[HN Gopher] Why extraterrestrial life may not seem alien
___________________________________________________________________
Why extraterrestrial life may not seem alien
Author : NotSwift
Score : 148 points
Date : 2021-08-02 15:26 UTC (7 hours ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| petters wrote:
| > there are certain things we can still say about them with
| reasonable certainty. Topping the list: They evolved.
|
| This is far from certain. They can be designed by someone who was
| designed by someone who evolved, for example. The evolved life
| forms may be extinct for millions of years.
|
| Even simple life forms on other planets may be designed, e.g. for
| someones (analogous to) amusement.
| petters wrote:
| Follow-up: Earth is at a tipping point right now. So far life
| has been governed by evolution. But within a short time
| (<=10,000 years, say) it will likely be possible to simulate a
| human brain quite cheaply. Then things will get weird quite
| quickly. See Robin Hanson's book about "Ems."
|
| For these reasons I think we can expect that aliens really will
| be quite alien to us.
| ajoy wrote:
| I think we have to consider the possibility (most likely), that
| the advanced versions of these lifeforms are much further along
| the evolutionary tree than we are. They might have evolved like
| us, but continued evolving and now look nothing like us.
| armchairhacker wrote:
| I always wondered, what if there is "life" that exists going
| backwards in time? Like, consider our laws of physics, except
| entropy is decreasing. Imagine a "life form" which interacts with
| the world, grows, replicates, and evolves backwards in time. So
| to us, it would seem to start out as a massive colony, then
| shrink and devolve. To them, we would seem the same.
|
| How would you even detect them? Communicate with them? You can't
| just send a message, because they would instantaneously "forget"
| it (since they process information backwards), and vice versa. I
| doubt we could consider them "alive" at all.
|
| Also, their laws of physics would be so different. Imagine shards
| of glass, at rest on our world, suddenly start joining together
| into a glass bottle. That's what life looks like to them.
|
| Yet everything else is the same. They live in the same, the same
| laws of physics. They could even exist on our planet. Except we
| exist in a state of increasing entropy, and they exist in a state
| of decreasing entropy.
| prof-dr-ir wrote:
| An intelligent being in a 'state' of decreasing entropy seems a
| little difficult to imagine.
|
| Much more realistic, IMO, would be a civilization that was made
| entirely of dark matter. Perhaps they might be able to infer
| our existence if we built some insanely powerful particle
| accelerator (and vice versa). If not then we would presumable
| only be able to communicate through gravitational effects...
| DesiLurker wrote:
| its possible but since we are in very very very early (think
| 10E9 out of 10E100) stages of our universe I'd imagine the
| reverse part would happen towards the end of our current time,
| assuming the time reversed processes have same endpoints as
| time fwd processes.
| 4e530344963049 wrote:
| Reduced by 73% Reduced page load from original size of 5.11 MB to
| 1.36 MB.
|
| https://trimread.org/articles/82
| TheDudeMan wrote:
| It seems likely that a civilization would experience a robot
| apocalypse/revolution prior to achieving interstellar travel.
| rendall wrote:
| There's an entire genre of these kinds of books that extrapolate
| generalities (life throughout the Universe) from a single data
| point (life on Earth), but the truth is, that's not even an
| educated guess.
|
| We do not know if our evolutionary pressures are universal. We do
| not know if the evolutionary solutions developed here are
| appropriate even on other Earth-like planets, much less
| everywhere. Sensitive dependence on initial conditions could lead
| to radically different planetary environments, necessitating
| radically different _mechanical_ solutions to survival, some
| (many, most?) of which we will never have even imagined.
|
| What creatures would form under an intense magnetic field? In
| methane? In close orbit around a dim star? In a hot cloud nebula?
| Could we even recognize them as alive, much less intelligent?
| Definitely not if we're looking for bats and monkeys and
| octopuses
|
| No, I think the whole genre of "life is much the same everywhere"
| suffers from a profound lack of imagination
| DrBazza wrote:
| This is a theorised list of biochemistry that might support
| life
| https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...
| rendall wrote:
| Thanks. That's great
| Koshkin wrote:
| Nitpick: "bio" = "life"
| NotSwift wrote:
| Physics and chemistry impose some serious constraints on all
| life forms. On earth we have convergent evolution, independent
| groups of species independently develop similar solutions for a
| specific problem. Life on other planets will have similar
| problems, e.g. reproduction, locomotion and perception of its
| environment, and its solutions will probably be similar to the
| ones we have on earth.
| kenjackson wrote:
| But changes in the environment and initial starting point can
| result in very different approaches. For example land
| mammals, reptiles and fish are quite different from each
| other. Because they've "always been here" we don't appreciate
| how different they are. Imagine if we had no fish and then
| found a planet with water that had fish in it -- that would
| seem absolutely shocking to see animals that could breathe
| underwater.
| alkonaut wrote:
| Of course the environment will determine life forms. What the
| article says is that if there is a gaseous atmosphere, for
| example, then selection will reward animals that are able to
| move through it. That means for organisms that are heavier than
| the surrounding atmosphere - most likely - wings. For liquid
| environments, there probably aren't that many locomotion
| techniques that are both effective _and_ missing on earth,
| meaning when we see something swimming in water on a different
| planet it'll look like a jellyfish, octopus, fish, worm, clam,
| bacteria, shrimp, horse... or one of the other hundreds of ways
| of swimming
| rendall wrote:
| Once we move outside Earth-like conditions, we should be
| decreasingly confident about our speculations, not more
| confident. What are the chemical and physical conditions of a
| hydrocarbon lake at 5g, -180C, 1 kilotesla and 100
| atmospheres? Can we really be confident that "whale" is the
| best mechanical solution for moving around there? Can we
| really be confident that "moving around" would even be the
| best survival strategy? I think not.
| alkonaut wrote:
| Indeed earth evolutionary processes require earth like
| conditions. But here I mentioned swim in _water_ which is a
| pretty strict constraint on temp vs pressure.
|
| That said even in any other fluid I _doubt_ we'll ever look
| at an organism and say "it swims like ... <blank>" because
| there wasn't an earth organism that swims anything like it.
| Of course that means comparing to _every_ method of
| swimming locomotion on earth which is a staggering
| diversity from the microscopic up to whales.
|
| Unless other forces are involved (e.g electromagnetism
| isn't used for locomotion on earth to my knowledge) and the
| fluid is incompressible like water, then I'm (armchair)
| guessing "to swim" doesn't have _that_ many evolvable
| solutions, regardless of pressure /temperature and the
| specific chemistry.
| yourenotsmart wrote:
| The example of convergence between fish and dolphins, birds and
| insects, the infamous "why does everything evolve into crabs"
| study and so on should tell us that while we should be open for
| radically different forms of life, the most likely outcomes
| will look like something we've seen here on Earth.
|
| I'm personally expecting something like 80% humanoids and 20%
| exotic forms. Maybe I'm primed incorrectly by cheesy soap
| operas and sci-fi TV shows, but I think they're not far off
| (even if for unrelated reasons like SFX/VFX budget and
| character empathy).
| rendall wrote:
| ... on planets. That have a precise similarity to Earth.
| Sure, I can provisionally accept that.
| dogorman wrote:
| > _convergence between fish and dolphins_
|
| The convergence between dolphins and ichthyosaurs is even
| more remarkable. Ichthyosaurs were marine reptiles; air
| breathing tetrapods that, like dolphins, had ancestors that
| walked on land but eventually returned to the sea to kick
| fish ass.
|
| https://en.wikipedia.org/wiki/Ichthyosaur#/media/File:Ichthy.
| ..
| spywaregorilla wrote:
| Given how rare humanoid shape is on Earth, it doesn't seem
| especially sure that humanoids will be dominant among even
| intelligent life.
| dtech wrote:
| Arms+hands and a head with a similar face though.
|
| A head is pretty universal because eyes are so important
| and a feeding hole near your sensory organs is a massive
| advantage.
|
| Having hands seems almost a pre-requisite to become truly
| intelligent and tool-using.
| titzer wrote:
| Octopi have all the things you mentioned (except hands).
| Their eyes are even better than human eyes. No one would
| describe them as "humanoid".
| JoeAltmaier wrote:
| Hm. We have what, a dozen or more on Earth? Apes, monkeys,
| homo etc. Plus dozens of dinosaurs that stood on 2 legs. It
| seems pretty common.
| ajuc wrote:
| a dozen out of millions of species is not "pretty common"
| JoeAltmaier wrote:
| Many convergent evolution paths led to the same similar
| form, in time. That was the point. If the environmental
| pressures are similar, the forms may be similar.
| asah wrote:
| 100.0% of spacefaring earth creatures are bipedal /s
| mike_hock wrote:
| Sure, organisms that already share a massive amount of
| commonalities can diverge and then converge again.
