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First 'Rule' Of Evolution Suggests That Life Is Destined To Become More Complex

by ScienceDaily

Thanks to SPS for the link.

http://www.sciencedaily.com/releases/2008/03/080317171027.htm

First 'Rule' Of Evolution Suggests That Life Is Destined To Become More Complex

ScienceDaily (Mar. 18, 2008) — Researchers have found evidence which suggests that evolution drives animals to become increasingly more complex.

Looking back through the last 550 million years of the fossil catalogue to the present day, the team investigated the different evolutionary branches of the crustacean family tree.

They were seeking examples along the tree where animals evolved that were simpler than their ancestors.

Instead they found organisms with increasingly more complex structures and features, suggesting that there is some mechanism driving change in this direction.

"If you start with the simplest possible animal body, then there's only one direction to evolve in — you have to become more complex," said Dr Matthew Wills from the Department of Biology & Biochemistry at the University of Bath who worked with colleagues Sarah Adamowicz from from the University of Waterloo (Canada) and Andy Purvis from Imperial College London.

"Sooner or later, however, you reach a level of complexity where it's possible to go backwards and become simpler again.

"What's astonishing is that hardly any crustaceans have taken this backwards route. Instead, almost all branches have evolved in the same direction, becoming more complex in parallel.

"This is the nearest thing to a pervasive evolutionary rule that's been found.

"Of course, there are exceptions within the crustacean family tree, but most of these are parasites, or animals living in remote habitats such as isolated marine caves.

"For those free-living animals in the 'rat-race' of evolution, it seems that competition may be the driving force behind the trend.

"What's new about our results is that they show us how this increase in complexity has occurred. Strikingly, it looks far more like a disciplined march than a milling crowd."

Dr Adamowicz said: "Previous researchers noticed increasing morphological complexity in the fossil record, but this pattern can occur due to the chance origination of a few new types of animals.

"Our study uses information about the inter-relatedness of different animal groups — the 'Tree of Life' — to demonstrate that complexity has evolved numerous times independently."

Like all arthropods, crustaceans' bodies are built up of repeating segments. In the simplest crustaceans, the segments are quite similar - one after the other. In the most complex, such as shrimps and lobsters, almost every segment is different, bearing antennae, jaws, claws, walking legs, paddles and gills.

The American biologist Leigh Van Valen coined the phrase 'Red Queen' for the evolutionary arms race phenomenon. In Through the Looking-Glass Lewis Carroll's Red Queen advises Alice that: "It takes all the running you can do, to keep in the same place."

"Those crustacean groups going extinct tended to be less complex than the others around at the time," said Dr Wills.

"There's even a link between average complexity within a group and the number of species alive today.

"All organisms have a common ancestor, so that every living species is part of a giant family tree of life."

Dr Adamowicz added: "With a few exceptions, once branches of the tree have separated they continue to evolve independently.

"Looking at many independent branches is similar to viewing multiple repeated runs of the tape of evolution.

"Our results apply to a group of animals with bodies made of repeated units. We must not forget that bacteria — very simple organisms — are among the most successful living things. Therefore, the trend towards complexity is compelling but does not describe the history of all life."

This research was recently published in the Proceedings of the National Academy of Sciences.

Adapted from materials provided by University of Bath.

Posted: Tuesday, March 18, 2008 | Permalink

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1. Comment #145967 by VanYoungman on March 18, 2008 at 12:13 pm

So that explains me.

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2. Comment #145980 by Steve Zara on March 18, 2008 at 12:47 pm

I think this could be misleading, as they are looking for only a superficial kind of complexity. Virtually all the complexity of an organism is within cells, and there is clear evidence for reduced complexity in some evolutionary lines.

Humans only have a few tens of thousands of genes, yet even supposedly "simple" animals like amphibians can have far larger genomes than us. They can operate at a far wider range of internal temperatures, producing different enzymes to deal with different environments. They can take various developmental paths from egg to adult depending on the circumstances.

