# Fish may have evolved to live on land more than 30 times



## Brian G Turner (Jun 18, 2016)

The idea of a single ancestor for all land animals may need serious revision:
http://www.sciencemag.org/news/2016/06/fish-may-have-evolved-live-land-more-30-times

Not only did the researchers discover at least 33 families of fish that evolved the ability to travel on land - some even appear to have evolved this ability multiple times.


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## Ray McCarthy (Jun 18, 2016)

Brian Turner said:


> The idea of a single ancestor for all land animals


Was that EVER seriously believed / proven or just a crackpot idea?


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## J Riff (Jun 18, 2016)

I remember being a diatom, then life got complicated. I blame radiation, Ray, wattayasay, hey, let's all evolve into 3 million species and see what happens. *


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## BAYLOR (Jun 18, 2016)

30 times ?Wow .


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## Silver Bee (Jun 18, 2016)

It's quite interesting to see that we tend to feel more comfortable with the idea that things and events should be unique for them to be 'true(er)': common ancestor, one true god, just one intelligent species, only planet with life on it, etc.
You read articles like this and end up thinking that multiplicity makes much more sense. I wonder if there could be more than one Mitochondrial Eve too!
Thanks for sharing


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## hopewrites (Jun 19, 2016)

Bee I think you've hit it on the head. Not just about how life evolved, but about how life happens. How many times do we sit down and think "gee, wouldn't it be great if I only had to write this award winning internationally best selling novel once, instead of slogging through all these tedious rewrites, and rejection letters, and under-performing sales?"

I know I'm guilty of expecting perfection from myself first go round, not even wanting to sit through my own montage... Haha. 
No.
It's never happened.

Good things take time and many starts, not all of them as false as they might appear in the short run.


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## Silver Bee (Jun 19, 2016)

Very interesting idea you brought up there, Hope: one big lucky strike as opposed to years (or centuries, or millenia!) of hard work.

It's fascinating to think there could have been multiple origins of life, although by the look of things, every form of life sharing the same genetic code and due to some biochemistry stuff that I won't even pretend I understand, only one of those succeeded.  Alternative biochemistry makes for a very nice Sci-Fi theme anyway 

Let's throw in a Frank Herbert quote: "The singular multiplicity of this universe draws my deepest attention. It is a thing of ultimate beauty"


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## Vertigo (Jun 19, 2016)

I think the evidence for a single origin is incredibly strong. But to my mind that only increases the wonder that we could end up with so much diversity of life, including multiple transitions from water to land, all from a single origin.


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## hopewrites (Jun 20, 2016)

I am probably ignorant of some important piece of information which negates my thought, but wouldn't adaptation cover multiple origin thingys?

People in different regions of the planet, with access to different grain, meat foodstuffs each come up with a way to package one food inside theother. I doubt there was a culinary meating between these people's, but believe that all felt that adapting food for travel was a good idea. That each people came up with the most palatable and feasible method for this adaptation.

I understand that the connection between steambuns and hotpockets is not completely comparable to the origins of life on this sphere... but it roughly covers my thought that all these originating lifes had to adapt to things that likely steered them in directions that brought them closer and perhaps even made them more compatible with each other. Fusion cuisine = cross breads?


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## Dave (Jun 20, 2016)

Victorian historians believed that all world history had been a natural progression from uncivilised barbarians towards their perfect society. In such a climate, it was also inconceivable that the ultimate aim of evolution was not to create Man, the ultimate creature made in God's image. Hence they had diagrams with Man at the top. Now that we known that none of that is true, there is no ultimate goal of either history or evolution. So, it isn't really that surprising that parallel evolution occurred wherever the habitat produced an ecological niche to be exploited. 30 times seems a lot but fish have been around a long time, so it sounds about right.

It does however ask the question the Hopewrites is making - how many times did life start and fail before the right formulae was hit upon? It could have been hundreds of thousands. In such circumstances, the appearance of life itself is slightly less fantastic.


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## hopewrites (Jun 20, 2016)

More or less fantastic, it brings to my attention the hard work DNA has gone through to get me where I am.
A bit easier to accept my faults (shortsighted, small bones, weak teeth, dyslexia...) when I think of the many times life tried to succeed, the many environmental changes it adapted for, or the myriad of possibilities before it... I just think "Wow. Being me is more awesome than I realised. Good job life ."


