Assuming multi-cellular life exists elsewhere in the universe, what do you think it looks like?

[rousseau]

Except that, in the history of Earth alone, very different animals have occupied more or less in the same environments. Since the Cretacean, bony fish, and specifically  perciformes (an order that only arose in the late Cretacean and comprises 40% of all living fish species) have taken niches that where previously occupied by ammonites, and before them by trilobites.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

They are also moving along an evolutionary line while in similar environments.

Not necessarily - the trilobites fell victim to a mass extinction event that killed of some 95% of species at the time.

So we could assume that varying species are able to live in the same environment, but a similar evolutionary line might progress in a similar planet.

You're dangerously close to teleological thinking here.

Not really. What I mean is that given similar conditions, not only are similar life-forms going to come into existence, but it's also likely that they'll start in a similar place, and move in a similar direction.

For instance, life is more likely to start in water than on land, and assuming land exists, it should eventually move onto land with an amphibian like appearance, and so on.

That's not a guarantee that intelligent life arises, but it's very likely that intelligent life would arise eventually given the right circumstances, as intelligence seems to be a great driver in reproductive success.

 

[dystopian]

Except that, in the history of Earth alone, very different animals have occupied more or less in the same environments. Since the Cretacean, bony fish, and specifically  perciformes (an order that only arose in the late Cretacean and comprises 40% of all living fish species) have taken niches that where previously occupied by ammonites, and before them by trilobites.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

They are also moving along an evolutionary line while in similar environments.

Not necessarily - the trilobites fell victim to a mass extinction event that killed of some 95% of species at the time.

So we could assume that varying species are able to live in the same environment, but a similar evolutionary line might progress in a similar planet.

You're dangerously close to teleological thinking here.

Not really. What I mean is that given similar conditions, not only are similar life-forms going to come into existence, but it's also likely that they'll start in a similar place, and move in a similar direction.

For instance, life is more likely to start in water than on land, and assuming land exists, it should eventually move onto land with an amphibian like appearance, and so on.

That's not a guarantee that intelligent life arises, but it's very likely that intelligent life would arise eventually given the right circumstances, as intelligence seems to be a great driver in reproductive success.

I tend to agree. These aren't absolutes, but given a large sampleset of worlds with life, we should still see certain patterns emerge. More than likely, earth life would fit within this pattern; though I suppose we could theoretically be an anomaly.

 

[Jokodo]

I don't consider these sufficiently different. On the scale of great variaty we already have they are very similar.
I mean I expect to see trilobite like things on every sufficiently life rich planet.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

No, I did provide rational argument. You merely failed to provide counter-argument.

So you say that trilobites, ammonites, and fish are sufficiently similar that they count as one and the same "best design", but when it comes to intelligent life, you are confident expecting them to be something much more specific - "be-pedal apes" of a specific size range.

That's not rational.

As far as ocean concerned, evolution has tried virtually everything with great success.
As for intelligent species then there is only one such specie on planet earth, ask yourself why?

Maybe because it takes a rather narrow set of circumstances for there to be an evolutionarily successful path that leads to one. This doesn't imply or even suggest that there's only one such path. Not even close.

you really expect birds for example to evolve true human-like intelligence? why would the do that?

And if we were super-intelligent corvids, you would be asking right now, with the same degree of rightousness and the exact same amount of empirical backing: "you really expect monkeys for example to evolve true crow-like intelligence? why would the do that?"

 

[Jokodo]

Except that, in the history of Earth alone, very different animals have occupied more or less in the same environments. Since the Cretacean, bony fish, and specifically  perciformes (an order that only arose in the late Cretacean and comprises 40% of all living fish species) have taken niches that where previously occupied by ammonites, and before them by trilobites.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

They are also moving along an evolutionary line while in similar environments.

Not necessarily - the trilobites fell victim to a mass extinction event that killed of some 95% of species at the time.

So we could assume that varying species are able to live in the same environment, but a similar evolutionary line might progress in a similar planet.

You're dangerously close to teleological thinking here.

Not really. What I mean is that given similar conditions, not only are similar life-forms going to come into existence, but it's also likely that they'll start in a similar place, and move in a similar direction.

For instance, life is more likely to start in water than on land, and assuming land exists, it should eventually move onto land with an amphibian like appearance, and so on.

