greather than zero, as at least one habitable planet has live (ours). This is much more knowledge than "zero data".
Birger
2 / 5 (2) Apr 27, 2012
There is probably plenty of lichen and bacterial slime out there... but no ET. We may be the first technological civilisation in the Milky Way, or even the Local Group.
Isaacsname
5 / 5 (1) Apr 27, 2012
I'm pretty certain Life exists out there.

Somewhere out around Orion's belt ;)
antialias_physorg
5 / 5 (4) Apr 27, 2012
but the knowledge about life on Earth simply doesn't reveal much about the actual probability of life on other planets

with a sample of only one life-bearing planet, one cannot even get a ballpark estimate of the abundance of life in the universe.

FINALLY someone with an understanding in statistics put it in a paper. One datapoint does not allow ANY conclusions (other than: "yes: life is possible").

Neither does this allow for the conclusion that life is sparse, BTW. It just means: we haven't got a clue how prevalent life is out there.

That will only change if we:
a) find life somewhere else
OR
b) find out that abiogenesis happened several times on Earth

That said: Searching for such life is certainly an inspiring endeavour. Nothing wrong with getting people motivated.
Torbjorn_Larsson_OM
not rated yet Apr 27, 2012
This is the Rare Earth hypothesis, again supported by bayesian methods. Reading the free pre-review paper in arxiv, the authors have to assume that that abiogenesis can't be a generic process but is widely different on different planets. If you assume Earth isn't representative, Earth isn't representative.

Instead we can do usual hypothesis testing. Abiogenesis, having prebiotic chemistry evolve into protobiotic cellular life, could be a repeated process of attempts over time and locales. In the simplest stochastic model this belongs to the family of Poisson processes.

Such processes stacks their probability mass early, due to their exponential distribution. A homogeneous Poisson process has P(T > t) = e^(- L*t).

This is a testable model. [to be continued]
Torbjorn_Larsson_OM
not rated yet Apr 27, 2012
To simplify we use a normed distribution where observation time t = 1. Since this is a one-sided interval from t = 0, we want to have a set of distributions with at least 0.99 of the probability mass within the interval.

The probability mass is expressed by the cdf (cumulative distribution function). Inserting into the Poisson cdf, we get F(t,L) = 1 - exp(-t*L)>= 0.99 -> t*L > 4.6.

Now t = 1 corresponds to L ~ 5. That means the normed waiting time T ~ 0.2. With actual time t* ~ 5 Gy we get actual waiting time T* ~ 1 Gy.

With current understanding we have putative observations of life from ~ 3.8 - 3.5 Gy ago.* Earth aggregated ~ 4.5 Gy ago, which means the interval gets close to the required 1 Gy.
antialias_physorg
5 / 5 (1) Apr 27, 2012
This is the Rare Earth hypothesis, again supported by bayesian methods.

No it is not.

Quote from the article
with a sample of only one life-bearing planet, one cannot even get a ballpark estimate of the abundance of life in the universe.

What they are saying is the data (more specifically the lack thereof) allow for no conclusions either way.

}If you assume Earth isn't representative, Earth isn't representative.

They are assuming no such thing. They are saying that they don't know whether Earth is representative (or has anything to do with the likelyhood of having life on it in the first place) - and that there is no statistical basis for making even a guess either way.
Torbjorn_Larsson_OM
not rated yet Apr 27, 2012
[@ Dogbert, antalias: There is not "zero" data or a statistical problem with using 'one' data point, nor are all the models using one data point.

We have a lot of data suggesting similar chemical evolution happen all over our system and, observed by spectroscopic means, all over the universe. I noted above how such a model is testable with one data point, weak as that observation is.

This is because we can use a stochastic process model, where the parameters comes out classical. You would of course like to have more data in the test, but that is a different concern. As an analogy, a collided car looks wrecked whether it was one collision or many.

The paper describes models were _the mere possibility_ of repeated abiogenesis attempts are used in a similar fashion for a Las Vegas model of how to bet (for easy abiogenesis or not).
Torbjorn_Larsson_OM
not rated yet Apr 27, 2012
@ antalias: The comment field is short, and you haven't read the paper. I was refering to this in the pre-review paper:

"Between these limiting times, we posit that there is a certain probability per unit time () of life developing."

"If Mars and Earth have different s and life never arose on Mars, then the likelihood of Mars' (case i) is simply taken from Eq. (2), ... If Mars and Earth share a single and life did arise on Mars, then the likelihood of Mars' (case ii) is the joint probability of our data on Earth and of life arising on Mars. ... For case (ii ), we see that, should future researchers find that life arose independently on Mars, this would dramatically reduce the posterior probability of very low relative to our current inferences."