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## Stephen Palmer (Jun 21, 2016)




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## Vertigo (Jun 21, 2016)

You will never get two different species interbreeding; that is, I think, the fundamental criterion for determining that they are different species. Parallel evolution is very common, where two completely different and unrelated species have evolved into the same or similar niche. However, though their behaviour and even appearance might end up similar their DNA will not and chances of the DNA becoming sufficiently similar to permit interbreeding are probably statistically vanishingly small.


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## BAYLOR (Jun 21, 2016)

Vertigo said:


> You will never get two different species interbreeding; that is, I think, the fundamental criterion for determining that they are different species. Parallel evolution is very common, where two completely different and unrelated species have evolved into the same or similar niche. However, though their behaviour and even appearance might end up similar their DNA will not and chances of the DNA becoming sufficiently similar to permit interbreeding are probably statistically vanishingly small.



Tell that to Mr Spock.


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## Dave (Jun 21, 2016)

You mean, to his mother and father? Or to Captain Kirk?


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## Hilarious Joke (Jun 21, 2016)

I think I recall reading in 'The Science of the Discworld' that earth's history is so massive that there may well have been another species as intelligent as us somewhere along the way and we just haven't found any traces of it. Or have I got that completely wrong?


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## Dave (Jun 22, 2016)

Hilarious Joke said:


> ...there may well have been another species as intelligent as us somewhere along the way and we just haven't found any traces of it...


They must have been much cleaner than us then - no pollution or waste. Seriously, there would be bones and buildings. However, 'The Science of the Discworld' would not be a book I could easily disagree with given the astrophysics behind the four elephants and giant turtle.


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## 2DaveWixon (Jun 22, 2016)

Dave said:


> They must have been much cleaner than us then - no pollution or waste. Seriously, there would be bones and buildings. However, 'The Science of the Discworld' would not be a book I could easily disagree with given the astrophysics behind the four elephants and giant turtle.



I've seen this theory around, and as I recall, in most iterations the theory includes a very, very long span of time between that ancient life/civilization, and us -- time enough, for instance, for the geological processes of the Earth to tear apart and/or bury most relics.
Do I buy it? No. I can certainly appreciate, and look with interest at, the speculation that life might have come about on more than one occasion, and that fish might have come to land more than one time (certainly those speculations are true to the entire theory of evolution).
But for life to have gotten as far as making a previous civilization? That's harder to swallow. (That said, as a good fan of sf and f, I love it!)

(Who can say whether such a previous life form had bones at all? Maybe they were similar to jellyfish?)(And intelligent jellyfish would generally be unable to manipulate hard matter enough to build temples, etc. So they lived in burrows in the ocean floor, and left no buildings... It could happen!)

(And, just for entertainment value, I will note that a moment ago, looking at the list of recent postings on the home page, I noted that the mention of Dave's last post was curtailed to "Fish may have evolved to live on..." -- and, my mind, being beyond my control, finished that with "...cheeseburgers." Well, that's just how I am...)

(another) Dave


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## Brian G Turner (Jul 26, 2016)

And yet they continue to look for a single ancestor for all life:
Universal ancestor of all life on Earth was only half alive


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## Ray Pullar (Jul 26, 2016)

Single originating event and common descent from it is more likely than many independent ones.


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## Vertigo (Jul 26, 2016)

Ray Pullar said:


> Single originating event and common descent from it is more likely than many independent ones.


I would go further than "more likely"; I mean what are the chances of totally independent origins resulting in common shared genes? It's just too unlikely to be possible. In my opinion if there were any other abiogenesis events then they were less successful and were out-competed by the one we know. However I think that also pretty unlikely as in the early days there was plenty of resources to go around (therefore less need for competition) and I'd have thought any other life would have at least reached fossil levels before being eliminated and there's no real evidence for that.


Brian Turner said:


> And yet they continue to look for a single ancestor for all life:
> Universal ancestor of all life on Earth was only half alive


I think that's really fascinating, Brian. It makes absolute sense that there must have been a half way stage (and quarter way and eighth way....) in the origin of life, whereby there was something that shows many but not all of the features we would identify with life. Although we talk about abiogenesis as thought it was an instant (biblical even) sudden leap from inanimate to animate, it's far more logical for that to have happened gradually and it's fascinating that hydrothermal vents might have provided the initial crutch needed before life managed to evolve all the required processes.


