granpa

interstellar dust grains/living molecules

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could some of the interstellar dust grains (is that the right word) be living self reproducing molecules perhaps similar to (very primitive) ribosomes?

 

if it was just a single self-replicating ribozyme-like molecule then

there would be no need for water.

Water is the 'medium' in which life processes occur on earth.

In space, space itself would be the 'medium'.

 

If these molecules seeded earth with life (or at least with organic molecules) by means of comets

then maybe they have seeded all habitable planets in this galaxy.

If so then life must be everywhere.

 

This does just move the "how did it start" question somewhere else,

but it moves it to the vast molecular clouds of interstellar space where

there are far more oportunities for just the right molecules to come together in just the right way.

 

 

vertebrates, arthropods, & molluscs correspond to the 3 modes of moving used by worms:wriggling, walking, & sliding.

This is suficiently basic that I would assume that it would evolve on any planet.

 

trilobites

lobsters

 

Arthropod bodies are naturally waterproof so

they would tend to be the first to leave the ocean and colonize land on any planet.

first land animal (millipede)

Although myriapods clearly evolved from aquatic ancestors, there is no clear candidate known.

scorpions and spiders

insects

 

I think social insects (termites, wasps, ants) are most likely to develop higher intelligence first.

The idea that their bodies would be too heavy to grow large is bunk.

(edit:Yes there is a limit to how big they can get but

I see no reason to suppose they cant get nearly as big as a human)

 

After all , if a vertebrate can get as large as this:

380px-Longest_dinosaurs1.png

then is it really so surprising to suppose that an insect might be able to get nearly as large as a human?

(and that dinosaur had one hell of a big ribcage and its leg bones were probably nearly as large as its legs)

 

And these guys here were not plodding:

300px-Largesttheropods.png

 

So why did insects never get so big.

I'm thinking that they didnt get big for the same reason

that mammals didnt get big during the time of the dinosaurs.

There was already a very big predator. (centipedes and maybe millipedes)

It stands to reason that centipedes can always get much larger than a 6 legged insect.

 

 

Intelligent life:

It took 5 billion years for intelligent life to evolve on earth but

the milky way galaxy is over twice that age.

Furthermore, once one species on a planet becomes advanced enough to

genetically engineer animals and they figure out how brains function then

it may only be a short time before

nearly all large animals on that planet are intelligent.

 

Superintelligent life:

I suspect that ecosystems derived from extremely high tech terraforming nanobots are not rare.

They may even be the rule rather than the exception.

Over time they would eventually evolve into some very impressive highly intelligent half-robot half-animal creatures.

 

Origin of the universe:

Edited by granpa

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Did you read about the recent discovery of sugar absorption lines in space?

 

What that implies is that something produced that sugar, a living orgaisim maybe?

 

The probably with confirming or denying any of these things is we look for things that living things on earth do (produce sugar), but that might not be the only kind of "life" out there...

 

As for your comet comment, there's been alot of talk about that kind of thing in recent years, it of course just moves the "but how did it start" question somewhere else, it doesn't get rid of it.

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Yes it does just move the "how did it start" question somewhere else,

but it moves it to the vast molecular clouds of interstellar space where

there are far more oportunities for just the right molecules to come together in just the right way.

 

if it was just a single self-replicating ribozyme-like molecule then

there would be no need for water.

Water is the 'medium' in which life processes occur on earth.

In space, space itself would be the 'medium'.

 

If these molecules seeded earth with life (or at least with organic molecules) by means of comets

then maybe they have seeded all habitable planets in this galaxy.

If so then life must be everywhere.

 

It took 5 billion years for intelligent life to evolve on earth and

the milky way galaxy is over twice that age.

 

Once one species on a planet becomes advanced enough to

genetically engineer animals and they figure out how brains function then

it may only be a short time before

nearly all large animals on that planet are intelligent.

 

Dr. Ian Malcolm:

If there is one thing the history of evolution has taught us it's that life will not be contained.

Life breaks free, expands to new territory, and crashes through barriers

 

Yeah, i just quoted a hollywood movie. So sue me.

Edited by granpa

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vertebrates, arthropods, & molluscs correspond to the 3 modes of moving used by worms:wriggling, walking, & sliding.

This is suficiently basic that I would assume that it would evolve on any planet.

 

trilobites

lobsters

 

Arthropod bodies are naturally waterproof so

they would tend to be the first to leave the ocean and colonize land on any planet.

first land animal (millipede)

millipedes

Although myriapods clearly evolved from aquatic ancestors, there is no clear candidate known.

insects

scorpions and spiders

I think social insects (termites, wasps, ants) are most likely to develop higher intelligence first.