The case (i) comes out of their bayesian model. The (ii) is what I use above in a non-bayesian model.

"They are saying that they don't know whether Earth is representative". Yes: assume Earth isn't representative, it isn't.
antialias_physorg
5 / 5 (4) Apr 27, 2012
There is not "zero" data or a statistical problem with using 'one' data point, nor are all the models using one data point.
There is not zero data but one datapoint delivers zero information

Shannon information:
http://en.wikiped...n_theory

Example: I use a random number generator (of which you know no particulars how it works - like we don't know how abiogenesis worked) - and I tell you the resultis 5.778
That is one datapoint.
Try to analyze as you may: It tells you nothing about the likelyhood of that number coming up again.

similar chemical evolution happen all over our system

Evolution says nothing about (abio)genesis. That's no part of it whatsoever (a fact which many religious people confuse when they attack evolution because they think it precludes a creator. There are many reasons to think a creator isn't part of the bargain - but the theory of evolution isn't one of them)

There is also no such thing as 'chemical evolution', BTW
Possibilus
not rated yet Apr 27, 2012
The premise that the tendency to believe that ET life exists is biased by our example...Earth, in the absence of other examples is not so. If our most basic scientific proofs, principles, observations have some degree of validity (physics, astronomy and the life sciences)...and if we accept observations of the universe so far indicate that there are patterns... elemental hydrogen and other elements are common throughout the universe, and that these elements, under the effects of radiation, gravity, and all other forces, coalesce into gases, stars, planets, and other objects, and if Earth formed from these same elements and forces where life became and evolved this is not based on optimism or faith, it is based on observation, understanding, and yes a theoretical or intuitive belief but it is not biased and without a sound basis of reasoning.
antialias_physorg
5 / 5 (3) Apr 28, 2012

Yet the universal nature of chemistry and physics and the existence of life on this planet provides reasonable assurances that life exists on other planets.

Again, no. That's not how statistics works. That's how we WANT things to work, but no scientific process supports this kind of conclusion.

Currently the only real answer is: we don't know.

Anything else (uniqueness OR ubiquitousness of life - or anything in between) is wishful thinking.
Lurker2358
1 / 5 (1) Apr 29, 2012
I suspect other life exists in the solar system. Why you ask? Because impacts on earth send rocks into space with bacteria on/in them that can go into survival mode. Then those rocks fall on mars, europa, other locations that it can thrive, and many that it can't. I think it's safe to assume we will find life in the solar system and it uses DNA like us.


Bacteria would not survive in space, simply because the lack of pressure would cause the water in it's membranes to boil away until it explodes.

Additionally, in the outer solar system, the temperatures are so cold that most organic molecular structures as we know them would not be stable. Most of the things we are familiar with in terms of life structures will freeze solid and shatter at the temperatures of Europa, which means it would be unimaginably unlikely for life to be ejected from Earth, land on the Europa moon, and somehow survive the journey.

Even Mars is a huge, huge stretch beyond any known Earth Extremophile.
Lurker2358
1 / 5 (1) Apr 29, 2012
You're not understanding the scale of an impact that would be required to eject a piece of life-bearing rock back into outer space at escape velocity.

The rock has to be big enough not to burn up on it's way back out of the atmosphere and again at the other planet, which means the EJECTED rock needs to be a minimum of like 10m diameter ball.

You're also not understanding the insane conditions this life would need to survive during that impact, during the ejection back through the atmosphere, during the space journey, during the re-entry at the other object, and then during the second impact on the other objects surface.

The Baringer Crater event is NOT large enough to do this.

Not only that, but the rock has to "get lucky" and land on Mars or Europa in a trillion to one head-on collision, since if it has Earth escape velocity it automatically has Mars and Europa escape velocity.
Lurker2358
1 / 5 (1) Apr 29, 2012
We would have a hard time keeping an extremophile bacteria alive on the surface of Europa, even in an designed experiment with a petri dish with a lamp, a heater, and a nutrient bath.

Some people just have the weirdest ideas that something could just get ejected up there and somehow survive. so ignorant.

I mean damn, the scale of the required EJECTED rock, just to even get the first condition right, is actually nearly as large as the Tunguska object.

So you want to take a freakin guess how big an impact and explosion it would take to eject that back into space at escape velocity, because that's how big the object needs to be in order to not burn up completely on the way back out...

In fact, collisions that large actually cause nuclear explosions, which complicates things even further for the potential "panspermia" life form...