That's not a guarantee that intelligent life arises, but it's very likely that intelligent life would arise eventually given the right circumstances, as intelligence seems to be a great driver in reproductive success.

What makes you think so? For approximately 99% of our history as a distinct line from the chimpanzee one, we've been outnumbered by baboon-like monkeys which were in turn outnumbered by springbok-like ungulates.

 

[SLD]

So why haven't exoskeleton animals evolved that are much larger? Granted there can't be a land squid, but why isn't there an ant species as large as say a squirrel? I don't know anything in the laws of physics that would prohibit such. But maybe it is just very hard to build a large exoskeleton. I would think that overall the permutations are somewhat limited for the development of advanced lifeforms. I saw a biological commentary on Starwars and it made it clear that the creatures were too outlandish to evolve, in part because they had so many strange appendages. Too easy to take off and get one in trouble. But exoskeletons vs Chordate type structure?

SLD

 

[barbos]

I don't consider these sufficiently different. On the scale of great variaty we already have they are very similar.
I mean I expect to see trilobite like things on every sufficiently life rich planet.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

No, I did provide rational argument. You merely failed to provide counter-argument.

So you say that trilobites, ammonites, and fish are sufficiently similar that they count as one and the same "best design", but when it comes to intelligent life, you are confident expecting them to be something much more specific - "be-pedal apes" of a specific size range.

That's not rational.

As far as ocean concerned, evolution has tried virtually everything with great success.
As for intelligent species then there is only one such specie on planet earth, ask yourself why?

Maybe because it takes a rather narrow set of circumstances for there to be an evolutionarily successful path that leads to one. This doesn't imply or even suggest that there's only one such path. Not even close.

But every path has been tried.

you really expect birds for example to evolve true human-like intelligence? why would they do that?

And if we were super-intelligent corvids, you would be asking right now, with the same degree of rightousness and the exact same amount of empirical backing: "you really expect monkeys for example to evolve true crow-like intelligence? why would the do that?"

You have not answered my question.
There are no "ifs" here, we are intelligent and birds are not. And there is a reason why it is so.

 

[dystopian]

So why haven't exoskeleton animals evolved that are much larger? Granted there can't be a land squid, but why isn't there an ant species as large as say a squirrel? I don't know anything in the laws of physics that would prohibit such.

Actually, for quite similar reasons. Biology can't really produce the combination of muscles, internal organs, and joins required to create a large exoskeleton creature; any such creature would collapse under its own weight. A squirrel sized land-dwelling exoskeleton creature might be doable, but it's pushing it. The largest spiders in existence are at about the upper size limit of land-dwelling exoskeleton lifeforms.

 

[barbos]

Insects are mostly limited by their respiratory system.
exoskeleton is a drawback too but not immediate.
crabs have exoskeleton and they can be quite large, don't know how they breath though

 

[Jokodo]

I don't consider these sufficiently different. On the scale of great variaty we already have they are very similar.
I mean I expect to see trilobite like things on every sufficiently life rich planet.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

No, I did provide rational argument. You merely failed to provide counter-argument.

So you say that trilobites, ammonites, and fish are sufficiently similar that they count as one and the same "best design", but when it comes to intelligent life, you are confident expecting them to be something much more specific - "be-pedal apes" of a specific size range.

That's not rational.

As far as ocean concerned, evolution has tried virtually everything with great success.
As for intelligent species then there is only one such specie on planet earth, ask yourself why?

Maybe because it takes a rather narrow set of circumstances for there to be an evolutionarily successful path that leads to one. This doesn't imply or even suggest that there's only one such path. Not even close.

But every path has been tried.

What's the logic behind claiming that, 3.5 billion years after the origin of life on earth and 0.53 billion years after the Cambrian Explosion, "every path has been tried"? Why or why not would the same logic allow you to say the same thing (in hindsight, demonstrably wrong) 3.43 Ga after the origin of life and 0.46 Ga after the Cambrian Explosion, i.e. in the late Cretacean? Do you believe the current stage of evolution on Earth is some kind of goal state?

you really expect birds for example to evolve true human-like intelligence? why would they do that?

And if we were super-intelligent corvids, you would be asking right now, with the same degree of rightousness and the exact same amount of empirical backing: "you really expect monkeys for example to evolve true crow-like intelligence? why would the do that?"

You have not answered my question.
There are no "ifs" here, we are intelligent and birds are not. And there is a reason why it is so.