The idea that their bodies would be too heavy to grow large is bunk.

Look at your own ribcage and skull.

If anything insect bodies would be lighter.

(edit:Yes there is a limit to how big they can get but

I see no reason to suppose they cant get nearly as big as a human)

 

I suspect that ecosystems derived from extremely high tech terraforming nanobots are not rare.

They may even be the rule rather than the exception.

Over time they would eventually evolve into some very impressive highly intelligent half-robot half-animal creatures.

Edited by granpa

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Arthropod bodies are naturally waterproof so

they would tend to be the first to colonize land on any planet.

I think social insects are most likely to develop higher intelligence first.

The idea that their bodies would be too heavy to grow large is bunk.

Look at your own ribcage and skull.

If anything insect bodies would be lighter.

 

I suspect that ecosystems derived from extremely high tech terraforming nanobots are not rare.

They may even be the rule rather than the exception.

Over time they would eventually evolve into some very impressive highly intelligent half-robot half-animal creatures.

 

http://en.wikipedia.org/wiki/PAH_world_hypothesis

http://www.abc.net.au/science/news/stories/s603155.htm

 

vertebrates, arthropods, & molluscs correspond to the 3 modes of moving used by worms:wriggling, walking, & sliding.

This is suficiently basic that I would assume that it would evolve on any planet.

 

 

So the cube square law is bunk? There are clear evolutionary pathways from soft bodied worms to hard bodied arthropods. Arthropods did not colonize the earth, if anything did it was something like Archaea, but I see no reason to assume life did not start right here on the Earth.

Edited by Moontanman

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So the cube square law is bunk? There are clear evolutionary pathways from soft bodied worms to hard bodied arthropods. Arthropods did not colonize the earth, if anything did it was something like Archaea, but I see no reason to assume life did not start right here on the Earth.

 

what on earth are you talking about.

 

 

first off I didnt say arthropods colonized the earth. I said arthropods were the first to colonize the land.

 

second I said that it is bunk that insects cant grow as large as humans. (or at least large enough to hold a large brain)

If their exoskeleton would be too big then why isnt our ribcage and skull too big for us to evolve?

 

I think life did evolve on earth from organic molecules deposited from comets produced by living molecules in space. The molecules though alive in space could not survive in such a radically different environment as the earths primitive ocean.

Edited by granpa

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what on earth are you talking about.

 

I am sorry i misunderstood.

 

first off I didnt say arthropods colonized the earth. I said arthropods were the first to colonize the land.

 

Yes you are almost certainly correct.

 

second I said that it is bunk that insects cant grow as large as humans. (or at least large enough to hold a large brain)

 

Then why didn't they? They had many times as much time as vertebrates did to do so... Arthopods due to several things not the least of which is the cube square law, cannot reach the size of vertebrates and remain as active as vertebrates can.

 

 

largest land arthopod the coconut crab

 

coconut-crab.jpg?w=450&h=337

 

 

It's big but very clumsy and vertebrates are quickly driving them to extinction...

 

If their exoskeleton would be too big then why isnt our ribcage and skull too big for us to evolve?

 

Um because it's internal and not external? Your skull is not a supporting part of your body, it only has to hold the brain.

 

Athopods have been around for many millions of year longer than vertebrates but we have hogged all the large animal spots for ourselves. Lower gravity and higher oxygen content and you might get large exoskeleton animals but not on the Earth...

 

Social insects have been around far longer than vertebrates but not even fire has been "discovered" by social insects despite over a hundred million years of social living.

 

I think life did evolve on earth from organic molecules deposited from comets produced by living molecules in space. The molecules though alive in space could not survive in such a radically different environment as the earths primitive ocean.

 

It's quite possible that such a scenario was helpful to the development of life on the earth...

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Um because it's internal and not external? Your skull is not a supporting part of your body, it only has to hold the brain.

 

Pardon me but it is external in the sense that it is just below the skin.

(As opposed to our arm and leg bones which are in the very center)

The ribcage and skull may not support weight but they are still big and heavy

(to protect the organs inside)

Anyway, external skeletons are actually more efficient at supporting weight.

A tube gets stronger as it gets larger.

 

I think that molting is probably the limiting factor in the size of insects.

Thats not a problem for social insects

so I see no reason they couldnt grow very large as larvae

then pupate into near human sized animals.

 

Unfortunately social insects didnt evolve until long after dinosaurs took over.

 

coconut crabs may be clumsy but then so are alligators.

Crabs are sea creatures anyway.