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## Dennis E. Taylor (Jul 26, 2016)

Ray Pullar said:


> Single originating event and common descent from it is more likely than many independent ones.



It also _could_ be that there were multiple originating events at around the same time, but all died out save one. There would be no record. However, if this was the case, I think it would mean that the particular environment was prone to generate a particular type of life, so I'm not sure we'd be able to tell them apart at this point anyway.


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## Vertigo (Jul 26, 2016)

Bizmuth said:


> It also _could_ be that there were multiple originating events at around the same time, but all died out save one. There would be no record. However, if this was the case, I think it would mean that the particular environment was prone to generate a particular type of life, so I'm not sure we'd be able to tell them apart at this point anyway.


I disagree, in as much as, yes, there may have been other independent events that subsequently died out but if they didn't die out the chances of them duplicating identical sets of anything as complex as genes is so unlikely as to be virtually impossible even if they were 'created' by the same evnironment. And they would therefore be easily identifiable as they wouldn't share the common gene sequences all life shares. Remember that DNA and genes in particular are essentially just sets of instructions and the chances of two completely different sets of instructions being complementary and sufficiently compatible to allow cross breeding is hugely unlikely.


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## Brian G Turner (Jul 26, 2016)

I'm suspicious of humanity's predilection for trying to apply a simple answer for complex problems. 

We've seen in the fish example that the potential for life to have moved from the sea to land could have happened multiple time - we've seen in another thread about how the idea of modern humans originating from a single ancestor is now regarded as ridiculously over-simplified.

If there's a single ancestor to all life on earth then it presumes that abiogenesis is effectively a miraculous occurrence - so improbable as to be against natural laws. However, if there is an ordinary physical process that, under certain conditions, makes such a process possible, then IMO there is no way all life began from a single miracle cell, but instead, that the process would have resulted in multiple occurrences, even if within the same immediate location. 

And as has been seen, the swapping of genes is especially common among simple lifeforms - therefore IMO rather than trying to identify a single individual, it would seem more realistic to identify a single _community_. And that's presuming that abiogensis occurred only once on earth. IMO - as with hominids - we are eventually going to find that the answer is far more complex than that.

2c.


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## Dave (Jul 26, 2016)

Brian Turner said:


> IMO there is no way all life began from a single miracle cell, but instead, that the process would have resulted in multiple occurrences, even if within the same immediate location.
> 
> And as has been seen, the swapping of genes is especially common among simple lifeforms - therefore IMO rather than trying to identify a single individual, it would seem more realistic to identify a single _community_.


I would also point out mitochondria as clearly being examples of some kind of small proto-cell that were enclosed and engulfed by some larger proto-cell. I suggest that something very similar must have happened many different times before this actually "worked." Then you have clumps of identical single cells differentiating and having different properties but working together as a colony before ultimately evolving into a single organism. It seems very unlikely to me that that would have worked on the first occasion, but it obviously happened more than once in different ways on several different occasions to produce different kinds of differentiated cells. 

IMO this kind of repetition over great lengths of time makes what Brian describes even more likely.


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## Vertigo (Jul 27, 2016)

Well I'm absolutely no expert in this field (or any except software really!) but I just struggle to image how such swapping of genes could happen between anything that is not already related. It seems to me that even in the simple 'half life,' described in another recent thread, that half life is still chemically extremely complicated and I just fail to imagine a situation where another equally complex chemical 'life form' would even have compatible genes to swap. The assumption being made here, and I consider it to be a huge assumption, is that two separate completely independent creation events would present such an incredible coincidence as to be using a gene mechanism so similar that they could swap those genes. It just seems to me to be so far outside the realms of probability and far more unlikely than the idea of one successful creation (possibly/probably after many 'failed' attempts as Dave suggests) which then goes on to duplicate itself. Once it has achieved that it is almost inevitable that, with nothing except catastrophe to stop it, it will eventually colonise every possible niche on the planet.

I think it comes down to a number of facts for me - though I'm not sure if they are all 'facts':

Life is an incredibly complicated chemical process.
All life on Earth shares a lot of genes suggesting strongly that it is all related.
Only extremely closely related DNA can naturally combine (cross breed). Any significant difference and you have a different species and natural cross-breeding simply will not happen (without us doing the genetic intervention/meddling).
Even when closely related, such as chimpanzees who share 98% of our genes, we still can't cross breed with them

So the idea that a completely different life form would have the same sort of genes that would allow combination seems highly unlikely.

