Convergent Evolution and Alien Life

Originally posted by Shadowed
Anyone familiar with Dr. Crick? I was a student of Biology and Dr. Crick paired with Dr. Watson were the first to recreate the beginnings of life in a controlled environment. It was a beautiuflly designed experiment.

Dr. Crick is the scientist who supports the theory that life on earth originated from elsewhere in the universe; i.e. Mars, asteroid, or comet colliding with earth, bringing with it organic life.

Perhaps you are thinking of Dr. Miller's experiment, which implies the "Primordial Soup" theory, that a certain mixture of the early earth atmosphere, coupled with an electronic shock from lightning, created the first organic life.

Unfortunately, this theory has been disproved because it was found that the atmospheric conditions in his experiment were not the same as the atmospheric conditions found on earth when life began.

It is a good idea though, and proves that life can essentially be "created" with the right ingredients.

Originally posted by Monts
Yes, I agree with you completely to think that its narrow-minded to think that all extra-terrestrial life must occur in environments like earth...

I don't think it is narrow-minded at all. After all, so far the evidence tells us that it does evolve on Earth-like planets and have yet to find it on a non-Earth-like world. Of course, we are working with only one data-point, so that could easily change.

I think whether or not life can develop on non-Earth-like worlds depends on whether or not panspermia is true. It would seem to me that if life developed independently on Earth, then it would mean life can develop in a variety of worlds. But if life were seeded here, directed or accidental, it may mean that life can only develop under certain conditions. Those same mechanisms that brought the building blocks of life to Earth would have brought them to other worlds in our solar system. Yet as far as we know, Earth is the only one to have developed life.

Originally posted by TrueBrit

Originally posted by Monts
Good Post

I've always thought, according to the traditional scientific view on the possibilities of extra-terrestrial life, that life on other planets would be quite similar to ours.

Seeing as how traditional science limits it's search possibilities to "Earth-like planets"; i.e. same distance from star, same type of star, same atmosphere, ect., it would only make sense that life would adapt to such a similar environment in the same way it adapted to Earth's environment.

Of course, as the article states, this wouldn't mean identical species, but simply similar evolutionary traits.

Surely you understand the need for "traditional" space science to evolve beyond looking for life we would recognise? There could be races of beings living in the gaseous expanse of jupiter that you and I would mistake for mere clouds, or silicone based lumps of rock that have the intelligence of a thousand einsteins living on Mars under the soil. We wouldnt know how to examine one for life signs, but whos to say there isnt life of an unrecognisable nature out there!? The scientists need to start thinking outside the miniscule little box they have been poking around in for the last god knows how long!

Searching for life that "we cannot recognize" is an utterly pointless pursuit.

How exactly would one go about looking for something unrecognizable?

Besides, we *do have* evidence that the life we recognize is a possibility, but have no evidence of other life forms beyond our recognition. Not saying they don't exist, just that, without evidence, there is no starting point for the search.

-rrr

Originally posted by Monts
Unfortunately, this theory has been disproved because it was found that the atmospheric conditions in his experiment were not the same as the atmospheric conditions found on earth when life began.

It is a good idea though, and proves that life can essentially be "created" with the right ingredients.

The primordial soup theory may be falling by the wayside based on current evidence but it does not mean life did not start here on Earth. It may have started in thermal-vents in the ocean.
80-Year Theory Of 'Primordial Soup' As The Origin Of Life Rejected By New Research

Today the 'soup' theory has been overturned in a pioneering paper in BioEssays which claims it was the Earth's chemical energy, from hydrothermal vents on the ocean floor, which kick-started early life.

Originally posted by ucalien

The usual arrogance of human being... What else could I say about the pathetic attempt of earthling scientists, to put an Earth-like standard to define other intelligent life forms among zillions of galaxies?? It's RIDICULOUS!!! It's just a silly way of handle with their fears. The fear of unknown, the fear of the different. "extraterrestrial life quite similar to ours"... WTF is that mean?? We evolved from primates, but just tell me what prevents intelligent beings evolving from felines, canines, insects, reptiles, amphibians or whatever??? Since a planet have environmental conditions to provide complex organisms and to increase their development to any possible biological direction, where's wrote in the "alien lifeforms handbook for dummies", that "intelligent lifeforms have to be similar to earthling humans"????

Um I dont think any of us have said anything like that, for me when I say 'Similar' i simply mean humanoid or near enough, and my deffinition of humanoid is fairly broad. If you showed me a bi/tri/quadrupedal slug like being with sense organs on its upper most point with 1 or more limbs used for tool manipulation id say its like us, simply because its basic form is similar, even in its exoticism. Saying they'd be human like doesnt preclude anything, heck we share our basic form with every other mammal on the planet, primate or not, along with lots of similarities in form with fish, birds (insects kinda push it)

No one here is fearful of anything.