|
| What about the branches that happened early on? We
| essentially have only two lineages of macroscopic organisms
| that are actually fundamentally different: Plants and
| animals.
|
| I would expect any kind of macroscopic extraterrestrial life
| to be at least as distinct from Terran plant and animal life
| as they are from each other.
| yourenotsmart wrote:
| DNA is extremely flexible, there's no macroscopic form or
| shape it can't take, as various insects camouflaging
| themselves as sticks and leaves and what not shows.
|
| So the idea we'll see some vastly different concepts with
| different starting blocks is possibly unfounded.
|
| Alien life might be very different at low level depending
| on their environment, but in terms of macroshapes, things
| like the formation of a head with eyes and mouth, upper and
| lower limbs, bilateral symmetry and so on will repeat over
| and over.
|
| We'll see (in another life probably).
| mike_hock wrote:
| Yeah, but so what? The geometric shape isn't very
| interesting. The insect camouflaging itself as a leaf
| still functions as an insect. It doesn't perform
| photosynthesis.
|
| Considering that we have a whole class of lifeforms that
| have nothing like a head with eyes and mouth or limbs,
| the idea that this would evolve independently more likely
| than something completely different, is also possibly
| unfounded.
| harperlee wrote:
| Having two eyes, as a simple example, is arguably the
| cheapest way to perceive 3d at things-may-want-to-eat-me
| distance: just two points that enable triangulation.
| Similar constraints reduce the configuration space a lot.
| It still remains huge, but I don't think someone that
| believes about certain convergence to be necessarily
| naive.
| spywaregorilla wrote:
| > DNA is extremely flexible, there's no macroscopic form
| or shape it can't take, as various insects camouflaging
| themselves as sticks and leaves and what not shows.
|
| That feels like a really bold claim given the evidence.
| ncmncm wrote:
| Let me know when you spot an animal that drives around on
| wheels.
| pvaldes wrote:
| rotifers
| dtech wrote:
| Physically you could have wheeled animals, but wheels
| just won't evolve. They are perfect for somewhat smooth
| surfaces where you want to travel in a somewhat straight
| line. Organisms just cannot confine themselves to that
| and survive.
|
| Unless we find a planet composed entirely of solid smooth
| rock we won't find wheeled animals.
| jhgb wrote:
| How would wheels get fed with nutrition? Would they have
| tiny mouths?
| depressedpanda wrote:
| > We essentially have only two lineages of macroscopic
| organisms that are actually fundamentally different: Plants
| and animals.
|
| That's not true, we also have fungi as a macroscopic
| lineage.
|
| Or maybe you put them in the plant group? If so, that's a
| mistake, as they are more closely related to animals than
| they are to plants.
| uh_uh wrote:
| I think it's fine to lump fungi together with plants for
| the spirit of this discussion. The distinction between
| plants and fungi are made on the basis of metabolism but
| in this thread people are clearly talking about external
| behaviours observable with the naked eye.
| aaronblohowiak wrote:
| Weir's latest book goes into this. (Ex: Audible hearing is
| based on the distribution of frequencies generated when solid
| bodies collide or rub.)
|
| On the other hand, If life is that which can use an energy
| differential to create more order within it (an entropy pump)
| then sure there are likely forms of "life" out there that we'd
| have a harder time imagining (that perhaps operate at physical
| scales and timescales beyond us -- thinking nebulae)
| rendall wrote:
| > _Audible hearing is based on the distribution of
| frequencies generated when solid bodies collide or rub._
|
| ... in Earth-like conditions, and useful in Earth-like
| conditions. Vibration of denser or rarified gasses could
| require other solutions to exploit, if it 's possible at all
|
| > _If life is that which can use an energy differential to
| create more order within it (an entropy pump)_
|
| Now that's the ticket! Under this definition, I suspect most
| life in the Universe is _not_ carbon based, but far more
| exotic (to us)
| Koshkin wrote:
| > _What creatures would form_
|
| On the one hand, the conditions under which some lifeforms are
| thriving here on Earth are already pretty extreme.
|
| On the other hand, indeed, we may not yet be in a position to
| be able to imagine, realistically, all that we would
| (eventually) agree to call a lifeform. (Life built from phonon
| "particles" in a planet-size crystal, anyone?) Sure, there may
| be constraints, such as life, in a meaningful sense, may only
| be realizable based on polymers, in which case the conditions
| must be such that they allow polymerization of simple
| substances to take place.
| titzer wrote:
| > On the one hand, the conditions under which some lifeforms
| are thriving here on Earth are already pretty extreme.
|
| Not really. They are all within +/-5km of the planet surface,
| live under 1g of gravity, as a rule, are _not_ exposed to
| X-rays, gamma rays, cosmic rays, strong magnetic fields or
| nuclear radiation, or extreme temperatures. There 's nowhere
| on Earth that receives more than about average solar
| radiation or gets much above 100C where life survives.
|
| Life generally has access to ample oxygen, though a few
| anaerobic organisms exist. They're all DNA-based, have access
| to ample amino acids, aren't bathed in thousands of
| completely toxic chemicals, have liquid water (and not, e.g.
| liquid methane). The list goes on and on.
|
| Yeah, there are a few extremophiles, but they are by far the
| minority, and are clearly adapted incrementally from other
| organisms that evolved in non-extremophile environments. In
| essence, there's a large reservoir of easy-pickins living
| that generates biodiversity to cross over into extremophile
| environments.
|
| Now imagine 5x the gravity, 100-1000x the solar irradiance,
| the lack of magnetic field (and thus direct exposure to solar
| winds), no atmosphere, or atmosphere entirely composed of a
| toxic gas, extreme exposure to X-rays, etc. The universe is
| full of many places where Earth life, even extremophiles,
| would have no chance of survival. And such places don't have
| reservoirs of biodiversity from which to adapt to these
| conditions. They're just dead.
| collaborative wrote:
| Didnt they find life where no one was expecting it to be?
| (Dark bottom of the sea, under intense pressure and
| surviving on vents). Deep sea creatures also look really
| alien. Might be a clue of the "weirdness" we might find out
| there
| rendall wrote:
| > _They 're just dead._
|
| We have exactly one example of an environment that nurtures
| life. It does _not_ logically follow hence that it is the
| _only_ environment where life can thrive (unless we choose
| to define life as that which thrives in an Earth-like
| environment)
|
| I do agree that probably most of the Universe is hostile,
| not only to Earth-like life, but to life of any definition.
| But we cannot be certain. We have never visited nor sent a
| probe to a 5g planet "100-1000x the solar irradiance, the
| lack of magnetic field (and thus direct exposure to solar
| winds), no atmosphere, or atmosphere entirely composed of a
| toxic gas, extreme exposure to X-rays".
| titzer wrote:
| I'm actually in agreement with you. Those places I
| mentioned probably do not have DNA and amino-acid based
| life that looks anything like Earth, particularly because
| those environments eviscerate the delicate chemistry
| necessary for that particular system to work. So life
| would look totally different.
|
| I'm more of the "Boltzmann Brain" persuasion. Life might
| take the form of electromagnetic waves or metallic
| structures that are respirating, self-replicating,
| information-processing things. In my more paranoid days,
| I think the internet is alive, as it is kind of like a
| life-form growing our the substrate of our collective
| digital actions.
| causi wrote:
| Agreed. At a bare minimum, human thought patterns have to be
| rare. At some point we're either going to murder ourselves or
| create a Von Neumann machine capable of interstellar flight.
| After that humans or human-derived machines will fill the
| universe. Since that obviously hasn't happened with alien
| machines, the aliens are either not alive or totally unlike us.
| idiotsecant wrote:
| There is a book Accelerando by Charles Stross that talks
| about why neither case might be true - he shows a scenario
| where life ultimately transforms its host system into a
| matrioshka brain. At that point distance from the cloud is
| reduction in bandwidth to the parts of yourself that exist in
| that cloud- if the matrioshka brain can simulate billions of
| planets and leaving it makes you incredibly stupid by your
| normal standards why do it?
| nootropicat wrote:
| >why do it
|
| Because if you don't, someone who does is going to invade
| for energy and resources. Therefore, refusing to expand is
| a slow form of suicide, unless you can be somehow certain
| there's no entity like that in the potentially accessible
| space.
|
| At some point growth in any star system is going to be
| finished - energy extraction near maximum, no free matter
| left to convert into computronium. After that, only two
| solutions remain: stagnation (death) or expansion. Assuming
| no instant communication (not just FTL - instant), the
| bandwidth argument only means it makes more sense to haul
| energy and computronium from the rest of the accessible
| space into one point.