You haven't demonstrated that there is any reason beyond historical contingencies. All you are saying could equally be said if it where the other way round. There was no particular reason to expect monkeys to evolve "true human-like intelligence", as we now call it, 10 or 20 million years ago. I can not give you a specific a priori reason why crows would evolve "human-like intelligence" - but that's not an argument that only monkeys have the prerequisite. Indeed, it's hard to explain even after the fact why monkeys of all groups did evolve "human-like intelligence".

 

[Jokodo]

So why haven't exoskeleton animals evolved that are much larger? Granted there can't be a land squid, but why isn't there an ant species as large as say a squirrel? I don't know anything in the laws of physics that would prohibit such.

Actually, for quite similar reasons. Biology can't really produce the combination of muscles, internal organs, and joins required to create a large exoskeleton creature; any such creature would collapse under its own weight. A squirrel sized land-dwelling exoskeleton creature might be doable, but it's pushing it. The largest spiders in existence are at about the upper size limit of land-dwelling exoskeleton lifeforms.

The  Coconut crab can weigh up to 4.1kg - that's an order of magnitude above your typical squirrel.

 

[fromderinside]

There are no "ifs" here, we are intelligent and birds are not. And there is a reason why it is so.

Putting on my best Jon Stewart aire: "Do go on". (six men in the background who have just finished tying the thirteen loop knot now advance on Barbos with glee in their eyes. One tells Jokodo to "please step aside")

 

[dystopian]

Actually, for quite similar reasons. Biology can't really produce the combination of muscles, internal organs, and joins required to create a large exoskeleton creature; any such creature would collapse under its own weight. A squirrel sized land-dwelling exoskeleton creature might be doable, but it's pushing it. The largest spiders in existence are at about the upper size limit of land-dwelling exoskeleton lifeforms.

The  Coconut crab can weigh up to 4.1kg - that's an order of magnitude above your typical squirrel.

I stand corrected. Still, that does seem to be the upper limit. Part of the reason why it seems to have been able to grow as big as it has is because of its lung, which is something most exoskeleton creatures lack.

 

[rousseau]

Except that, in the history of Earth alone, very different animals have occupied more or less in the same environments. Since the Cretacean, bony fish, and specifically  perciformes (an order that only arose in the late Cretacean and comprises 40% of all living fish species) have taken niches that where previously occupied by ammonites, and before them by trilobites.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

They are also moving along an evolutionary line while in similar environments.

Not necessarily - the trilobites fell victim to a mass extinction event that killed of some 95% of species at the time.

So we could assume that varying species are able to live in the same environment, but a similar evolutionary line might progress in a similar planet.

You're dangerously close to teleological thinking here.

Not really. What I mean is that given similar conditions, not only are similar life-forms going to come into existence, but it's also likely that they'll start in a similar place, and move in a similar direction.

For instance, life is more likely to start in water than on land, and assuming land exists, it should eventually move onto land with an amphibian like appearance, and so on.

That's not a guarantee that intelligent life arises, but it's very likely that intelligent life would arise eventually given the right circumstances, as intelligence seems to be a great driver in reproductive success.

What makes you think so? For approximately 99% of our history as a distinct line from the chimpanzee one, we've been outnumbered by baboon-like monkeys which were in turn outnumbered by springbok-like ungulates.

Humans != the only intelligent species

- - - Updated - - -

So why haven't exoskeleton animals evolved that are much larger? Granted there can't be a land squid, but why isn't there an ant species as large as say a squirrel? I don't know anything in the laws of physics that would prohibit such. But maybe it is just very hard to build a large exoskeleton. I would think that overall the permutations are somewhat limited for the development of advanced lifeforms. I saw a biological commentary on Starwars and it made it clear that the creatures were too outlandish to evolve, in part because they had so many strange appendages. Too easy to take off and get one in trouble. But exoskeletons vs Chordate type structure?

SLD

I would imagine that as insects have evolved to be larger they would be more likely to be eaten.

 

[Kharakov]

There are no "ifs" here, we are intelligent and birds are not. And there is a reason why it is so.

Putting on my best Jon Stewart aire: "Do go on". (six men in the background who have just finished tying the thirteen loop knot now advance on Barbos with glee in their eyes. One tells Jokodo to "please step aside")

Come on old man, don't feed Barbos crow!