If we are going to talk about sea creatures then how about eurypterids?

http://en.wikipedia.org/wiki/Eurypterid

 

the largest land arthropod ever was the millipede Arthropleura

http://en.wikipedia.org/wiki/Arthropleura

It is also thought that Arthropleura was capable of traveling under water,

and that it may have returned to lakes and rivers in order to molt its shell.

This would have made it vulnerable to attack by large fish and amphibians.

On land an adult Arthropleura would have had few enemies.

 

But Insects are the arthropods that evolved specifically to live on, and move quickly and efficiently over, land.

I wonder what the largest insect ever was?

Looks like it was a dragonfly.

http://en.wikipedia.org/wiki/Meganeura_monyi

 

the largest today is a beetle (which also flies)

http://en.wikipedia.org/wiki/Goliathus

 

odd that flying insects get so big but walking insects dont.

I think you are right.

There has to be a reason that they didnt get large.

I'm just not convinced that its because their exoskeleton would have been too heavy.

I'll give it some more thought. (something to do with their lungs maybe)

 

edit:I'm thinking that they didnt get big for the same reason

that mammals didnt get big during the time of the dinosaurs.

There was already a very big predator. (centipedes and maybe millipedes)

It stands to reason that centipedes can always get much larger than a 6 legged insect.

 

 

edit:http://en.wikipedia.org/wiki/Giant_weta

Edited by granpa

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You can pack far more muscle on the outside of a bone than you can inside a tube, think if our bones were on the outside of our bodies, the tubes would be very thin, if the tubes were thick enough to hold all the muscle they would have to be much heavier.

 

You are correct in that one of the reasons for 28" dragon flies was oxygen, during the time of their lives the oxygen levels were thought to be close to 33% and a higher atmospheric pressure as well. Arthropods cannot compete on a one for one basis with vertebrates, vertebrates cleared the land of large arthropods due to being much stronger and due to better breathing apparatus but even if the breathing was equal vertebrates would still win due to the stronger bones and bigger muscles.

 

Some insects by the way do actively breath, wasps do for sure as do other very active insects. The giant crab i showed in an earlier post is going extinct because it cannot compete with rats, it's much bigger than rats but the rats are winning...

 

Giant flying insects were probably doomed by flying vertebrates as well, big insects are easy prey for mammals and reptiles. The big centipedes and millipedes died out too as vertebrates took over the land, they just can't compete but insects should have been able to compete with the big centipedes and millipedes, they certainly do now.

 

Now if vertebrates hadn't evolved, and they didn't have to, we might have very large arthropods, I'm betting no where near as big as vertebrates, but they wouldn't be able to compete with modern vertebrates if exposed to them, a tiny shrew can catch and over power insects much larger than it's self. vertebrates rule do to inherent superiority of internal skeletons...

 

Having said that, i have to admit a major overhaul of arthropod body plans might allow relatively large arthropods but it would be difficult to say how big but they wouldn't resemble what we think of as arthropods very much i bet...

 

BTW the largest insect in the world is the giant cricket... actually most of the really big insects are all close to the same size...

 

Deinacrida heteracantha, also known as the Little Barrier Island giant weta, is a species of insect in family Stenopelmatidae that has no wings. It is endemic to New Zealand.
Edited by Moontanman

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You can pack far more muscle on the outside of a bone than you can inside a tube,

think if our bones were on the outside of our bodies, the tubes would be very thin,

if the tubes were thick enough to hold all the muscle they would have to be much heavier.

 

we seem to be talking past one another.

I will accept, on your authority, that there might be a little truth to what you say

but I do not believe that it would prevent insects from being able to be large enough to have large brains.

I also accept that we are never going to see eye to eye on this.

 

 

insects should have been able to compete with the big centipedes and millipedes, they certainly do now.

 

(When I say that the insects couldnt have competed with the centipedes

I dont mean that they would be driven to extinction by centipedes but rather

that the insects would be prevented from evolving large size by them

just as dinosaurs prevented mammals from evolving large size during the time of the dinosaurs)

 

Why? Were mammals able to compete with dinosaurs?

centipedes and millipedes in those days were much larger than they are today.

one millipede was 8.5 feet long. Thats bigger than you.

if centipedes and millipedes were as large today as they were then then

there is no reason to suppose that insects would be able to compete with them.

Moreover, it stands to reason that a centipede with its many legs

will always be able to grow much larger than an insect with only 6 legs.

 

 

 

edit:

Euphoberia, which lived 300 million years ago, is the largest centipede at record, growing up to 39 inches in length. It lived alongside the largest land invertebrate ever: Arthropleura, a close relative of the centipede.