|
| We may very well already see it somewhere far away,
| thinking it's "natural" rather than a construct. I think
| under current knowledge the most likely prediction is
| something resembling a sphere (minimizing distances between
| points) that utilizes black hole power plants, feeding them
| matter from stars and nebulae.
|
| From the outside, it would look like a giant void with
| nothing in the center. Maybe there's something like that in
| the center of the Bootes void?
| causi wrote:
| Accelerando is a great book even if his writing style is a
| little dry. The mass of one planet being able to simulate
| billions of planets is only possible if the simulation is
| rather poor. You can't create a perfect simulation like
| that any more than you can perfectly simulate seven atoms
| using three atoms. Computation is never going to be more
| efficient than physics.
|
| _why do it?_
|
| Everyone doesn't have to do it. Just one person out of
| billions does. Think of the strange and perverse collection
| of behaviors we observe in a population of a few hundred
| million people online and speaking English. Expand that to
| billions of hyperintelligent minds and _somebody_ is going
| to want to colonize the universe.
| rendall wrote:
| > _At a bare minimum, human thought patterns have to be
| rare._
|
| Definitely. In fact, I think they are almost certainly unique
| in our entire local galaxy cluster, and we will never find
| anything even close.
|
| We could very well find something interesting, enlightening,
| sophisticated or using what we might be able to squint and
| call _technology_ , but I suspect we will never find an
| _alien civilization_ intentionally broadcasting for example
| the fibonacci sequence or prime numbers so that we can learn
| to exchange culture and communicate ideas.
| cryptoz wrote:
| I don't agree that human thought patterns have to be rare, or
| your other assumptions. The only safe bet in this discussion
| I think, is, we don't know anything for sure.
|
| > At some point we're either going to murder ourselves or
| create a Von Neumann machine capable of interstellar flight.
|
| There are many, many possibilities for human futures that are
| between those two and not do extreme. It is absolutely
| possible we survive millions of years without interstellar
| travel or self destruction.
|
| > Since that obviously hasn't happened with alien machines
|
| I also think it is not so obvious that this hasn't happened
| or isn't happening with alien machines. It certainly could be
| and we would not know either way. A la 2001: A Space Odyssey,
| perhaps in fact we are a product of alien machines
| themselves.
| guyomes wrote:
| > Could we even recognize them as alive, much less intelligent?
|
| If we focus on recognizable features, we may look for organisms
| with self-replication skills (a feature of living organisms)
| and prediction skills (a feature of intelligent organisms).
|
| On the intelligence aspect, the skill to predict the future in
| general, and imminent threats in particular is useful for
| structured organisms less resistant than rocks to survive. On
| that matter I wonder, do unicellular organisms on earth have
| prediction skills?
|
| What also helped those fragile structures to continue existing
| along rocks after a long time might be their ability to
| replicate themselves before being destroyed. Reproductive
| skills might actually be the first interesting feature to look
| for in extraterrestrial organized structures.
| theyellowkid wrote:
| >There's an entire genre of these kinds of books that
| extrapolate generalities (life throughout the Universe) from a
| single data point (life on Earth), but the truth is, that's not
| even an educated guess.
|
| Hey, whatever sells a pop science book pounded out over a long
| weekend.
|
| It's funny how sure everyone was about slowing expansion of the
| universe and the idea of close rocky planets/distant Jupiters,
| but only lucky guessers are remembered.
|
| It could simply be that patterns for lifeforms on Earth were
| set so long ago that everything sort of rhymes. Veer that path
| at the beginning and you end up with a significantly different
| answer.
| rendall wrote:
| That's so in alignment with my thinking I'd like to buy you a
| beer
| Koshkin wrote:
| > _drink it and forget it all!_
|
| https://www.goodreads.com/quotes/78268-a-poet-once-said-
| the-...
| rendall wrote:
| Koshkin, theyellowkid, I, and whoever else thinks aliens
| are probably profoundly weird: drinking and coming up
| with increasingly outlandish ideas for aliens. Now that
| sounds like a party.
| theyellowkid wrote:
| When considering deeper questions, I always think of this
| short story.
|
| https://www.gutenberg.org/files/33854/33854-h/33854-h.htm
| JoeAltmaier wrote:
| Nah. Think of fish - and the assertion "There's no such thing
| as a fish." That refers to the similar evolution of many
| branches of life that ended up "looking like a fish" but are
| otherwise unrelated.
|
| They had a common ancestor of a coral-like sea squirt (If I
| remember right). That looked nothing like a fish.
| autokad wrote:
| I completely disagree. I think the 'life can look like
| anything' (lets call them LCLLAs) train of thought suffers from
| a lack of understanding of constraint satisfaction.
|
| Think about how some LCLLAS talked about how silicon life is
| probably a thing. First off, it it were, given Earth's crust is
| mostly silicon and its the most habitual place ever discovered,
| it would have evolved here. but it didnt. It turns out silicon
| is just too ridged, and to get life going you need all sorts of
| chemical properties that just aren't congruent to life.
|
| We are carbon / oxygen organisms for a chemical reason. despite
| the availability of other resources, other forms of lifeforms
| didn't develop for a reason. maybe other forms of life does
| exist in some methane ocean on Saturn like planets, but its not
| going to be very complex, and definitely not intelligent life
| building space ships.
| rendall wrote:
| "Other forms of life didn't develop for a reason" isn't that
| convincing of an argument. We are somewhat knowledgeable
| about what chemical and physical processes can occur between,
| -100c to 1500C under 1atm or so, +-100 nanoteslas, in a
| timescale of under a human attention span. Beyond that, we
| become increasingly clueless.
|
| We have only a single very specific data point. That, and the
| human tendency to opine confidently about that which we
| cannot know.
| hackeraccount wrote:
| What's the path-dependency-ness of life? Like, once you have
| carbon based life to what degree does it preclude silicon
| based life from evolving? How often does a feature evolve sui
| generis when the nich that the feature exploits is already
| filled? Clearly it happens sometimes so if you've got a good
| enough angle you can step into something that's seemingly
| already covered.
|
| For all that after several billion years it's just carbon
| based life forms in these parts. You'd think that there must
| be some area where silicon based life would provide an
| advantage. Unless it's a case that carbon based life is an
| overwhelmingly superior product but on some hypothetical
| world it's simply filled with silicon and there's virtually
| zero carbon.
| vimacs2 wrote:
| I disagree with this assessment of silicon based life. While
| it is true that Earth's crust is mostly silicon, it's also at
| a temperature that would make metabolic processes using
| silicon very difficult until you get down to the mantle.
|
| It could be that silicon based life is in fact constrained by
| temperature and can only arise in planets where the mean
| temperature is in the thousands. This could in fact mean that
| we do have a parallel silicon based biosphere underneath our
| feet. There is obviously no evidence for this whatsoever but
| then again, there is no reason to assume that the occasional
| leakage in the form of volcanic eruptions would leave any
| trace that we could use to deduce that these samples were
| once living entities.
| hackeraccount wrote:
| Doesn't it intuitively seem like the life by definition
| would evolve out of any particular niche - say 1,000
| Kilometers under the surface - to other areas?
|
| I'm at best doubtful about life on Mars because I find it
| hard to imagine some form of life that occupies a small
| part of Mars i.e. it's only in the parts we haven't seen. I
| tend to think if there's any life on Mars it'll find a way
| to deal with the conditions on all of Mars. By the same
| token if there's any silicon based life then it'll pop up
| in places that we can find as well as those we can't. Maybe
| it does best in places we can't but surely there would be
| some oddball silicon based creature that would beat the
| odds.
|
| The macro example would be the extinction of the South
| American marsupials when the North and South American land
| masses merged. All the placental animals in North America
| went south and all the marsupials in South America went
| extinct. Except for Opossums which for whatever weird
| reasons not only survived but went into North America.
| drdeca wrote:
| What do you mean by "by definition" in that first
| sentence?
|
| Like, if it failed to do so, it would fail the definition
| of life? I don't think anyone defines life that way, and
| I don't think it would be a good definition (would I even
| count as alive under such a definition? It seems like
| no.)
| rendall wrote:
| > _Doesn 't it intuitively seem like the life by
| definition would evolve out of any particular niche - say
| 1,000 Kilometers under the surface - to other areas?_
|
| Other areas that are similar, sure. But if you're
| asserting that we can be confident there are no
| subterranean mantle-creatures because we don't see any
| wandering about out here, I don't think it's a good
| argument, for the same reason we can't go _down there
| ourselves_ and look
| rendall wrote:
| If mantle-creatures were to exist, they would have a far,
| far greater volume of living space to expand into than we
| surface-dwellers do. Maybe they just haven't gotten
| around to us yet, for the same reason we don't have any
| large cities in the antarctic.