If you want to see real complexity, take a look at the amoeba, a single-celled organism. It has a genome of 290 billion base pairs - 100 times that of humans!

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3. Comment #145997 by Geoff on March 18, 2008 at 1:10 pm

I think it's fair to address phenotypic complexity separately though, Steve.

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4. Comment #145999 by Vincevl on March 18, 2008 at 1:11 pm

Each individual creature ever is potentially the start of a branch in the Tree of Life. Your Dad is the transitional form between your granddad and you.

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5. Comment #146003 by Steve Zara on March 18, 2008 at 1:15 pm

I think it's fair to address phenotypic complexity separately though, Steve.

If I could change that to, say, structural and behavioural complexity I would be more comfortable.

You should know me by now - I like to try to throw in a slightly skewed viewpoint into a discussion to stir things up.

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6. Comment #146007 by Epinephrine on March 18, 2008 at 1:21 pm

Interesting, but hardly surprising.

To simplify things incredibly, changes result from either changing a gene, adding a gene, or subtracting a gene. Since in general you will only have added genes that were advantageous, removing them will not be as likely as adding others.

There would be some cases in which an earlier addition is not as useful now, and it could then be removed (and not surprisingly, this is seen - loss of hair on cetaceans as an example, loss of colour vision in many mammals, loss of vitamin c production in primates) in a sort of scaffolding removal, but more often than not, if something presented an advantage when it was selected for it will continue to present an advantage.

Since overall it is more likely that changes will result from addition rather than deletion of genes, it is not surprising that the tendency over time is for greater complexity.

Changes in body plan are interesting though - I had read once upon a time that we are going to see continual reductions in the variety of bodyplans, but I'm not sure whether I agree - certainly some groups are more resistant to change than others - tetrapods are all still recognisably tetrapods, and are unlikely to become hexapods, but the arthropods can apparently lose and gain segments much more easily than we can. Is (are) mount(s) improbable truly unidirectional?

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7. Comment #146026 by chuckgoecke on March 18, 2008 at 1:47 pm

I can see it now.... Some intelligent designer will be attributed with pushing this drive to complexity. Rather than seeing this, as it really is, evidence of a natural process that leads, naturally to higher and higher complexity, the enemy will twist this around in exactly the opposite way. Oh well, they always do. Very interesting, if a bit obvious, to anyone who's ever looked at the fossil record.

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8. Comment #146030 by EnlightenedBlasphemy on March 18, 2008 at 1:49 pm

This is truly amazing and fascinating, I give it 5 minutes more before the Intelligent design people claim it as their own.

"you see you see!" they clap their hands and jump up and down excitedly. "this is God at work! See how it all gets more complex all the time. It's obvious that jesus died for our sins..."

Meanwhile at the other corner of the big playground we inhabit, the young earth creationists are kicking sand despondently and pretending they didn't hear a word of it.

*my apologies if i have broken some forum taboo by mentioning religion under a purely scientific article.

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9. Comment #146032 by Steve Zara on March 18, 2008 at 1:51 pm

Changes in body plan are interesting though - I had read once upon a time that we are going to see continual reductions in the variety of bodyplans, but I'm not sure whether I agree - certainly some groups are more resistant to change than others - tetrapods are all still recognisably tetrapods, and are unlikely to become hexapods, but the arthropods can apparently lose and gain segments much more easily than we can. Is (are) mount(s) improbable truly unidirectional?

This is indeed a very interesting question. I suspect that the mounts improbable are unidirectional, if only because the results of climing those mountains tend to occupy available niches. If there was some mass extinction that took us back to invertebrates, who knows what the results might be?

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10. Comment #146034 by EnlightenedBlasphemy on March 18, 2008 at 1:52 pm

Dammit Chuck, If i hadn't been spell checking my post i could have beaten you to the punch on the ID whackjobs

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11. Comment #146043 by Tyler Durden on March 18, 2008 at 2:07 pm

And the first rule of Fight Club is - You do not talk about Fight Club!