 

The largest living centipede, Scolopendra gigantea, has a toxic, extremely intense bite that's been likened to a gunshot wound or broken bone. It can induce anaphylactic shock in those allergic to bee stings and has been known to kill small children on very rare occasions. If a much larger centipede, like Euphoberia, were to have survived from prehistory, its venom might have the potential to kill a full-grown man.

Edited by granpa

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If a vertebrate can get as large as this:

380px-Longest_dinosaurs1.png

then is it really so surprising to suppose that an insect might be able to get nearly as large as a human?

(and that dinosaur had one hell of a big ribcage and its leg bones were probably nearly as large as its legs)

 

 

 

And these guys here were not plodding:

300px-Largesttheropods.png

http://en.wikipedia.org/wiki/Spinosaurus

http://en.wikipedia.org/wiki/Tyrannosaurus

Edited by granpa

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second I said that it is bunk that insects cant grow as large as humans. (or at least large enough to hold a large brain)

If their exoskeleton would be too big then why isnt our ribcage and skull too big for us to evolve?

 

Yeah? Try shedding your skeleton (~14% of your body weight) every time you grow a bit, then regrowing it without ending up looking like a deformed mass of jelly or getting eaten while helpless. An internal skeleton is really useful for big creatures, since it is alive and can grow as needed and doesn't leave you deliciously helpless every so often.

 

As for the scaling issues, read this:

http://fathom.lib.uchicago.edu/2/21701757/

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thats why I stated in post 8

I think that molting is probably the limiting factor in the size of insects.

Thats not a problem for social insects

so I see no reason they couldnt grow very large as larvae

then pupate into near human sized animals.

 

its also why I quoted

http://en.wikipedia.org/wiki/Arthropleura

It is also thought that Arthropleura was capable of traveling under water,

and that it may have returned to lakes and rivers in order to molt its shell.

This would have made it vulnerable to attack by large fish and amphibians.

On land an adult Arthropleura would have had few enemies.

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thats why I stated in post 8

 

 

its also why I quoted

http://en.wikipedia.org/wiki/Arthropleura

 

 

From your own link

What Arthropleura ate is a matter of debate among scientists, as none of the fossils have the mouth preserved. However, it is reasonably certain that it would have had a sharp and powerful set of jaws. Based on this assumption, it used to be thought that Arthropleura was carnivorous, but recently discovered fossils have been found with pteridophyte spores in the gut and in associated coprolites[1], suggesting that the creature ate plants.

 

they were plant eaters so they shouldn'have stopped insects from getting larger. oxygen would have been the biggest problem.

 

 

Moontanman, on 25 September 2010 - 07:24 PM, said:

 

insects should have been able to compete with the big centipedes and millipedes, they certainly do now. the giant centipede was a plant eater not a carnvore....

 

 

 

Arthropleura evolved from crustacean-like ancestors earlier in the Carboniferous, and was able to grow larger than modern arthropods, partly because of the high percentage of oxygen in Earth's atmosphere at that time, and because of the lack of large terrestrial vertebrate predators. Fossil tracks of an arthropod dating back to the Silurian are sometimes attributed to either Arthropleura, or a Silurian- to Early-Devonian millipede called Eoarthropleura. Arthropleura became extinct at the start of the Permian period, when the moist climate began drying out, destroying the rainforests of the Carboniferous, and allowing the desertification characteristic of the Permian. Because of this, oxygen levels in the atmosphere began to decline to more modest levels. None of the giant arthropods could survive the new dry, lower-oxygen climate. Its tracks have the ichnotaxon name Diplichnites cuithensis [2]

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As everyone knows

millipedes are for the most part herbivorous.

centipedes, which evolved 10 million years after millipedes, are carnivorous.

 

 

http://en.wikipedia.org/wiki/Millipede#Diet

Most millipedes are herbivorous, and feed on decomposing vegetation or organic matter mixed with soil. A few species are omnivorous or carnivorous, and may prey on small arthropods, such as insects and centipedes, or on earthworms. Some species have piercing mouthparts that allow them to feed on plant juices.

 

The digestive tract is a simple tube with two pairs of salivary glands to help digest the food. Many millipedes moisten their food with saliva before eating it.[4]

 

 

http://en.wikipedia.org/wiki/Centipede

Centipedes are a predominantly carnivorous taxon...Centipedes are among the largest terrestrial invertebrate predators and often contribute significantly to the invertebrate predatory biomass in terrestrial ecosystems...Scolopendra gigantea, also known as the Amazonian giant centipede, is the largest existing species of centipede in the world, reaching over 30 cm (12 in) in length. It is known to eat lizards, frogs, birds, mice, and even bats, catching them in midflight,[7] as well as rodents and spiders. The now extinct Euphoberia was the largest centipede, growing up to 1 m (39 in) in length.