| vimacs2 wrote:
| No because if this was true, then we would see carbon
| based life do the exact same process in reverse. However,
| there is a limit to adaptability, particularly through
| the dumb and highly stochastic process of natural
| selection.
|
| We have no evidence of a void ecology in near earth orbit
| or of life persisting close to the Moho barrier - where
| the crust meets the mantle. There are hard limitations to
| the encroachment of life that only technology or
| radically different chemistry can circumvent.
|
| The same hard barriers might also mean that life on Mars
| is largely constrained to those few underground liquid
| water lakes that we have recently found evidence for.
| Keep in mind that even the most barren deserts on Earth
| have several orders of magnitude more water present in
| the air than on Mars.
| gambiting wrote:
| I'm just always surprised how can we be so certain? Even here
| on Earth, for millions of years, life was literally nothing
| more than single cell organisms - also definitely "not
| intelligent life building space ships". And it would be very
| hard to see how could it possibly evolve into such, seeing as
| the atmosphere was full of incredibly toxic oxygen.
|
| The thing is, life has almost infinite time to evolve out of
| these various elements. The fact that it didn't evolve here
| on Earth means absolutely nothing, seeing as Earth alone has
| billions of years left where such life could arise, and there
| are literally countless planets everywhere in the universe
| where the random dice of evolution roll every second.
| depressedpanda wrote:
| > seeing as Earth alone has billions of years left where
| such life could arise,
|
| In case you didn't know, Earth has about one billion years
| of water left.
|
| https://www.sciencedaily.com/releases/2013/12/131216142310.
| h...
| gambiting wrote:
| I do know that, but it's few billion before the earth is
| consumed by the expanding sun. Without surface water the
| planet is still there.
| Retric wrote:
| It's a question of physics not just chemistry. Deuterium
| for example is similar to hydrogen chemically so while
| those differences are slightly toxic to us it's easy to
| assume a planet similar to earth with an abundance of
| deuterium and a lack of hydrogen would evolve life forms
| with the opposite preferences.
|
| Except the ratio of hydrogen to deuterium is a function of
| astronomy and more specifically fusion. No naturally formed
| planet is going to end up with that imbalance. Which means
| no natural deuterium based life forms. So while some alien
| civilization create deuterium life, it's not going to be
| part of natural ecosystems.
|
| And so it goes for most possible interesting edge cases.
| Dependency on rare elements like Neptunium means any
| competitors without that dependency have huge advantages.
| gambiting wrote:
| Of course. But there are planets with abundance of
| silicon(including ours). There are planets with abundance
| of methane and even here we have lifeforms which can
| consume it. I'm just pointing out that as long as silicon
| based life is possible, then given the near infinite
| amount of time the universe can spend evolving such life,
| it will surely exist.
| [deleted]
| Retric wrote:
| Sort of, it depends on how common various forms of proto
| life are. If their very rare and the first one to happen
| wins then you might expect silicon life of some form to
| be out there.
|
| On the other hand if proto life is extremely common then
| silicon proto life might always be out competed by more
| efficient alternatives. For example the fact Silicon
| dioxide is a solid where carbon dioxide is a gas is a
| major advantage or using carbon.
| ncmncm wrote:
| The silicides would meanwhile say that the gaseous nature
| of CO2 makes carbon useless as a basis for life, and even
| go so far as to offer a plausible reason.
| Retric wrote:
| Sorry, no. CO2 being gaseous is a major availability and
| energy advantage. For example you can't get plankton
| equivalents as dissolved silicon is parts per trillion at
| the oceans surface.
|
| Hybrids are a different story, but I doubt that's what
| anyone is talking about by silicon based life forms.
| ncmncm wrote:
| CO2 (or SiO2) is only one of the possible outputs, or
| inputs, of metabolism. Even on Earth its primacy came
| very, very late.
|
| You don't get to constrain alien life to your
| preconceptions. Even some Earth life secretes SiO2. Using
| carbon for some things would not invalidate its Si-
| basedness any more than diatoms have given up carbon-
| basedness.
|
| Silicon's near absence from our favored solvent, like
| iron's, is a product of toxic levels of biogenic
| atmospheric oxygen. Our early oceans were saturated with
| iron products, and are now starved of them. There is no
| reason to assume oxygen would be their favored oxidant.
| rendall wrote:
| It's an interesting point.
| autokad wrote:
| I would say, get your head out of your edge cases. Before I
| go on, I hope you understand no one is saying its not
| physically possible, and that it absolutely does not exist
| anywhere in the multiverse, just that if we come across
| other life, it will most likely be similar to our own.
|
| by definition, the most probable form of life in the
| universe is the 1 we are observing. you only need math and
| probability to figure that out. We also have observational
| evidence. As far as we can tell, there is no other life in
| our solar system. We have 8 other planets and many moons
| that have failed at creating life in any form - that's
| literally hundreds of billions of years of failed attempts
| at life.
|
| you can't just pick an element and think its going to work.
| you need ALL the elements, ALL the states of matter, and
| the right ratios and amounts of elements to work. Even if
| you get that lined up, expecting complex life to form under
| enough pressure to create diamonds in thousands of degrees
| centigrade also puts the probability of complex life off
| the table.
|
| I don't known who this is hard to understand. in the
| simplest example as the article states, if you want to fly,
| there are things that necessitate something that will fly,
| such as wings. no wings, no fly. sure its POSSIBLE you can
| fly without wings, but UNLIKELY. given that we have
| multiple lineages of evolution taking different paths that
| end up with the same solution is evidence of that.
| d0mine wrote:
| You won't see any wings on a hot air balloon. If you
| think it is not common, look at the fish in the ocean.
| autokad wrote:
| now you have de-evolved the conversation by trying to
| change the definition of fly to swim. if you are going to
| do that, there is no point in continuing the discussion.
| Furthermore, you are confusing buoyancy with flight.
| rendall wrote:
| > _get your head out of your edge cases_
|
| The Earth is the edge case, is the point we're making.
| All of the conclusions and deductions about what life
| must be like elsewhere that use Earth as their implicit
| foundation are going to be _overfit to the data_ , so to
| speak. _Organisms on Earth converge to similar forms:
| dolphins and fish, bats and birds, for instance, so the
| form is useful on Earth_ is a valid observation.
| _Therefore, we can expect to see these forms throughout
| the Universe_ is a quite a jump.
| user-the-name wrote:
| > The Earth is the edge case
|
| You do not know that. All available evidence points to
| the opposite: We have no knowledge, not even a hint, of
| any other physical process that could sustain life than
| that of Earth's carbon-based chemistry.
|
| The idea that life could take a myriad of different forms
| is beautiful, but it is pure fantasy, based on no
| evidence at all.
| gambiting wrote:
| >>We have 8 other planets and many moons that have failed
| at creating life in any form - that's literally hundreds
| of billions of years of failed attempts at life.
|
| Again, how can you be so certain of it? Life could have
| existed in some form on Mars or Venus or even Mercury
| millions if not billions of years ago, only to be
| extinguished by the changing conditions in the solar
| system and ground to absolute dust by time. Maybe not
| advanced space faring civilization, but life could have
| existed in those places and you simply don't know.
|
| >> you only need math and probability to figure that out.
|
| Yes, and maths and probability are telling me something
| very opposite to what you are saying. That if you are
| observing a solar system like ours(forget the entire
| universe for a second) for a ~100 years out of billions
| of its existance, then sorry, but you don't know anything
| about it, certainly not if it harboured life in the past
| or not, not to a degree that you seem to be certain of.
| amelius wrote:
| > First off, it it were, given Earth's crust is mostly
| silicon and its the most habitual place ever discovered, it
| would have evolved here. but it didnt.
|
| Just give it a few more decades ...
| yawaworht1978 wrote:
| Well, stage one to silicone life could be computer chips.
| Then for a transition period, the shell could be metallic
| followed by integration of the human mind to that almost
| indestructible body shell. Something like the bad guy
| terminator 2. But step one could be computer chips. Human
| designed and made rather than by strict definition of natural
| selection.
| torginus wrote:
| If we assume for a second that silicon life is a thing, would
| it be reasonable to think that it would be utterly alien?
| Probably it's chemical composition would be entirely
| different, but would it be unreasonable, that it could evolve
| eye, muscle, bone etc. analogs just like us, and the end
| result would be not entirely unfamiliar to our earthly eyes?
| The article talked about wings being one of the few viable
| modes of flight, and Richard Dawkins has made a lecture about
| eyes having evolved independently multiple time here on earth
| (like in, as the article states, mammals or octopi).
| mimixco wrote:
| I read somewhere that the most likely "alien" visitor is a
| bacterium, virus, or other organism that rode here on a meteor
| fragment. That achieves interstellar travel without the need or
| intelligence or intent. It was also the subject of the terrific
| movie _The Andromeda Strain_.
