The idea that life on Earth originated elsewhere is not as far out as it seems
aeon.co
aeon.co
He had also imagined the concept of a "Cosmic mind" (Nous). If i understand well, for him, this "Cosmic mind" is not really an external metaphysical god, but more a physical part of the universe itself. A mind inside the universe, but isolated from the rest, and who try to organise everything else in the universe (including life).
Ofcourse there is a major difference between betting that "X is not different that all the Y's" and actually proving it :-), which is what makes this field of inquiry so fascinating.
The emergence of primitive proto-cells, then unicellular life, whereever it originated, seems quite easy to understand, and I'd agree with Stuart Kaufmann's "At home in the universe" suggestion that it appears more inevitable given a few environmental prerequisites than something requiring an extraordinary explanation. If interstellar RNA(?) did find it's way to earth, then it was likely competing with home-grown primitive cells, given what we know about early earth conditions and the inevitable rise of complexity.
The basic idea is that all it took for life/evolution to get started was a circular chain of chemical reactions (a primitive/proto-metabolism - consuming environment chemicals, and producing others) and some type of semi-permeable container (eventually to become a cell wall) such as a fatty bubble made out of hydrocarbons that can be produced in early-earth conditions. That's all evolution would have needed to get started - some froth on the seashore (or by the deep sea vent/whereever) "competing" with other flavors of froth for numerical supremacy.
The more interesting phases of evolution, which it seems are less inevitable (or perhaps I should say lower probability - but nonetheless inevitable given enough time) are things like the emergence of multi-cellular life, or what triggered the "Cambrian explosion" of variety to emerge.
Any aspect of the chemistry of a particular "colony" of proto-cells that played a role in helping create/preserve the chemical contents and structure of these proto-cells could be regarded as the earliest precursors of RNA/DNA. For example, if the localized chemistry generated self-serving catalysts, or transformed environmental chemicals into others that helped stabilize or produce the proto-cell bubble/container, then these become the beginnings of a colony that is self-defining and beginning to differentiate itself - starting to encode it's own structure.
For sure there's a long ways from these types of humble beginning to full blown RNA/DNA, but plenty of scope for the types of incremental improvement that would have driven evolution (better ability to utilize environmental chemicals and energy sources, better ability to survive environmental changes, better ability to replicate and disperse, etc, etc.).
It looks like there were bacteria on Earth just a few hundred million years after the planet formed a solid surface. On other hand next major steps in evolution - like eucariots and multi-cellurality took billions of years. Either early life evolution was extremely fast or life originated elsewhere and had much more time to evolve into bacteria and archea.
One panspermia hypothesis is life originated on Mars. It has a lot of iron, and iron catalysis a lot of the chemical reactions that probably made early life. Mars formed a solid surface about a billion years earlier than Earth. Also early on it had a magnetic field, that could protect a thicker athmosphere, that would allow for the existance of seas and oceans. So potentially life originated on Mars, took a billion years to evolve into bacteria/archea, which made the jorney to earth on pieces of rock, displaced by an asteroid impact (a lot of Marsian rocks fall down on Earth).
Not to mention, we have zero evidence that comets can really seed life and we also have absolutely no reason to believe that any place in the universe is better at spawning life than earth.
So I wonder, why is this idea so attractive?
More convoluted possibilities are less likely, but that doesn't render them impossible. You have to rule them out by evidence, not by unfounded bias.
Also, life on Earth started very fast, almost as soon as it was physically possible. That also seems quite unlikely.
We've got goldilocks conditions here on earth for creation of complex chemistries and emergence of life.
We've got all sorts of chemical elements, nice warm distance from the sun - lots of energy, but not too much to destroy things. Lots of liquid water, getting stirred up by a moon. A hot molten core providing both geothermal energy and a magnetic radiation shield. Plenty of lightening to initiate higher energy reactions...
Does it get an better ?
All those chemicals, getting mixed in water, stirred up by tides and thermal currents, heated up by the sun, are going to react ... no way to stop them.
In a few decades of trying a small number of labs experimenting with early earth type conditions have already been able to see organic chemicals created out of inorganic .. the building blocks of life, so imagine how common this would have been on early earth itself, with billions of micro environments chemically evolving 24x7 for millions of years ...
It's hard to say what we should regard as the beginnings of evolution, but this type of ever changing, ever complexifying stage of emerging organic chemistry on earth - essentialy an inevitability - could even be considered as the start.
If almost inevitable, then I'd also expect life to form readily in many other places too. Unless Earth was just very, very unusual in some way.
I would argue that this isn't precisely true. We know of some forms of relatively complex terrestrial life that can survive for indefinite (as far as we know) periods in vacuum - tardigrades are the most common example given.