 

From your own link

What Arthropleura ate is a matter of debate among scientists, as none of the fossils have the mouth preserved. However, it is reasonably certain that it would have had a sharp and powerful set of jaws. Based on this assumption, it used to be thought that Arthropleura was carnivorous, but recently discovered fossils have been found with pteridophyte spores in the gut and in associated coprolites[1], suggesting that the creature ate plants.

 

they were plant eaters so they shouldn'have stopped insects from getting larger.

 

Arthropleura was a millipede. Arthropleura could have been omnivorous.

I gave Arthropleura (a millipede) as an example of how big myriapods (millipedes and centipedes) got at that time.

At that time, I would have liked to have given a link to a giant prehistoric centipede but at that time I didnt know of any.

if you go back and look at what I actually wrote (rather than spending all your time trying to trip me up)

then you will see that I always carefully and deliberately stated 'millipedes and centipedes'.

 

 

Here is an example of a prehistoric giant centipede:

http://animal.discovery.com/tv/lost-tapes/death-crawler/

Euphoberia, which lived 300 million years ago, is the largest centipede at record, growing up to 39 inches in length. It lived alongside the largest land invertebrate ever: Arthropleura, a close relative of the centipede.

 

The largest living centipede, Scolopendra gigantea, has a toxic, extremely intense bite that's been likened to a gunshot wound or broken bone. It can induce anaphylactic shock in those allergic to bee stings and has been known to kill small children on very rare occasions. If a much larger centipede, like Euphoberia, were to have survived from prehistory, its venom might have the potential to kill a full-grown man.

Edited by granpa

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As everyone knows

millipedes are for the most part herbivorous.

centipedes, which evolved 10 million years after millipedes, are carnivorous.

 

 

http://en.wikipedia.org/wiki/Millipede#Diet

 

Arthropleura could therefore have been omnivorous.

 

http://en.wikipedia.org/wiki/Centipede

 

 

http://animal.discovery.com/tv/lost-tapes/death-crawler/

 

 

if you go back and look at what I actually wrote (rather than spending all your time trying to trip me up)

then you will see that I always carefully and deliberately stated 'millipedes and centipedes'.

At that time, I would have liked to have given a link to a giant prehistoric centipede but at that time I didnt know of any.

 

 

I'm not trying to trip you up, my quote was from your own link and it specifically said that the ancient giant centipede was a herbivore, it also confirmed that oxygen was a big factor. Tripping you up is not how this works, i thought you wanted to discuss the possibility of large arthropods not play games of one up manship. if you want to discuss the possibility of large arthropods a new thread should be started as this is off topic in this thread ...

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it specifically said that the ancient giant centipede was a herbivore

the article you quoted was about Arthropleura.

Arthropleura is a millipede.

I gave it as an example of how big myriapods (millipedes and centipedes) got at that time.

(And as an example of how big land arthropods can get)

It may well have been omnivorous. We simply dont know.

I would have liked to have given a link to a giant prehistoric centipede but at that time I didnt know of any.

 

 

Euphoberia is the giant centipede and it was carnivorous and poisonous.

There are no centipedes today that get anywhere near as large as Euphoberia.

There is no reason to suppose that if centipedes were that big today that

insects would be able to compete with them.

(I dont mean that they would be driven to extinction by centipedes but rather

that the insects would be prevented from evolving large size by them

just as dinosaurs kept mammals from evolving large size during the time of the dinosaurs)

 

I think the giant centipedes prevented insects from evolving large size during the time they existed.

Today of course vertebrates keep both insects and centipedes from evolving large size.

If insects had evolved a way to out-compete centipedes

(as mammals eventually found a way to out-compete dinosaurs)

then maybe they would have grown as large as humans.

 

 

The cube square law is certainly true.

There is a size that insects cant grow beyond.

I never said otherwise.

I just said that I dont believe that that size limit is as small as it is commonly thought.

I see no reason to suppose that insects couldnt grow nearly as large as humans.

(If vertebrates with big heavy ribcages and skulls can grow to the size of dinosaurs then

I see no reason why the idea of a nearly human sized insect should be so shocking)

If so then there is no reason they couldnt evolve large brains.

Molting would be an issue but not so much for social insects.

I see no reason social insects couldnt grow very large as larvae

then pupate into near human sized animals.

 

vertebrates, arthropods, & molluscs correspond to the 3 modes of moving used by worms:wriggling, walking, & sliding.

This is suficiently basic that I would assume that it would evolve on any planet.

 

Since arthropods are generally going to be the first to leave the ocean and

colonize land on any planet then I suspect that most alien species will turn out to be insects (especially social insects).

Edited by granpa

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