Hehe... just heard one of the boogers caw outside. I love crows.

 

[Jokodo]

Except that, in the history of Earth alone, very different animals have occupied more or less in the same environments. Since the Cretacean, bony fish, and specifically  perciformes (an order that only arose in the late Cretacean and comprises 40% of all living fish species) have taken niches that where previously occupied by ammonites, and before them by trilobites.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

They are also moving along an evolutionary line while in similar environments.

Not necessarily - the trilobites fell victim to a mass extinction event that killed of some 95% of species at the time.

So we could assume that varying species are able to live in the same environment, but a similar evolutionary line might progress in a similar planet.

You're dangerously close to teleological thinking here.

Not really. What I mean is that given similar conditions, not only are similar life-forms going to come into existence, but it's also likely that they'll start in a similar place, and move in a similar direction.

For instance, life is more likely to start in water than on land, and assuming land exists, it should eventually move onto land with an amphibian like appearance, and so on.

That's not a guarantee that intelligent life arises, but it's very likely that intelligent life would arise eventually given the right circumstances, as intelligence seems to be a great driver in reproductive success.

What makes you think so? For approximately 99% of our history as a distinct line from the chimpanzee one, we've been outnumbered by baboon-like monkeys which were in turn outnumbered by springbok-like ungulates.

Humans != the only intelligent species

So? I'm pretty sure that herring outnumber dolphins in the oceans, and pigeons and sparrows crows in our cities.

 

[Jokodo]

The  Coconut crab can weigh up to 4.1kg - that's an order of magnitude above your typical squirrel.

I stand corrected. Still, that does seem to be the upper limit. Part of the reason why it seems to have been able to grow as big as it has is because of its lung, which is something most exoskeleton creatures lack.

Most* vertebrates, i.e. almost all fish also lack lungs.


*) In terms of number of species and individuals at least - in terms of biomass, our lifestock might be serious competitors.

 

[barbos]

Except that, in the history of Earth alone, very different animals have occupied more or less in the same environments. Since the Cretacean, bony fish, and specifically  perciformes (an order that only arose in the late Cretacean and comprises 40% of all living fish species) have taken niches that where previously occupied by ammonites, and before them by trilobites.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

They are also moving along an evolutionary line while in similar environments.

Not necessarily - the trilobites fell victim to a mass extinction event that killed of some 95% of species at the time.

So we could assume that varying species are able to live in the same environment, but a similar evolutionary line might progress in a similar planet.

You're dangerously close to teleological thinking here.

Not really. What I mean is that given similar conditions, not only are similar life-forms going to come into existence, but it's also likely that they'll start in a similar place, and move in a similar direction.

For instance, life is more likely to start in water than on land, and assuming land exists, it should eventually move onto land with an amphibian like appearance, and so on.

That's not a guarantee that intelligent life arises, but it's very likely that intelligent life would arise eventually given the right circumstances, as intelligence seems to be a great driver in reproductive success.

What makes you think so? For approximately 99% of our history as a distinct line from the chimpanzee one, we've been outnumbered by baboon-like monkeys which were in turn outnumbered by springbok-like ungulates.

Humans != the only intelligent species

For planet Earth they are.
Human intelligence is a result of evolution and it is not inevitable result.
There has been a lot of dumb luck in that process I think, otherwise we would have had multiple distant evolutionary paths ending in human like intelligence.
Some here may stubbornly disagree but only apes had all the necessary prerequisites to evolve into truly intelligent specie.
Birds don't have arms - very limited in tool usage,
Dolphins stuck in water - no fire - no technology.
And even with all prerequisites most apes are pretty happy where they are now and are not particularly interested in becoming super smart, at least for now. Human Intelligence is most likely very rare in the Universe.

- - - Updated - - -

So why haven't exoskeleton animals evolved that are much larger? Granted there can't be a land squid, but why isn't there an ant species as large as say a squirrel? I don't know anything in the laws of physics that would prohibit such. But maybe it is just very hard to build a large exoskeleton. I would think that overall the permutations are somewhat limited for the development of advanced lifeforms. I saw a biological commentary on Starwars and it made it clear that the creatures were too outlandish to evolve, in part because they had so many strange appendages. Too easy to take off and get one in trouble. But exoskeletons vs Chordate type structure?

SLD

I would imagine that as insects have evolved to be larger they would be more likely to be eaten.