For some other good candidates, I'd start with the list included the (failed) LIFE mission: https://en.wikipedia.org/wiki/Living_Interplanetary_Flight_E...
> What scientific problem would actually be solved by panspermia? Obviously, the product of two unlikely events is not more likely than one unlikely event by itself.
Panspermia is the belief that life is pervasive across the Universe. You don't have to believe that to believe that terrestrial life may not have originated here. From a statistically perspective, if we assume that life has arisen exactly once, it's no less likely that it arose on Mars as on Earth. Maybe some or all of the early history of life had already happened before the accretion of Earth. If that's the case, we'll likely never find direct evidence of it.
In short... I'd argue that panspermia doesn't "solve" any problems at all. If life is unique to Earth, we should be able to find evidence of its earliest forms. If it originated on Mars and was "seeded" here, then we should eventually find that evidence there. If it's universal, it still had to have originated _somewhere_; it's just going to be much more difficult to discover where.
To the best of my (lay) understanding, while we have a fair idea of how life might have began, we don't have very good evidence that it actually began on Earth.
What we do know:
* Earth is ~4.5b years old.
* The oldest fossils we know of are ~3.5b years old: https://news.wisc.edu/oldest-fossils-found-show-life-began-b...
* There exists evidence suggestive of life that is ~3.8b years old, in the form of what we believe to be precipitate from a oceanic hydrothermal vent that shows signatures of biological processes.
This means that in order for life to have arisen on Earth, it must have done so in the first ~1b years - because those oldest fossils mentioned above included multicellular life. To go from "primordial soup" to "multicellular microorganisms" is a pretty big leap, and we don't know the specifics.
Then there's the fact that _all_ known life either contains DNA or, in the case of RNA viruses, requires access to DNA-based life to reproduce. We don't know what came before that. Did primitive metabolism in come first, or genes (encoding structure in a durable and reproducible way)? Did they arise in tandem?
Either way, we are very confident that 1b years after the matter that we now know as Earth coalesced, there were multicellular organisms alive. Since all known life requires DNA, that means DNA was around at that point as well. That doesn't seem long enough to me, and apparently others share that intuition.
(edited for coherence)
A path like: (pre-TNA world ?) -> (TNA world ?) -> RNA world -> Ribonucleoprotein world -> Simple cells & viruses with DNA & RNA
https://en.wikipedia.org/wiki/RNA_world https://www.ncbi.nlm.nih.gov/books/NBK26876/ https://www.newscientist.com/article/dn21335-before-dna-befo...
It's one of the steeps before the cells than may have come from outer space because we did not find trace of them on earth. The other hypothesis is than they have disappear since then, because of later steeps in life history like the Great Oxidation Event.
Material is exchanged between planets, bacteria could survive such exchanges. So the possibility exists. People finding that uncomfortable is scientifically irrelevant.
Assuming transport just add another hypothesis.
EDIT: Also, if there was transport, they need to explain why we don't find life on the Moon. So the burden of explanation is more on that theory.
"Far from being rigid and fragile" - you can't make that claim without defining what 'fragile' WRT to which specific conditions. It's sloppy.
Only if we found a location that would provide simpler explanation for abiogenesis than on earth then panspermia as a theory would really be viable.
We'd probably know if there were a technologically advanced civilization around in the area immediate around Sol, at approximately the same time as today. That area isn't all that large due to the inverse square law; even if a species were actively trying to communicate with us via RF, it would be indistinguishable from the background quickly relative to astronomical distances.
We'd probably know (or know soon) if large-scale biological processes were happening near us, from the signatures of the chemicals that are the hallmarks of biology as we know it.
That we've found neither of those means we can't prove life exists elsewhere, but does _not_ prove that it doesn't.
That said, if abiogenesis were a common phenomenon, wouldn't we expect it to have arisen multiple times on Earth? The fact that we've not found any life that doesn't rely on DNA means is strong evidence of one of two things: either all life must have DNA, or life only arose on Earth once.
If life requires DNA... then where did DNA come from? We're back to square one.
If life only arose on Earth once, that's weak evidence that abiogenesis isn't common. By extension, it's weak evidence against panspermia.
(FTR I personally disfavour pasnspermia theory, I'm just addressing your argument's possible shortcoming).
again, "places" not "place". There may be billion other places so some will be more likely and some less so, by happenstance. And if it miraculously started in just one place and can spread, there you go.
They don't even have to be better, they can be just as good/bad, but that increases your chances by a billion because there are so many of them. One place just has to get lucky, that's all.