I would also add that the assumption that such a thing could happen naturally extrapolates to the assumption that all life in the universe (assuming there is other life) will be equally similar. If not then why is there no other completely different life to be found here on such a life friendly planet as Earth? In other words if we are saying that there have been many different abiogenesis events on Earth and they have _all_ somehow been sufficiently compatible to merge then the same should be true across the universe, at least on any planet remotely similar to the Earth.


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## hopewrites (Jul 28, 2016)

My understanding is that the more complex organisms have harder times crossbreading than simpler organisms.

If DNA is instrustions, think life as things to be built. Simple organizems would be like bicycles or skate boards. Easy to interchange parts -cross breed. But the more complex you get, motor bikes cars, planes, space stations... the harder it is to find another manufacturer who has compatible parts.
(Yes I know this is an imperfect analogy because manufacturers will purposely make their parts NOT be interchangeable where possible so you have to buy their parts, often from their mechanics...)

New or Pre life wriggling around in what I've always heard called "primordial soup" swapping bike tires and chains, trying out new and better seats handle bars, adding and dropping features like bells baskets or umbrellas, expanding to 2-12 person bikes contracting back down... Seems eminently plausible to me.

Once bio-technology reaches the stage we humans are at, yeah it's going to be hard to find something, even by the same manufacturer, with enough interchangeable parts for interbreeding.


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## Stephen Palmer (Jul 28, 2016)

I must once again point to this exceptional book, which gives answers to the above questions, and more. Buy! you won't regret it…


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## Brian G Turner (Jul 28, 2016)

Vertigo said:


> I'm absolutely no expert in this field



Neither am I - everything I say is personal conjecture. 



Vertigo said:


> I just struggle to image how such swapping of genes could happen between anything that is not already related



It's still relatively new to science - ie, not properly understood - but some living organisms can, under certain conditions, absorb genetic material from their environment into their own DNA:

Horizontal gene transfer - Wikipedia, the free encyclopedia


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## Vertigo (Jul 28, 2016)

Yes but that is genes. Why should an independently created life form even have genes or at least chemically compatible genes. The assumption being made here is that DNA with genes organised exactly as our are is the only way life can happen. And that may well be right (after all we've yet to find any evidence for any other mechanisms despite how many chrons like to speculate on life that can thrive in a high radiation environment which DNA certainly can't) but even if there was an completely independent DNA based life form I still can't image that it's 'genes' would be compatible with ours. It just seems so unlikely.

The way I look at it genes are like biological bits of software and this all seems about as likely as the virus in Independence Day being able to infect a completely alien operating system. Sure they might both use binary code - but that won't make them compatible.

And yes @Stephen Palmer it is on my list and I will get around to it... sometime!


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## Brian G Turner (Jul 28, 2016)

Vertigo said:


> Why should an independently created life form even have genes or at least chemically compatible genes. The assumption being made here is that DNA with genes organised exactly as our are is the only way life can happen.



Oh, totally agree - almost certainly there are other possible variations.

What I'm suggesting is that if you have a specific set of conditions that can give rise to abiogenesis, then isn't it possible that other structures - following the same pattern - could also have developed in the immediate locality? 

And if similar conditions and localities exist in a general area, then is it possible for similar lifeforms - perhaps some with key differences - to also independently develop?

The example given for a single ancestor is that of forming at a hydrothermal vent, but in the modern world different systems of hydrothermal vents have their own unique yet similar species.

And here's something to complicate things - there has long been an argument within science that life arrived from space on meteorites or within comets. We know bacteria can survive in space - heck, even Water Bears can. So...even if life began on earth, what if additional building blocks for life arrived from space that allowed for completely new genes to be assimilated and/or developed - thus giving evolution a big push?


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## J Riff (Jul 28, 2016)

We must ask the ancient Spider-gods. They probably were flying around millenia before any birds, watching it all unfold. That's my theory. *


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## Stephen Palmer (Jul 29, 2016)

Horizontal gene transfer is for bacteria & archaea.