And about what I said with ignoring the atmosphere of a planet, its just that for me, atmosphere in terms of breathing and how their blood system or its equivalent would work doesn't seem to be a huge impact, while if a planet is far to cold or hot, life as we'd recognize it just couldnt happen. Simply since the chemical processes that would give rise to that life wouldnt happen. Atmosphere can affect these environmental factors of course, but ultimately extreme temperature (which is what I meant by environment) would be a bigger factor. If the temp is right, regardless of the atmosphere, something should evolve that can take advantage of it.

I know this "if" is too big a hurdle for some people, if so ignore this post but otherwise if you accept some contact / sightings / abduction testimony then we probably have more than the one data point.

You have upright walking 4 limbed beings with eyes and a degree of intelligence that also seem able to exist unaided in earths atmosphere.

That suggests convergent evolution either by chance or design.

If by chance it also suggests that this may be the optimum arrangement for the evolution of intelligence in the absence of any reports of jellyfish or similar.

and just to add that in any discussion such as this I can't help but be reminded of Monty Python's The Galaxy Song so please indulge me as I post the lyrics, kind of on topic !

Whenever life gets you down, Mrs. Brown
And things seem hard or tough
And people are stupid, obnoxious or daft
And you feel that you've had quite eno-o-o-o-o-ough

Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour
That's orbiting at nineteen miles a second, so it's reckoned
A sun that is the source of all our power
The sun, and you and me, and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour
Of the galaxy we call the Milky Way

Our galaxy itself contains a hundred billion stars
It's a hundred thousand light-years side to side
It bulges in the middle sixteen thousand light-years thick
But out by us it's just three thousand light-years wide
We're thirty thousand light-years from Galactic Central Point
We go 'round every two hundred million years
And our galaxy is only one of millions of billions
In this amazing and expanding universe

The universe itself keeps on expanding and expanding
In all of the directions it can whiz
As fast as it can go, at the speed of light, you know
Twelve million miles a minute and that's the fastest speed thereis
So remember when you're feeling very small and insecure
How amazingly unlikely is your birth
And pray that there's intelligent life somewhere up in space
'Cause there's bugger all down here on Earth

I don't totally agree with his claims...we see similar trends with the life on Earth because every species evolved from one single organism...but even so, we see a vast array of different shapes, sizes and designs for the life on Earth...there are some really whacked out species...and also, the life on Earth is particularly designed to be highly effective and most efficient with Earths conditions...who knows how different their planet might be...scientists seem to have this silly mentality that life will only develop on planets quite similar to Earth...

But...I do partially agree that's it's very possible we will see similarities where nature has developed common solutions to common problems...but I doubt there would be any sort of remarkable resemblance...

If it's life in general, there are many forms existing native to this planet that seem quite alien. So who knows what form it would take? Convergent evolution does seem to show up a lot. Eyes and limbs are a good example, what works works. Also there are times where less likely things show up as well. There are even species of flys that fight for mates with modified antennae in the same manner deer do with antlers.

If you're talking about technological life, then this is what I'd expect in the way of convergent forms and behaviors:
Bilateral symetry. When it comes to known animals, this is the form that seems the most mobile within a reasonable size range.
Eyes with binocular vision. Good enough eyesight and depth perception.
Grasping limbs or appendages with fine motor control. May not be hands (tentacles, claws, or something like an elephant's trunk could work), but you're not going to be building anthing technical unless you can manipulate your environment with some degree of precision.
Apex predator or omnivore status. The species that hunt always seem to have to figure and evolve ways to outsmart the hunted. An apex species because smartest ones are going to be on top of the food chain. Herbivores don't seem as likely to need the same degree of intelligence because plants don't run away. For apex herbivores, it seems it's simply an easier survival strategy to get bigger than smarter.
Social species. It's easier to gather resources and survive through the hard times if you can pull together as a group. In the times that aren't so hard, this also means there's more free time and energy to develop technical progress.
A land dwelling species. You're not going to readily be able to harness fire and all the stuff that comes afterward if you're living underwater.

(It makes sense to go with the sames thing Michio Kaku mentions on this particular subject.)

Other than those including the above factors, who knows what form it'll take. If not resembling mammals, then birds, reptiles, arthropods, or even things that look like higher mollusks (gastropods or cephalopods) seem just as likely.

reply to post by BigfootNZ

number of fossils from a small number of sites around the world. yet attempt to paint a broad picture of prehistory of the globe. The only way you could be totally sure is if you scoured every inch of the surface of the earth, which just isnt going to happen.

i cant prove a negative, its up to you to provide evidence of your theory. As of 2010 no paleontologist has any evidence of a previous civilization on earth. Finding the lineage that species evolved from would be a start.

if there was evidence it would change evrything i wouldnt be saying tech intelligence is rare. It would be obvious that tech intelligence is a convergent feature. So far no evidence of that.