| birdyrooster wrote:
| Also for me was the scariest movie I saw growing up even
| against Child's Play, Halloween, Friday 13th.
| mimixco wrote:
| Yes! Still scary. The realism of it is alarming to this day.
| ncmncm wrote:
| It has no realism at all. Why would an organism with no
| experience of Earth environment outcompete life evolved to
| it?
| outworlder wrote:
| Why not? We see invasive species outcompeting native
| species all the time.
| ncmncm wrote:
| They all come from an extremely similar environment, and
| typically eat or infest very similar prey/hosts.
| jnurmine wrote:
| Perhaps it evolved on a planet with an Earth-like, but
| much harsher, environment.
|
| To draw an analogy from fiction, what would happen if one
| sent Giger's Alien in all its glory, razor tail and all,
| to compete in an entry-level boxing match? The Alien has
| no rules, has acid for blood, tongue-crushes the skull of
| the referee, and so on.
| Andrew_nenakhov wrote:
| Soviet writer/philosopher Ivan Yefremov (probably, the most
| influential soviet Sci-fi writer) argued rather convincingly,
| that humanss have ideal body size and layout for intelligent
| beings, and that extraterrestrial life would probably look
| somewhat similar.
| genesis126 wrote:
| God: "I thought so too"
| TedDoesntTalk wrote:
| The article mentions that we have 4 limbs only because the
| creature that left the sea had 4 fins. It could easily have
| been 6 or 8. He makes it seem as though 4 was just plain
| random.
| Andrew_nenakhov wrote:
| Having more limbs is less efficient biomechanically - the
| creature would need a larger heart to pump blood through al
| organs, that requires more energy, so such creature would
| need more food.
|
| Now, it is known that creatures can lose limbs through
| evolution, but never gain them, so it is likely that multi-
| legged species would gradually lose extra limbs over time.
| goatlover wrote:
| Octopuses mange to do okay. And they seem alien enough for
| a related species. Cephalopods serve as a good counter to
| the article.
| Joker_vD wrote:
| > creatures can lose limbs through evolution, but never
| gain them
|
| Wait, so where did the limbs come from anyway, if they
| could not be gained?
| Andrew_nenakhov wrote:
| Early creatures had mady different body plans. We have 4
| (all vertebrates), 6 (insects), 8 (arachnids) and
| multilegged creatures (millipedes), as well as legless
| creatures like snakes (who had 4 legs before they lost
| them).
|
| It seems that vertebrates have certain period when this
| layout was 'cast in stone' [1]
|
| [1]:
| https://biology.stackexchange.com/posts/21793/revisions
| benfarahmand wrote:
| Reading your comment made me wonder why we have even
| numbers of limbs for different body plans. I realized
| it's due to bilateral symmetry for most organisms must
| some how be advantageous to asymmetric body plans, but
| I'm unsure how symmetry is advantageous. What are the
| evolutionary pressures selecting against asymmetric body
| plans?
| Andrew_nenakhov wrote:
| I'm not really a biologist, but I think this has
| something to do with the balance: when you move in some
| direction, it would be extremely disadvantageous to have
| one side significantly heavier than another.
|
| Take two runners, give one a 15 kg weight in one hand,
| and give another 15 kg weights in both hands (30 kg
| total). I think the runner with weights in both hands
| would run faster than the one with one weight.
|
| Thus, moving species evolve to be bilaterally symmetric.
|
| If the organism has no need to move in certain direction,
| it doesn't really have bilateral symmetry, like trees or
| bushes (though big trees generally tend to have their
| center of mass close to their vertical axis).
| jnurmine wrote:
| One thing I've found fascinating is how the outside
| appearance of a human body repeats the number 5; there are 5
| things sticking out from a center mass (2 legs, 2 arms and
| the head). Each foot has 5 toes, each hand has 5 fingers. And
| in the head are 5 outward-facing holes: 2 eye sockets, one
| nose/mouth hole and 2 ears.
| ncmncm wrote:
| Seeing how alien ctenophores seem, despite having evolved here,
| the thesis seems shaky.
|
| Aliens will _probably_ eat, breathe, see, smell, and hear, but
| might do it in ways that would fail to qualify under definitions
| we can write based on life we know.
|
| And they will probably have processes and senses we don't, or
| even just don't _yet_ know any earth creatures have.
| feoren wrote:
| Light, pressure waves, chemical compositions, temperature,
| pressure, body position, magnetic field, distance (sonar) --
| what is there around us that some life on Earth is not already
| sensing? What other senses could aliens have?
| ncmncm wrote:
| We don't know, do we?
|
| We never would have even looked for a magnetic-line slope-
| angle sense without inventing compasses, _and then also_
| understanding the structure of the earth 's magnetic field.
| Likewise, we only understood echolocation after we invented
| it; before, we had no clue any animal used it. Octopods have
| no sense of joint angle. Some bugs taste what they walk on.
|
| Thinking the only interesting phenomena in the universe are
| ones we already know about, or know something useful to do
| with, is akin to the fundamental failing of TFA.
| NonContro wrote:
| Won't all extraterrestrial life just look like crabs?
|
| https://en.wikipedia.org/wiki/Carcinisation
| jnwatson wrote:
| The first life we encounter from another civilization might not
| be evolved at all. Presumably a civilization with the capability
| of interstellar travel might also have the technology to
| manipulate the underpinning of life itself.
|
| In fact, if we do discover something from another civilization,
| it is quite reasonable that it would be some sort of Von Neumann
| probe. It might be made of mechanical parts, "biological" parts,
| or something in between.
|
| A Von Neumann probe would be highly engineered, and might have no
| trace of evolution to it.
| rthomas6 wrote:
| Or it could be designed to be very small so as to efficiently
| send out at near light speed, and designed to quickly adapt and
| replicate in any hospitable environment.
|
| Maybe we are the Von Neumann probe.
| drdeadringer wrote:
| I recall a scifi story by Stephen Baxter where a human-made
| probe on Mars eventually evolved into advanced, aware,
| spacefaring Von Neumann probes. After a few million years, one
| curious probe traces serial numbers back to Earth in search of
| their creators. However, humans had devolved back into a type
| of monkey that was directly symbiotic with a literal tree of
| life. The probe concluded that such a primitive creature could
| never have developed technology, and left.
| TedDoesntTalk wrote:
| Story name?
| [deleted]
| r_police wrote:
| Evolution by Baxter
| drdeadringer wrote:
| The book 'Evolution' by Stephen Baxter.
|
| Wikipedia article here:
| https://en.wikipedia.org/wiki/Evolution_(Baxter_novel)
| JetSetWilly wrote:
| Not only that - for all we know a biological civilsiation could
| have existed 3 billion years ago which then spawned a machine
| civilisation that now has as much relation to its distant
| origins as we do to some prebiotic soup on Hadean earth.
| sandworm101 wrote:
| >> A Von Neumann probe ... might have no trace of evolution to
| it.
|
| Except that the very fact that it exists represents many
| evolved traits. If they are sending probes then their are
| either curious or expansionist, both evolved traits tied to
| competition for resources and/or survival. A species totally
| devoid of any history of evolutionary pressures wouldn't act
| that way, which is one of many possible great filters: once we
| have access to the infinite resources of space, perhaps we just
| stop caring and don't bother expanding. Such logic allows us to
| learn much simply from the existence of an otherwise silent Von
| Neumann probe.
| XorNot wrote:
| Well also, a Von Neumann probe is a type of life. It's very
| unlikely that a self-replicating machine would not develop
| it's own technological drift in the replication protocol.
| sigg3 wrote:
| In all likelihood, yes.
|
| But when dealing with infinity, we must appreciate the
| likelihood of the unlikely too.
|
| Personally, I favor the prospect of the insanely lucky idiot
| race, that clumsily and completely by chance manage to launch
| a probe so seemingly sophisticated that every sentient race
| that discovers it readily submit to its perceived
| superiority.
| sandworm101 wrote:
| There are no real infinities. The universe might be
| infinite, but the bit of it we can see and/or ever interact
| with is not (speed of light + expansion). So there are a
| finite number of stars that we will ever be able to touch
| before the universe goes dark. And the universe seems to
| have had a finite starting point. So we can calculate which
| stars may ever reach out to us. These are very big numbers,
| but they are not infinite.
|
| Unless star trek is real. Faster than light travel opens up
| the door to infinities.
| ajcp wrote:
| Even with FTL travel the heat death of the universe still
| closes the door on an "infinity" as far as things within
| it existing goes.
| mLuby wrote:
| Some forms of FTL travel also opens the door to time
| travel, so even if there is no multiverse and our
| universe has a point in its future where all energy is at
| its lowest possible state, we could still bounce around
| between the Big Bang and the heat death for quite a
| while.