When oxygen content in the air was 30% insects were much bigger.

 

[dystopian]

I stand corrected. Still, that does seem to be the upper limit. Part of the reason why it seems to have been able to grow as big as it has is because of its lung, which is something most exoskeleton creatures lack.

Most* vertebrates, i.e. almost all fish also lack lungs.

I'm not sure how this is relevant to how *large* land dwelling animals could become, though? Note that I'm not saying we couldn't conceivably have animals pretty different to the ones we currently have if evolution happened along slightly different lines. I'm just saying that for any given set of environmental conditions, there's going to be an optimum/likely range that evolution will tend to follow; and so unless Earth is anomalous in that regard, we should expect life that came about on a random but similar planet to our own to be pretty recognizable to us.

 

[Jokodo]

Except that, in the history of Earth alone, very different animals have occupied more or less in the same environments. Since the Cretacean, bony fish, and specifically  perciformes (an order that only arose in the late Cretacean and comprises 40% of all living fish species) have taken niches that where previously occupied by ammonites, and before them by trilobites.

as for intelligent life then too, I expect them to pretty much look like us - bi-pedal apes of roughly our size.

I seem to have a deja vu. Didn't we have this discussion before over on the old board? I seem to remember that you explicitly refused to provide any rational argument for your claim then.

They are also moving along an evolutionary line while in similar environments.

Not necessarily - the trilobites fell victim to a mass extinction event that killed of some 95% of species at the time.

So we could assume that varying species are able to live in the same environment, but a similar evolutionary line might progress in a similar planet.

You're dangerously close to teleological thinking here.

Not really. What I mean is that given similar conditions, not only are similar life-forms going to come into existence, but it's also likely that they'll start in a similar place, and move in a similar direction.

For instance, life is more likely to start in water than on land, and assuming land exists, it should eventually move onto land with an amphibian like appearance, and so on.

That's not a guarantee that intelligent life arises, but it's very likely that intelligent life would arise eventually given the right circumstances, as intelligence seems to be a great driver in reproductive success.

What makes you think so? For approximately 99% of our history as a distinct line from the chimpanzee one, we've been outnumbered by baboon-like monkeys which were in turn outnumbered by springbok-like ungulates.

Humans != the only intelligent species

For planet Earth they are.
Human intelligence is a result of evolution and it is not inevitable result.
There has been a lot of dumb luck in that process I think, otherwise we would have had multiple distant evolutionary paths ending in human like intelligence.
Some here may stubbornly disagree but only apes had all necessary prerequisites to become truly intelligent specie.
Birds don't have arms - very limited in tool usage,
Dolphins stuck in water - no fire - no technology.
And even with all prerequisites most apes are pretty happy where they are now and are not particularly interested in becoming super smart, at least for now. Human Intelligence is most likely very rare in the Universe.

I agree that human-like intelligence is likely rare in the universe. Where I disagree is that if and when it turns up, it will be particularly similar to us.
There's been a lot of dumb luck leading to our place is exactly my point. Even more, there's been a lot of dumb luck leading to the existence of dolphins, corvids, and apes. Even if it's true that among the (family-level) groups that existed on earth 10 Ma years ago, apes were the only group that had the prerequisites to become an intelligent, technological species, this doesn't generalise to other worlds - there probably wouldn't be anything we'd recognise as an ape there, but there might be other groups that just never happened to arise on Earth with similarly good prerequisites.


- - - Updated - - -

Most* vertebrates, i.e. almost all fish also lack lungs.

I'm not sure how this is relevant to how *large* land dwelling animals could become, though? Note that I'm not saying we couldn't conceivably have animals pretty different to the ones we currently have if evolution happened along slightly different lines. I'm just saying that for any given set of environmental conditions, there's going to be an optimum/likely range that evolution will tend to follow; and so unless Earth is anomalous in that regard, we should expect life that came about on a random but similar planet to our own to be pretty recognizable to us.

Recognisable as life? Sure. Recognisable as something we might almost mistake for a terran ape, or even just mammal? I bet not.

 

[Kharakov]

Alternate biochemistries?

Just reading up on  hypothetical types of biochemistry over at wikipedia. I looked up Silicon based life forms, although I recalled that there were various reasons that Silicon is not as suited for life as Carbon, and of course that wiki popped up.

 Organosilicon

Where is the terminus of biochemistry?