As for brain size to intelligence that is a rather out dated concept

brain to body mass ratio is crude and overused but is still accurate as a rule of thumb. So no its not outdated.



[edit on 9-2-2010 by yeti101]

reply to post by Springer


kepler will tell us size & orbit not if theyre habitable.

reply to post by DoomsdayRex


if tech intelligence is inevitable on any planet with complex life the proponents of that idea need to have a good answer to the fermi paradox. Otherwise its just wishfull thinking.

Assumption is the mother of all...... errors.

We only have one reference point.

Pure speculation.

Originally posted by yeti101
if tech intelligence is inevitable on any planet with complex life the proponents of that idea need to have a good answer to the fermi paradox. Otherwise its just wishfull thinking.

Not necessarily. You are missing some operative caveats in my question, on planets were it is allowed to thrive and given long enough. There are planetary and cosmological catastrophes that can stunt the evolutionary process or wipe out life on a world. It's happened on Earth at least five times before. I think life in general may be rare in the galaxy but intelligent life those worlds not be.

I think there are two great answers to the Fermi Paradox. One is the Great Filter; some mechanism is preventing most intelligences from either leaving their planet or colonizing the galaxy. The implications don't bode well for us.

Another answer is that the Fermi Paradox needs a caveat attached. It's not that we don't see evidence of advanced intelligences, it's that we don't see evidence for them yet. While there have been searches for cosmic-level engineering projects, those searches have not been exhaustive. And we've just started searching. We may not yet recognize these projects for what they are. Seth Shostak argues that advanced civilizations may not even be engaging in such projects.

reply to post by DoomsdayRex



Great thread OP, one of the subjects I really like to explore.

Evolution moving to similar forms in similar enviroments is well known. Shark=Ichthyosaur=Dolphin, A fish, Reptile and Mammel with basically the same body plan because they live(d) in the same enviroment, filling the same niche. Now lets look at Humans, we show some of our hubris by calling our general body plan "Humanoid" but lets stretch this a bit...

Would Birds be considered "Humanoid"? they are bipedal...
How about Bears and some reptiles? They to can assume a bipedal stance...
How about our kin? Apes, Lemurs etc. are they Humanoid too?

If you say more or less "yes" then you would have to say our Humanoid body plan is not uncommon, basically any land dwelling life form that evolves to free up a set limbs to be manipulators might fall into the Humanoid stance as well.

The trick part is we don't know what form dna and evolution will push a life form outside of Earths conditions.

Is the Humanoid form a good shape on a Earth with 1.5 times Earth gravity? how about 2x?

How about .5?

What happens when there is no moon? What happens when there are lots of moons?

Even the slightest difference in planetary conditions could send life down wildly different paths then those here at home.

That being said, if we find other "techies" out among the stars I think we can only be sure they will have sensors (Eyes, Sonar, radar, lazers) and manipulators of some sort. The arrangement of the body plan though may be totally unique.

What will be even more fun is figuring out how to communicate with them. Lets say they have visual processing similar to an Earth cat. When we stream them video it may look like a flip picture book to them, what if their verbal mode is Ultrasound? What if the sound came out of a speaker arrangement instead of a mouth? How would we react to alien verbal and facial signals? What if they smiled when sad and farted when angry?

Lots of interesting things to consider.



[edit on 9-2-2010 by Helmkat]

reply to post by DoomsdayRex


yeah there could be a filter. But thats quite depressing tbh as you said it doesnt bode well for us.

i'm more optimistic i think were already past the filter. The filter being nature just doesn't produce tech intelligence very often.

[edit on 9-2-2010 by yeti101]

Originally posted by TrueBrit

Originally posted by Monts
Good Post

I've always thought, according to the traditional scientific view on the possibilities of extra-terrestrial life, that life on other planets would be quite similar to ours.

Seeing as how traditional science limits it's search possibilities to "Earth-like planets"; i.e. same distance from star, same type of star, same atmosphere, ect., it would only make sense that life would adapt to such a similar environment in the same way it adapted to Earth's environment.

Of course, as the article states, this wouldn't mean identical species, but simply similar evolutionary traits.

Surely you understand the need for "traditional" space science to evolve beyond looking for life we would recognise? There could be races of beings living in the gaseous expanse of jupiter that you and I would mistake for mere clouds, or silicone based lumps of rock that have the intelligence of a thousand einsteins living on Mars under the soil. We wouldnt know how to examine one for life signs, but whos to say there isnt life of an unrecognisable nature out there!? The scientists need to start thinking outside the miniscule little box they have been poking around in for the last god knows how long!