| shawnz wrote:
| Unless it somehow came from nothing, then there must be some
| pathway from what came before to what they have now (thus
| evolution). It might be a long pathway, which is so long that
| it's hard for us to see the beginning from the end, but that
| doesn't invalidate the argument that it will still have
| characteristics of something that followed such a pathway.
| legrande wrote:
| > It might be made of mechanical parts, "biological" parts, or
| something in between
|
| Or just a digital clone of a once-biological being that can
| live for infinity exploring the Universe. Why would you explore
| the Universe in a meat suit?
| LaMarseillaise wrote:
| You enjoy proximity to other meat suits?
|
| Without that, it sounds to me more like hell than heaven.
| emteycz wrote:
| Why not beam yourself into a meatsuit over the internet?
| yawaworht1978 wrote:
| We humans have only our definition of life form. These are
| limited by physics and our logic. However, we can't even see the
| whole universe, with no scientific break through, we never will.
| We don't exactly know the full story of the big bang, we can't
| explain the very beginning. We don't know what happens in black
| holes, our logic rules literally breaks down there. I could well
| be that there are life forms which we couldn't even imagine,
| which are not limited by our known physics. We know a little bit
| about space time and gravity and the elements. Dark matter still
| unexplained, no universal formula for everything in sight, i have
| seen DNA mentioned, maybe some creatures do not need any DNA. Too
| many factors are unresolved, we don't know whether there have
| been, are or will be totally different species. Imagine, at one
| point in history, earth didn't even exist, before animals, there
| were only bacteria. Earth lifetime is nothing on the grand scale
| of things. Humans are a more intelligent version of very common
| mammals. With a couple more things gone wrong, like a flu or
| smarter predator animal in the past, humans might have never come
| to be. I greatly appreciate scientists and people discovering and
| accumulating the knowledge, and I understand the scientific
| methods have to be followed accurately, else we diverge into pure
| speculation. But limiting possible alien life to earth like
| planets might not be all there is.
| wuunderbar wrote:
| > Earth lifetime is nothing on the grand scale of things.
|
| Nit: Isn't the estimated age of the universe 14 billion and
| earth 4.5 billion? I wouldn't call that nothing.
| tombh wrote:
| > The universe could possibly avoid eternal heat death
| through random quantum tunnelling and quantum fluctuations,
| given the non-zero probability of producing a new Big Bang in
| roughly 10^10^10^56 years
|
| https://en.wikipedia.org/wiki/Future_of_an_expanding_univers.
| ..
| varispeed wrote:
| I used to explain to myself what was before the universe -
| that it simply didn't exist, just like myself didn't exist,
| but in fact my body is a continuation of life since its
| inception - like my parents knew their parents (or at very
| least they had a brief contact with their mothers), their
| parents knew their parents and so on back to something that
| sparked life, but that something also must have come from
| something. So still can't get my head around what was before
| the universe. I know these visualisations that show for
| example that something that has beginning and end can be
| divided infinitely, but when I picture it, this exists in
| some sort of space.
| cletus wrote:
| I expect that there are some things that are "universal" and some
| that aren't.
|
| For example, if life--any life--forms on a planet, it is likely
| that some macro-organisms will evolve that consume other
| organisms.
|
| On Earth we have plants that are eaten by animals that are eaten
| by other animals and so forth and these all act as a form of
| "battery" in that solar power is converted into energy and
| increasingly stored in larger "blobs". This is almost necessary
| for large life to exist. Well, for carnivores at least (eg many
| whales eat krill and there are a bunch of filter-feeders).
|
| So the chemistry of life elsewhere may be similar or it may be
| totally different but something like a carnivorous trait is I
| think almost inevitable.
|
| Once you have that then certain other traits became almost
| inevitable. Flight, for example. It may be that flight is
| impossible given local conditions (eg high gravity, atmosphere or
| the lack thereof). That doesn't mean we'll end up with feathers
| and birds per se but evolutionary pressure will likely mean
| available niches are filled. On Earth almost every environment
| has life, only really excluding the coldest, driest, highest and
| deepest of places.
|
| Also, consider sensory organs. I expect the ability to detect
| parts of the EM spectrum, sound, taste/smell and tactile feedback
| will all likely evolve with sufficient time. And that itself has
| consequences for what life looks like.
| xtracto wrote:
| Great read, thanks. This is a very interesting subject to me. A
| couple of years ago I read a theory about alien life that was a
| bit different from this:
|
| Given the age of our universe, sun, earth and humans:
| Universe 14 000 million Sun 4 600 million
| Earth 4 550 million Earth Life 3 500 million
| Humans .2 million (200,000 years)
|
| The probability of some alien life being within say, a range of
| [-.5 mllion, .5 million] of the life on earth is VERY slim. It is
| most likely that life out there is either in very early stages
| (protezoric) or that it is way farther than our current form (how
| will humanity look like in say, another 500,000 years?, assuming
| it continues to exist and evolve)
| jbotz wrote:
| First, the article wasn't about human-like technological
| civilization, but just about life in general. And there are
| species of animals alive today that have hardly changed in 100s
| of millions of years. So Kershenbaum would be right if we found
| some life-forms that vaguely resembled for example a Coelacanth
| on some exoplanet.
|
| Second, you're ignoring the fact that life as we think of it
| can really only evolve around at least 3rd-generation stars
| because you need enough heavy elements. That cuts the age of
| the "life-capable" universe by at least half, so the window of
| relatively modern life on earth with respect to the age of the
| life-capable Universe really isn't _that_ small... let 's say
| 350My out of 7Gy, so about 5%.
| TedDoesntTalk wrote:
| What are 3rd generation stars, and why do we believe that
| life "as we think of it"can only evolve around them?
| dogma1138 wrote:
| Stars that formed in nebulae that had 2 previous cycles of
| star formation and super novae.
|
| This means that the star's solar system at that point has
| sufficient quantities of heavy elements which cannot be
| produced by stellar fusion, as these elements are produced
| by super novae and from solar radiation.
|
| Basically all the neutrons that are produced when a star
| goes boom create the elements that are above iron in the
| periodic table.
| Jerrrry wrote:
| Familar higher orders of complexity emerge far easier
| within systems with more states.
|
| Due to our physical laws elements with larger rooms for
| reaction via chemistry are familar.
|
| The chances of a replicating agent just anthropologically
| emerging from the surface of a 2nd generation hydrogen
| dominant star with an accumulation disc composed of little
| higher orders elements is inconceivably less likely than
| the relative petri dish organic molecules provide.
| AnimalMuppet wrote:
| First generation stars are stars that are formed from big-
| bang gas - mostly hydrogen, a bit of helium, a trace of
| lithium, and _nothing_ more. Second generation stars are
| formed from the gasses blown off by the novas of first
| generation stars. Third generation stars are from the novas
| of second generation stars.
|
| I suspect that the claim that life as we know it can only
| evolve there is because life as we know it needs a wide
| variety of chemical elements. We need carbon and oxygen, of
| course, but also iron and calcium and magnesium and
| potassium and so on. You're not going to get that around a
| first generation star. You might not get _enough_ of it
| around a second generation star.
| iamgopal wrote:
| can by products of first gen / second gen star creates
| life-form that is alive in whatever sense we think
| something is alive, but radically different in whatever
| capability we think a life form must have ? What is alive
| in the sense for us to search in universe ?
| dogma1138 wrote:
| First gen unlikely unless life can form from the elements
| created during the Big Bang and w/e minute amounts were
| created due to solar radiation during the life of the
| star.
|
| And most importantly first gen stars can't form planets
| other than gas giants and even gas giants are
| questionable because our current understanding that other
| than a few failed stars these also usually require a
| heavy element core as a seed.
|
| 2nd gen stars are a possibility in a region of space that
| had a lot of 1st gen stars to nova and there might be
| sufficient amount of heavy elements already there to form
| a solar system.
|
| So unless life can form from hydrogen, helium, lithium
| and beryllium then no life in 1st gen stars.
|
| 2nd gen is highly dependent on the region of space
| although I would posture that any region active enough to
| create sufficient amount of heavy elements would probably
| remain too active during the 2nd generation for life or
| at least complex life to form.
| roberttod wrote:
| Unless we just happen to have evolved very early on compared to
| what's normal, we should expect a lot of intelligent life with
| just a little bit of variance on these numbers. And some of
| that could easily be millions of years old. Interestingly, even
| if a life form populated new solar systems at a rate of a
| thousand years per system (where each populated solar system in
| turn populates more of them), they'd still fill up the Galaxy
| in only a couple million years.