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## Vertigo (Jul 29, 2016)

Brian Turner said:


> Oh, totally agree - almost certainly there are other possible variations.
> 
> What I'm suggesting is that if you have a specific set of conditions that can give rise to abiogenesis, then isn't it possible that other structures - following the same pattern - could also have developed in the immediate locality?
> 
> ...


I think your first point might be possible but only at the most basic and very earliest stages of life; the higher the complexity the less likely that sort of mechanism is, but even at the most basic level, for me, the complexity already present before you get even the most basic sort of half alive suggests a single event far more likely than the merging of multiple events.

Yes there are different species at different vents but today those species share DNA (along with all other life) so I still feel colonisation to be more likely than separate creation.

I'm afraid I've always been sceptical of the whole panspermia theory primarily because it just pushes the problem back further. If life came from comets etc. then where did that life originate? It's highly unlikely to have originated on the comets themselves. Just because they have organic compounds does not make them suitable for abiogenesis, I would think vacuum would still be a highly hostile environment for the creation of life. Ultimately the idea that an environment that is fundamentally friendly to life (liquid water etc.) would fail to produce life itself but instead be colonised from space - an environment far far more hostile to life - just seems immensely improbable and, for me, fails the Occams razor test.



Stephen Palmer said:


> Horizontal gene transfer is for bacteria & archaea.


But even then they already share the same DNA mechanism; they are already related.


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## Brian G Turner (Aug 10, 2016)

Just adding a couple of notes to this thread from Astrobiology magazine:

Evolution Influenced By Temporary Microbes - Astrobiology Magazine



> volutionary biologists often think about evolution as working on the level of organisms, with the individuals that are best adapted to their environments most likely surviving to pass on their adaptations to their descendants and perhaps to their species as a whole. A recent tweak to this concept is the so-called hologenome theory of evolution, which considers evolution working on the level of the holobiont.
> 
> However, some microbes do not fit well inside the hologenome theory of evolution for a number of reasons.



New fossil evidence supports theory that first mass extinction engineered by early animals - Astrobiology Magazine



> Newly discovered fossil evidence from Namibia strengthens the proposition that the world’s first mass extinction was caused by “ecosystem engineers” – newly evolved biological organisms that altered the environment so radically it drove older species to extinction.


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## Dave (Aug 14, 2016)

I do see your points Vertigo and you may well be right. Certainly, no one should take what I have said as "truth" as it was just speculation.



Vertigo said:


> I'm afraid I've always been sceptical of the whole panspermia theory primarily because it just pushes the problem back further. If life came from comets etc. then where did that life originate? It's highly unlikely to have originated on the comets themselves.


You are correct in this, it only means that the life came from elsewhere - a planet that no longer exists, a God or a "godlike" being (the preservers in 'Star Trek') or the @J Riff  spider-gods. Therefore, it explains nothing about the origin of life unless it was a miraculous event.

However, if the Urey-Miller experiment option is true, and it happened within different solutions of organic molecules in different pools of water drying on the shores of ancient Earth oceans, then I see no reason why conditions could not be such that the same event happened repeatedly. In fact, if it was possible chemically once, I think it must have been possibly frequently. 

For me, it comes down to a question of whether it was a miraculous one-off event, or if it is just a natural extension of universal physical and chemical constant values that were set at the time of the big bang. If the latter is true, then it stands to reason that it must be repeatable.


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## Vertigo (Aug 15, 2016)

I do agree with you @Dave, that it might have happened several times in the way you describe. But the chances of each separate event producing something as complex as genes that could actually be compatible with each other seems remote. So if it happened multiple times I suspect it's most likely that only one 'variety' survived in the end. Whether that's survived the environment or survived competition is probably equally likely. But I'm convinced we all come from a single event. In fact Nick Lane argues that there was only one single event that separates simple stuff like bacteria from complex life based on the same arguments. So maybe we're looking at the wrong point. Maybe there were many events that created simple bacteria and archaea but only one single event where complex life formed. I don't suppose we ever will know the full answer.


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## Brian G Turner (Mar 17, 2017)

And apparently some species of fish are still evolving to move on land:
These fish are evolving right now to become land-dwellers


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## BAYLOR (Mar 17, 2017)

Brian G Turner said:


> And apparently some species of fish are still evolving to move on land:
> These fish are evolving right now to become land-dwellers



I for one welcome our new Fishy Overlords.


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