Evolution MUST have a purpose. Why would the mechanism that directs the evolution process of a life form choose as the pinnacle of of its evolution a creature resembling a lump of rock? An intelligent lump of rock anyway.
Why shouldn't Evolution itself be some kind of projection or even some kind of evidence of an intelligence of something we don't understand? It wouldn't be too intelligent if it had decided to condemn its own offspring as lumps of rock in a barren landscape.
I mean what would be the point?
Where could they go from there?

Gaseous forms would be something else though. Yet again why life would have to choose for itself to evolve to a gaseous form? To be predatory? Again how much would it had survived from other more successful predators out there?
Why shouldn't life be choosing a biped growing in a small planet like ours for the best candidate of evolution?
We can clearly see what points it did have, in creating us and they were successful.

[edit on 9-2-2010 by spacebot]

Science is not narrow minded.
Scientists search our solar system and they didn't find larger evidence of life in our gaseous planets, or in our inner hot melting rocky planets, neither at our sun. They did at earth of course and possibly Mars.
It is logical after all to assume that similar conditions have good chances to be the norm out there.

[edit on 9-2-2010 by spacebot]

Great post OP!

First and foremost, let me expand on the Goldilocks Zone that has been mentioned before. As for our planet Earth it lies at one A.U. (149,597,871 kilometers). We are fortunate to be lying in this vicinity of a G-type main sequence star (Yellow Dwarf). I think we are very fortunate to be lying in this orbit, as Venus (almost the same size) did not fare well. On the other side we have Mars, it is smaller but just big enough to hold an atmosphere. So why no life there? I will use this quote from a New Scientist article to explain what might have happened on Mars:

"It is easy to picture a planet without oxygen. It looks like Mars. Our nearest planetary neighbor was probably once a water world too, primed for life to evolve. But it lacked a vital ingredient: a protective shield of ozone derived from oxygen. Without an ozone layer, the sun's rays slowly atomised the Martian water. The hydrogen floated off into space while the oxygen oxidised the iron-rich Martian topsoil, turning it rust-red. Perhaps there is - or was - life on Mars. But if so it never progressed beyond the bacterial stage."

But we could have many permutations of what a "hospitable" environment can become. Let's say for instance an Earth sized planet revolving around a super-giant sun but at a distance that would allow water to flow (and not evaporate) and perhaps let life go forth. Would sentient life have enough time to evolve to be self-conscious?
Or how about this scenario? A red dwarf with a closely orbiting 2x Earth-sized planet that would allow water to flow. Water is a VERY versatile solvent that does many things. Would it allow life to grow there?
We must not forget DNA. Oh yes, Deoxyribonucleic acid. It is a fascinating structure. One that permits many biochemical instructions to be realized. Even back six years ago, scientists even came up with alternate DNA encoding:

www.spacedaily.com...

My point is that life could have originated in both extremes and in different DNA permutations. As for convergent evolution we can only study our own reference point, and that is Earth.
For now I think we are unique and we got here by accident. Of the millions and millions of years dinosaur evolution, nothing sentient came about from their evolutionary line only tells me that we are lucky to be here. After they died off, we got lucky and even luckier if we found omega 3 fatty acids to add to our diet.
But let me digress a bit. I would also like to mention that oxygen is the waste byproduct of ancient and current bacteria. Dinosaurs grew to their tremendous sizes because they lived during a period of great oxygen levels.
And there is the GAIA effect that trees and forests are growing bigger and faster:

www.livescience.com...

Perhaps, the whole Earth is a sentient being. I can attest to this as I have been through jungles of the equatorian region and I have seen amazing co-existent and symbiotic organisms working with each other.
This is why we must save the rainforests. They are there as a "buffer zone".

At this point all I can say is save the rainforest..they are our lungs....

reply to post by TrueBrit


Your using a theory in which anything could be anything. While the statement does hold mostly true you have to think why intelligence would settle with being a gas cloud... or a rock under mars surface.

Intelligence is defined as: the ability to comprehend; to understand and profit from experience.
This means that intelligent life would naturally want progression, or they are not intelligent. A progressive being would have to be one that can actually progress. Bacteria is identifyable because it is progressive so i very much doubt alien life wouldnt be this idea of 'progressive'.

reply to post by Kratos40


But the fact that we have found martian life in the form of insects (wonder why it wasnt gobally recognised, but some papers covered it) throws the whole new scientist mars theory off.

[edit on 10-2-2010 by Encoded05]