So it has to survive:

initial impact
secondary nuclear explosion
burning up on exit of atmosphere
cold of space
burning up on re-entry
impact
environment
Smashin_Z_1885
1 / 5 (5) Apr 30, 2012
The truth of the matter is that any chance of any life (as we define 'life') existing anywhere else in the known universe is effectively zero. This can be easily calculated, and has been many times, by leading mathematicians utilizing all known data. The simple fact of the matter is that there are literally trillions upon trillions of conditions that must be absolutely correct in order for life as we know it, to exist anywhere. It can also be easily calculated, the ranges or variations within specific systems which are required for life to exist, and these ranges are exceedingly small. Do your research, and study this topic for yourself before making false assumptions that just because we exist, that surely others must also exist somewhere else. There exists no logical reason why such a condition such as that should exist. Example: The Earth is incredibly beautiful and full of life, therefore, other "earths" must also exist. There is no scientific basis for such an assumption.
Deathclock
4 / 5 (4) Apr 30, 2012
As with God, the null hypothesis is lack of existence until evidence suggests otherwise. It really comes down to whether or not you think there is evidence of life on another world... I don't think there is any evidence for that.

If I had to guess I would say there is probably other life out there, but right now that is irrational to believe that to be the case.

Note: I do not believe there is other life out there, I just said that if you force me to take a side I would say that it is more likely than not.
Deathclock
4.2 / 5 (5) Apr 30, 2012
The truth of the matter is that any chance of any life existing anywhere else in the known universe is effectively zero. This can be easily calculated, and has been many times, by leading mathematicians utilizing all known data. The simple fact of the matter is that there are literally trillions upon trillions of conditions that must be absolutely correct in order for life as we know it, to exist anywhere. It can also be easily calculated, the ranges or variations within specific systems which are required for life to exist, and these ranges are exceedingly small.


This is all wrong... life survives on this planet in every extreme condition imaginable. Life exists in pure sulfuric acid, life exists in extremely radioactive material, life exists in magma and volcanic vents at the bottom of the ocean at 600 degrees Celsius... Life can survive prolonged exposure to interstellar space...

Life is extremely robust.
LariAnn
2.5 / 5 (2) Apr 30, 2012
A major assumption made in this article is that "abiogenesis" (aka spontaneous generation) is how life arose on this planet. "We don't know" is the best answer when religion is not involved - no one has observed abiogenesis taking place here or anywhere, so it cannot and has not been studied scientifically. The fact that life exists here is not proof that abiogenesis was how it arose here. Not knowing how life actually arose here, we cannot come up with anything but speculation about how life might arise on any other planet.
Deathclock
3.7 / 5 (3) Apr 30, 2012
Abiogenesis (which is NOT spontaneous generation) on this planet or somewhere else is guaranteed.

Life came to exist somewhere... we know that for a fact. Whether it happened on another planet and was delivered to Earth on an asteroid or comet or whether it occurred here, you can say for sure that it happened. Kind of stupid to pretend otherwise.
Deathclock
5 / 5 (5) May 01, 2012
Abiogenesis (which is NOT spontaneous generation) on this planet or somewhere else is guaranteed.


That is the logical fallacy of begging the question. It has never been observed that life begins from non-life.


There are only two possibilities, either life has always existed, or life came into existence. Don't be retarded.

We only observe life coming from existing life.


we also only observe the bones of dinosaurs, so by your logic dinosaurs never existed, only their bones did.

So based on the available observations, the beginning of life is from other life is the logical conclusion.


That's not a conclusion you idiot... life coming from other life is obvious and gets us nowhere.

So to maintain that life must come from non-life is irrational, and based on blind faith.


Yeah and according to you it is irrational and based on blind faith to think dinosaurs ever existed when all we can observe is their bones.
Mastoras
not rated yet May 16, 2012
The conditions of the primordial Earth (composition of the atmosphere, existence of the ocean, temperature, expected storms and lightnings) all have been well determined. The creation of aminoacids in these conditions has been demonstrated experimentaly. As far as I am aware, the remaining problem is to show the appearance of the first cell.

All discussions for life in the universe were clearly mentioning the trilions upon trilions of planets and the few billion years of time. And mainly: giving values to the factors in the Fermi equation (percentage of stars having planets, percentage of planets with a long existence, etc.), was a clearly mentioned step.

So, expecting that, on statistical grounds, abiogenesis must have happened again many times, it is, I think, a well founded conclusion.

Saying that we expected life on exoplanets simply because abiogenesis happened here early, is a misrepresentation. I find the research reported here very unconvicing.
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