| dTal wrote:
| Unless "intelligent" life inevitably renders its local
| environment uninhabitable and collapses in short order - a
| proposition looking more likely by the day. It may be that
| the intelligence required to maximally exploit the local
| negentropy is strictly less than the intelligence required to
| _not_ do that, despite being able to. Indeed it 's difficult
| to see how the trait of "behaving responsibly with an entire
| planet" could evolve - the selection pressure is rather all-
| or-nothing.
| revscat wrote:
| This is my belief as well, although slightly different in
| how I phrase it: humans are incapable of seeing much beyond
| their own selfish desires, and as a result will wind up
| causing their own extermination. The denial of death is
| widespread and understandable: to truly consider
| existential demise is exhausting, and I suspect has been
| backgrounded for simple evolutionary reasons.
|
| Regardless, the species is naturally incapable of averting
| averting crises that are foreseeable but distant.
| fleddr wrote:
| Why is intelligence seen as some inescapable playbook of
| evolution?
|
| Evolution has no agenda or goals, other than to select for
| survival. Most species on this planet have a low intelligence
| yet are successful, and don't seem to evolve into the
| direction of intelligence.
| sliken wrote:
| That makes it sounds like it took 1 billion years for life to
| form. According to timelines I've read about (based on
| scientific papers) it took around 800M-900M years for the heavy
| bombardment to stop, and temperatures reduced similar to those
| of today. So once an environment friendly to life appeared,
| life appeared quickly.
| TedDoesntTalk wrote:
| His article completely ignores the possibility of engineered
| life. Engineered life can bypass evolution and natural
| selection, even if the species responsible for the engineering
| was a product of evolution.
| dogma1138 wrote:
| Engineered life still follows evolutionary pressure and
| natural selection it just might not hit the same walls as
| life that is only driven forth by random mutations and
| opportunistic gene exchange does.
| piyh wrote:
| Strong arguments can be made that the ability to become a
| multi-planetary civilization requires you to master the tech
| tree that includes engineered life.
| xwolfi wrote:
| Heh and what if the engineer even introduces evolution and
| what he truly engineers is code-based chemical cells that can
| conquer, survive, evolve and expand from anywhere ? :D
|
| I'd do a life myself, I'd make it post-metallic, post-
| silicon, post static: I'd make it use water and carbon, so
| that it can exist everywhere. I would make it so that it can
| become intelligent on a small time scale, say a few billion
| years, all on its own, from scratch, on any rock :D
|
| Not saying we have an engineer, but you think of engineered
| life as you are now as a simple software programmer. But an
| engineer in 500k years trying to expand more, would probably
| think of chemical automata that can evolve and adapt in harsh
| conditions. Say for instance if humanity decided it would be
| enjoyable for life to exist on Jupiter. It'd have to make
| something that can try a lot of variations with a very simple
| first formula to consume whatever gas there is there and
| survive whatever pressure.
| piyh wrote:
| It'd be like explorers dropping goats on islands to come
| back to harvest them later.
| jacquesm wrote:
| There are quite a few SF stories around this theme.
| jacquesm wrote:
| Creationists may be on to something after all ;)
| Koshkin wrote:
| But, the usual: Is the creator a lifeform?
| willis936 wrote:
| This is assuming independent genesis. Panspermia has a lot of
| merit.
| machiaweliczny wrote:
| I think terdigrades might already be alien. How they evolved
| on earth?
| stefs wrote:
| tardigrades might have some very cool properties, but
| nothing out of the ordinary.
| superduperycomb wrote:
| I believe if you look at their genetics they fit snugly
| within the tree of life
| andruby wrote:
| What would be the odds that other planets/habitats have a
| similar "tree of life"? I don't know. Given the huge
| number of similarities in DNA, I'd say it's extremely
| small.
| bumby wrote:
| I don't want to speak for the OP but I read their comment
| as "why did they evolve certain features that wouldn't
| have be reasonable given the evolutionary pressures of
| earth?" E.g., their ability to survive high levels of
| radiation or vacuum.
|
| There's some speculation that a large amount of their
| genetics were transferred from other animals.[1] I wonder
| how much this muddles the tracing through the
| evolutionary tree.
|
| [1] https://www.pnas.org/content/112/52/15976.abstract
| someguyorother wrote:
| > E.g., their ability to survive high levels of radiation
| or vacuum.
|
| If I recall correctly, the tardigrades (and extremophiles
| like D. radiodurans) have evolved to handle damage
| brought on by desiccation. As a fortunate side-effect,
| this general robustness also protects against radiation.
| rozab wrote:
| This is one of my favourite websites, and I share it all
| the time:
|
| https://www.onezoom.org/life.html/@=111445?img=best_any&a
| nim...
|
| (hopefully that links to the right place)
| echelon wrote:
| Panspermia is fascinating conjecture.
|
| The preferred chirality of organic molecules could absolutely
| have arisen by chance, but it's an interesting to see this in
| meteorites.
|
| On the unrelated subject of handedness, I saw an interesting
| thread on Twitter today [1] speaking about how we're starting
| to synthesize reverse chirality polymers and enzymes, most
| notably DNA and replication enzymes.
|
| There are a lot of interesting implications.
|
| You can't get rid of L-DNA without reverse DNase, leading to
| an accumulation of information and transcription. So they
| need to remake all the enzyme steroisomers.
|
| That alone is interesting, but you can take it further to the
| limit and produce reverse biology that synthesizes reverse
| sugars that can't be metabolized by much of extant life [2].
| Suddenly a lab-escaped reverse autotroph can out-compete all
| of us right-handed lifeforms because nothing can eat them.
| Bacteria, plankton, the entire food web collapses. When we
| have nothing left to fish or farm, we die too.
|
| Never thought nanotech's grey goo was plausible. Now I see
| something that rhymes with it, and I could see it happening
| within our lifetimes.
|
| It'd make a crazy MAD bioweapon on par with or potentially
| worse than nukes.
|
| Wild tangent, sorry.
|
| [1] https://twitter.com/eigenrobot/status/1420952351968432130
|
| [2] https://twitter.com/prawncis/status/1420982623048925187
| piyh wrote:
| A MAD weapon like that just becomes an AD weapon. A nuclear
| lab leak kills under 1,000 people. A living weapon lab leak
| would kill (nearly) every other living thing.
| radicaldreamer wrote:
| I'm getting similar vibes to out of control gene drives
| created with crispr...
| bookofsand wrote:
| See also
| https://en.wikipedia.org/wiki/Great_Oxidation_Event.
|
| > Such negative values occurring shortly after the GOE
| require a rapid reduction in primary productivity of >80%,
| although even larger reductions are plausible. Given that
| these data imply a collapse in primary productivity rather
| than export efficiency, the trigger for this shift in the
| Earth system must reflect a change in the availability of
| nutrients, such as phosphorus. Cumulatively, these data
| highlight that Earth's GOE is a tale of feast and famine: A
| geologically unprecedented reduction in the size of the
| biosphere occurred across the end-GOE transition.
|
| https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6717284
| wizzwizz4 wrote:
| > _because nothing can eat them_
|
| But I assume they're not immune-invulnerable.
| echelon wrote:
| Where did the reverse viruses that can bind to their
| cellular receptors and co-opt their reverse cellular
| metabolism evolve?
|
| To be clear, evolution of viruses is probably inevitable.
| But on what time scale does it take for them to arrive ex
| nihilo? Millennia? Longer?
| imglorp wrote:
| Yes and there are two types of panspermia.
|
| The first type is incidental: we've already encountered
| meteorites from Mars and the Moon, for example, so it's not
| hard to imagine life bearing material arriving that way.
|
| The second would be intentional: either ET seeds planets or
| merely visits them with contaminated boots or probes.
|
| Either way, we would pick up some DNA from offworld.
| JoeAltmaier wrote:
| The Cambrian Explosion shows that life can do all sorts of
| divergent things. The similarity of many current life forms (e.g.
| fish that are totally unrelated but work about the same) has more
| to do with environmental pressures producing similar results,
| that it has to do with what's possible?
| candlemas wrote:
| Science is finally catching up with UFOlogy:
| https://thebiggeststudy.blogspot.com/2009/10/what-will-they-...
| ignoranceprior wrote:
| If Star Trek taught me anything, it's that most aliens look like
| humans, except for some bumps on their forehead. Hodgkin's Law of
| Parallel Planetary Development.
| ASalazarMX wrote:
| Star Trek TNG kind of lampshaded that in "The Chase", where its
| is revealed that alien species are similar and biologically
| compatible because they share a common humanoid ancestor.
|
| https://memory-alpha.fandom.com/wiki/The_Chase_(episode)
| roberttod wrote:
| I hope that also applies to the evolution of morals for
| intelligent lifeforms. I think it's safer to assume any aliens
| will have bad intentions but maybe any lifeform that can build
| interstellar technology has come to the same conclusions that we
| (albeit slowly) are coming to.