Again, I don't feel panspermia offers much, but there's the argument.
How it came on earth is not relevant in my opinion. Een if it was transported, it doesn't mean that life couldn't have appeared on its own on earth alone. Panspermia would be interesting if, for instance, we could show that Earth lacks an essential property for life to appear. But there is nothing in that direction. Panspermia raises more questions than it answers (where did life appear, when, is it everywhere...).
> How it came on earth is not relevant in my opinion
Then just why are you even commenting on a panspermia thread.
> Panspermia raises more questions than it answers
agreed
There is on the one hand the (still very poorly understood) "pre-life" domain which is presumably a condition that may exist in various diverse zones in many planetary systems.
On the other hand there is the (fairly well understood) science of stellar evolution, nucleosynthesis etc. that creates the conditions for "pre-life" and for possible "pollination".
Panspermia is not so much a concrete idea of "fully formed" life going from A to B but rather exploring what kind of exchanges of "life-forming" catalysts may have happened over the first billions of years.
Actually, just ignoring that possibility is what would be unscientific, as it would comprise unfounded bias.
Besides, the video considers life from earth having spread to other planets first, with the reverse a less likely possibility.
Too bad we're not aware of any RNA-based life that can reproduce without access to DNA.
Once was enough.
It existed long enough only to - after exhausting study - re-engineer its own formula according to conditions and laws of ethernity and choosed the best - small fractal twist of a carbon based spiral was the minimal requirement supporting all the casess of: in minimal conditions being emergent, viral and unstoppable. Eternal.
Life.. may be common in space, uncommon in time.
(AI, as we know it, is dead not inert; as we don't know it, may be part ot that fractal twist..)
Even “intelligence” doesn’t seem to be that uncommon, even here on earth.
Enough intelligence to look outside and leave a planet may be rarer, given that only one species has it on earth - the dinosaurs were around for longer than humans, but why didn’t they develop enough intelligence and capability to do what we did?
How can you be sure they didn’t?
Well, where we looked, we haven't found it yet, so "all over the place" seems to be an exaggeration. At least it's not on the Moon, and not in any of our landing places on Mars.
Well, if it is so easy to you, then why don't you just get your nobel price, by demonstrating making life from lifeless molecules?
My take is, before we cannot do that, we cannot dismiss anything. Life is literal a great mystical thing to us and if it is not to you, you can proof so by experiment.
Lots of species are intelligent - not just the mammal kingdom (dolphins, apes, elephants), but also birds (corvids) and even molluscs (octopus), but nothing else has shown any tendency to develop the sort of runaway intelligence (and corresponding brain development => biological demand) that humanity has.
Seems likely that the average intelligence of animals was quite a lot lower in the Mesozoic, and that while high intelligence is evolvable, it takes a long time to evolve - whereas isolated island species do evolve radically large or small body sizes over a few thousand generations, change their diet substantially, and some certainly become _less_ intelligent, there aren't any examples of an island species evolving significantly higher intelligence to occupy a new ecological niche.
There’s a joke in Hitchhikers Guide that says dolphins are the most intelligent species on earth, to which the response is how can that be, all they do is happily swim around all day…
… yes, exactly, they’re the most intelligent species on the planet.
Ah, but humans today are fully capable of guiding our own evolution toward whatever goal we desire as a group, regardless of "fitness".
Perhaps there is a threshold of intelligence that, once reached, allows the possibility of that species becoming more intelligent and capable over time.
"However, there is now direct evidence that some of the so-called chemical ‘building blocks’ of life – organic molecules – can be found in comets."
Also, it seems hard to imagine a better place for life to emerge than Earth.
I can't watch the video right now, but what are the theories of how life got onto meteors in the first place?
Yes. If life originated from panspermia, and right after the planet had cooled down, that would imply that there should be a more or less continuous bombardment of panspermic seeds from the universe. If so, we should be receiving these seeds also now, and we should then be able to detect them.
Actually, we are - precursors to stuff like RNA have been found in comets and meteorites [1].
[1] https://theconversation.com/did-comets-kick-start-life-on-ea...
All extant RNA-based organisms require host DNA to reproduce. I see no reason to believe that RNA came first.
This, I'm not at all sure of. The density of the bombardment may be very weak, and very small. A tiny speck of dust here and there, what is there to detect?
(One reason is there's a lot more of not-Earth than Earth in the universe, but it's all pretty inhospitable.)
Pretty interesting kind of life too - able to survive in outer space for inter-stellar travel durations, able to withstand the scorching heat of ripping through earths atmosphere, then able to escape from a chunk of rock to populate the planet. That's more than pan-sperm, that's super-sperm!