5 ms·

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

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)

willis936 5y ago
This is assuming independent genesis. Panspermia has a lot of merit.
- machiaweliczny 5y ago
  I think terdigrades might already be alien. How they evolved on earth?
  - superduperycomb 5y ago
    I believe if you look at their genetics they fit snugly within the tree of life
    - andruby 5y ago
      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 5y ago
      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 https://www.pnas.org/content/112/52/15976.abstract
      - someguyorother 5y ago
        > 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 5y ago
      This is one of my favourite websites, and I share it all the time: https://www.onezoom.org/life.html/@=111445?img=best_any&anim=flight#x-954,y34,w6.8520 https://www.onezoom.org/life.html/@=111445?img=best_any&anim... (hopefully that links to the right place)
  - stefs 5y ago
    tardigrades might have some very cool properties, but nothing out of the ordinary.
- echelon 5y ago
  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 https://twitter.com/eigenrobot/status/1420952351968432130 [2] https://twitter.com/prawncis/status/1420982623048925187 https://twitter.com/prawncis/status/1420982623048925187
  - wizzwizz4 5y ago
    > because nothing can eat them But I assume they're not immune-invulnerable.
    - echelon 5y ago
      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?
  - radicaldreamer 5y ago
    I'm getting similar vibes to out of control gene drives created with crispr...
  - 5y ago
- imglorp 5y ago
  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.
roberttod 5y ago
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 5y ago
  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 5y ago
    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 5y ago
  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.
  - roberttod 5y ago
    For every planet with intelligent life, there could be many more without it, no idea what that relationship might look like. I'm not suggesting it's the norm.
jbotz 5y ago
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 5y ago
  What are 3rd generation stars, and why do we believe that life “as we think of it”can only evolve around them?
  - AnimalMuppet 5y ago
    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 5y ago
      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 ?
TedDoesntTalk 5y ago
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.
- piyh 5y ago
  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 5y ago
  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 5y ago
    It'd be like explorers dropping goats on islands to come back to harvest them later.
    - jacquesm 5y ago
      There are quite a few SF stories around this theme.
  - jacquesm 5y ago
    Creationists may be on to something after all ;)
sliken 5y ago
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.

willis936 5y ago

This is assuming independent genesis. Panspermia has a lot of merit.

machiaweliczny 5y ago
I think terdigrades might already be alien. How they evolved on earth?
- superduperycomb 5y ago
  I believe if you look at their genetics they fit snugly within the tree of life
  - andruby 5y ago
    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 5y ago
    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 https://www.pnas.org/content/112/52/15976.abstract
    - someguyorother 5y ago
      > 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 5y ago
    This is one of my favourite websites, and I share it all the time: https://www.onezoom.org/life.html/@=111445?img=best_any&anim=flight#x-954,y34,w6.8520 https://www.onezoom.org/life.html/@=111445?img=best_any&anim... (hopefully that links to the right place)
- stefs 5y ago
  tardigrades might have some very cool properties, but nothing out of the ordinary.
echelon 5y ago
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 https://twitter.com/eigenrobot/status/1420952351968432130 [2] https://twitter.com/prawncis/status/1420982623048925187 https://twitter.com/prawncis/status/1420982623048925187
- wizzwizz4 5y ago
  > because nothing can eat them But I assume they're not immune-invulnerable.
  - echelon 5y ago
    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?
- radicaldreamer 5y ago
  I'm getting similar vibes to out of control gene drives created with crispr...
- 5y ago
imglorp 5y ago
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.

roberttod 5y ago

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 5y ago
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 5y ago
  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 5y ago
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.
- roberttod 5y ago
  For every planet with intelligent life, there could be many more without it, no idea what that relationship might look like. I'm not suggesting it's the norm.

jbotz 5y ago

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 5y ago
What are 3rd generation stars, and why do we believe that life “as we think of it”can only evolve around them?
- AnimalMuppet 5y ago
  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 5y ago
    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 ?

TedDoesntTalk 5y ago

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.

piyh 5y ago
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 5y ago
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 5y ago
  It'd be like explorers dropping goats on islands to come back to harvest them later.
  - jacquesm 5y ago
    There are quite a few SF stories around this theme.
- jacquesm 5y ago
  Creationists may be on to something after all ;)

sliken 5y ago

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.