| benlivengood wrote:
| My optimism says that radical consensual transhumanism _might_
| be a universal Schelling point and that if humanity reaches
| that point we 'd fit fairly well into any advanced alien
| culture that reached the same values. Probably the biggest
| value difference at that point would be the
| morality/consciousness thresholds for tiers of personhood.
|
| I don't think any morally advanced culture would be willing to
| accept an indefinite policy of "live and let live" between the
| cultures as a whole; there are some injustices (slavery,
| murder, torture) that wouldn't be tolerable to exist in the
| known universe.
| goatlover wrote:
| But that raises a moral conundrum of interference with an
| alien culture's development and impact on their world. On
| Earth, intervention in other societies has not gone over that
| well. If you have relatively equal societies in terms of
| technology, then you risk devastating warfare.
| fairity wrote:
| I think it's safe to assume any highly evolved alien species
| will have moral constructs that support self-preservation.
|
| Whether those morals extend to preserving other intelligent
| life forms (I.e. humans) seems unlikely since the prosperity of
| other life forms will inevitably lead to more competition for
| scarce resources.
|
| The fact that human moral constructs apply to other intelligent
| species seems to be a bug that arises solely from the fact that
| we're currently capable of out competing all other intelligent
| species.
| namarie wrote:
| What exactly is a "scarce resource" on a galactic scale? I'd
| think there isn't one.
| avaldes wrote:
| Habitable planets with the exact chemistry to support your
| species without expensive or slow terraforming.
| WitCanStain wrote:
| This assumes that the hypothetical aliens draw (ultimately
| artificial and arbitrary) distinctions between themselves and
| other intelligent species. Who knows, they might consider us,
| another intelligent species, to be 'one of them' in some
| sense and thus deserving of protection.
| caymanjim wrote:
| I don't think any sophisticated intelligent beings could evolve
| without their primary social interaction being cooperative. You
| can't build a spaceship if you don't learn to get along with
| others. You wouldn't evolve complex thought or even language
| without social pressure. This doesn't necessarily automatically
| translate to cross-species cooperation, or even intra-species,
| as evidenced by our own history of wars and subjugation, but in
| the grand scheme of things, our baseline is trending towards
| more peaceful existence. I expect the same pressures that would
| make aliens follow the same form factor as us would also drive
| them towards similar social constructs.
| avaldes wrote:
| > You can't build a spaceship if you don't learn to get along
| with others.
|
| We literally built rockets and started spacial exploration
| out of a pissing contest. It has been clearly on mankind
| history that we don't need to cooperate as a unified peaceful
| race to advance technological progress.
| actusual wrote:
| This is interesting, and I have a more mathematical way of
| thinking about this.
|
| If we were somehow able to segment evolutionary pressures, and
| normalize their values such that they sum to one, I'd hypothesize
| that as the average evolutionary pressure goes to zero (meaning
| high number of evolutionary pressures that are generally
| uniformly distributed), then this author's hypothesis is true.
| But as the average evolutionary pressure grows (fewer pressures,
| or highly skewed distribution of pressures), I imagine it would
| lead to VERY different looking life. I'd also hypothesize that as
| the average value increases, it leads to system instability.
| [deleted]
| ramboldio wrote:
| If any life on earth was extraterrestrial, I would bet on fungi.
| It somehow works too well.
| actusual wrote:
| My grass is in heavy agreement. Mushrooms pop up in my yard
| within hours of watering.
| ssully wrote:
| While it's technically not a fungus, I had my first
| experience with Fuligo septica, or Dog Vomit mold. My wife
| were gardening in the late evening and went inside as it got
| dark. About an hour later I let the dogs out and this yellow
| mass was in the mulch, probably about 6x5" in size. We
| assumed it was vomit from a racoon or something, but figured
| it out when it grew back the next day (in two spots this
| time). I would remove it every morning, but it would grow
| back for the entire week in different spots in the mulch. It
| was fascinating, but incredibly gross and kind of creepy!
| larkost wrote:
| Note that the mushroom in question has been growing just
| below the surface for some time. The part we are used to
| thinking of as a mushroom is, on many species, something like
| an inflatable flower that is used to release their spores. It
| is built just below ground over a long time, then inflated at
| the right moment (rains), and then abandoned while the below-
| ground main body starts working up the energy to do it all
| again.
| ASalazarMX wrote:
| Unfortunately for them, many are quite tasty.
| fleddr wrote:
| Joke's on you. When you eat a mushroom, you eat the fruiting
| body of the fungus. The mycellium is the real organism, and
| lives on just fine.
| ahurmazda wrote:
| biggest hope for the survival of human race in the face of an
| alien onslaught is that we taste like yummy chicken. this
| way, they will keep us around for a long time
| pbae wrote:
| Being farmed in perpetuity seems like a worse fate than
| extermination.
| throwawayayay55 wrote:
| Consider that you're thinking too much of "cow farming"
| when you think of human farming.
|
| No, humans are too useful to just eat! Even for menial
| tasks. You could think of slavery as a primitive form of
| human farming, but it's inefficient: being too harshly
| treated means poor health and mental performance, which
| means the tasks they can work in are limited. No, the
| farmers that would be worthy of farming humans would be
| more astute.
|
| It's far more efficient to let a farmed kind live just
| comfortably enough to be healthy and develop themselves
| (free range), as long as they (1) are imposed with an
| element of scarcity that will force them to struggle to
| be useful in exchange for the scarce element and (2) the
| farmer is positioned in such a way that they extract
| value from these useful activities, with no downside.
|
| As a bonus, because there's an element of competition for
| the scarcity, the farmed kind will police themselves
| (fairly or not), and band together, cooperating to
| generate an oversized portion of the scarce element at a
| certain level of increased risk for the leaders of the
| band - we can call them stakeholders. Winning
| stakeholders will be rewarded with increased amounts of
| the scarce element, and losers will be punished with a
| loss of scarce elements.
|
| Extraordinarily successful stakeholders would be rewarded
| with benefits, and benefit not unlike the farmers - they
| are to be rewarded for their feats.
|
| Those that are successful enough will be invited to
| travel to the farmers' homeland riding on a giant space
| phallus...
| godelski wrote:
| There's a lot of "we only have humans for our definition" or "we
| only have Earth life" but I think these comments miss a lot.
| Let's really break down what we would expect to see in
| intelligent and comparable (or even more advanced) life from
| extraterrestrials.
|
| We know they have to use tools. You might point to crows,
| dolphins, or others and note that they use tools. But they don't
| in the same way that apes do. We're much better equipped to
| manipulate objects by using hands than using a mouth. Tentacles
| might be a better comparison but actually fingers allow for a lot
| of fine manipulation. Though I'm sure octopi could make tools
| that better work for them there's some mechanical reasons to
| believe hands are better. I mean there's the fractal nature of an
| arm helps with fine manipulation.
|
| We know there's things like milk that help impart high nutrient
| content diets to young and there are correlations between lactate
| and fat to brain mass. We know this is a more efficient delivery
| system than say what birds to: eat, per-digest, and regurgitate.
| We actually expend a lot of energy to create milk.
|
| These are just two (very incomplete and naive) examples, but what
| I'm trying to say is that not all options are equally likely.
| Maybe it won't be a hand. Maybe it'll be a tentacle with
| fractaling appendages (personally I wouldn't expect this because
| such a system is more complex) but I wouldn't expect something
| with (non-vestigial) wings, especially like a bat wing. Membranes
| can be easily punctured when working with objects and makes it
| hard to reach into confined spaces because of the necessity for
| large surface area to be able to fly.
|
| So while yes, we only have Earth as a reference point we also
| have a lot of physics, biology, evolutionary pressures, game
| theory, and an understanding of tools and mechanics to lean on as
| well. I do think this does provide some restrictions to what is
| likely. _Not everything is on the table or equally likely._ I
| don't think it's naive to think that we have some good ideas of
| some basic characteristics that alien life would look like (we
| can apply similar ideas to non-highly intelligent life). I think
| it's naive to believe that anything is possible. These are claims
| that "sound smart" but are very naive and actually demonstrate a
| lack of basic knowledge.
|
| So can we stop pretending like astrobiologists are idiots and
| haven't thought about this stuff? I don't know about you but I
| trust them more than I trust myself. They've spent significantly
| more time thinking about these things and have a far better
| background than us (except the handful of biologists and
| astrobiologists that are here).
| drdeadringer wrote:
| I recall a Youtube video [can't find link right now] between
| Richard Dawkins and Neil deGrasse Tyson where they discuss
| probable expectations of alien biology based on
| parallel//independent evolution on Earth. Eyes were one example.
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