I'll get me coat :)

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12. Comment #146064 by Enlightenme.. on March 18, 2008 at 2:54 pm

If there was some mass extinction that took us back to invertebrates, who knows what the results might be?

An increased evolvability speed giving rise to a high incidence of cancer for some time I reckon.

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13. Comment #146071 by Vadjong on March 18, 2008 at 3:11 pm

Higher complexity is just an euphemism! I call it tinkering upon tinkering. You'll never down-tinker anything unless you scrap it and start anew.

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14. Comment #146087 by SmartLX on March 18, 2008 at 3:41 pm

Seems to me you only need one exception to bring this First Rule crashing down, and PZ Myers might have found it: the dicyemid mesozoa.

http://scienceblogs.com/pharyngula/2008/03/dicyemid_mesozoa.php

Have I got it wrong, or is PZ of the opinion that this little critter evolved from something more complex?

Maybe the First Rule only applies to crustaceans.

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15. Comment #146097 by Epinephrine on March 18, 2008 at 3:50 pm

SmartLX:

The article actually acknowledges the existence of exceptions. They say, "hardly any crustaceans have taken this backwards route" and, "Of course, there are exceptions within the crustacean family tree, but most of these are parasites, or animals living in remote habitats such as isolated marine caves."

It's not really much of a rule, more of a general principle that has known exceptions.

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16. Comment #146101 by SmartLX on March 18, 2008 at 3:53 pm

Ah, and the dicyemid mesozoa is a parasite. Whoops, went off half-cocked.

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17. Comment #146108 by Driver on March 18, 2008 at 4:04 pm

by Enlightened Blasphemy:

"'you see you see!' they clap their hands and jump up and down excitedly. 'this is God at work! See how it all gets more complex all the time. It's obvious that jesus died for our sins...'"

This won't contribute to the discussion on this article, but I just had to say that when I read that I laughed out loud. Then I had to come up with a story for my coworkers about the subject of my laughter. I couldn't admit to them that it was their faces I saw in my head as I read that comment.

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18. Comment #146143 by blu on March 18, 2008 at 5:08 pm

This is hardly surprising when considered in light of maintaining a equilibrium. The more complex something becomes, the more difficult it is to maintain and the more energy needed to for it to live. On the other hand, greater complexity allows for a greater number of survival strategies. So, as things evolve, they will tend to become more complex, eventually reaching a plateau where further complexity is counter productive. But less complexity will likewise need to provide a survival boost for it to be selected for. If the boast is provided simply for the greater simplicity and less energy use, then that suggests that the mutation that led to the greater complexity would not have been selected in the first place. Thus we can see that a wholesale string of changes that lead to more simplicity is unlikely. This is the logical results of the processes pointed out in "Climbing Mount Improbable", all change must be an improvement.

Of course, parasites can move in this direction because they are able to improve by discarding those biological processes that are now redundant when they embarked on parasitism in the first place.

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19. Comment #146153 by the_ultimate_samurai on March 18, 2008 at 5:28 pm

changes result from either changing a gene, adding a gene, or subtracting a gene. Since in general you will only have added genes that were advantageous, removing them will not be as likely as adding others.

im not sure that is true.
for instance the removal...not exactly of a gene...but of a base pair will result in a change to that gene, you can get profound amount of change in a genome by multiple deletions of basepairs.
also since metabolism and genome size are proportional (creatures with larger genome have slower metabolism as it takes longer to copy the genome for mitosis.) if nature selects for higher metabolism extraneous bases, junk dna, etc would be likely to be deleted.
complexity is only prefered in so much as its affordable, nature has this kind of economy about it on energy, so if it takes x energy to do something, nature selects for something that takes x/y energy instead. there is a natural tradeoff.
efficiency i imagine is probably selected more than complexity. so the number of base pairs for instance is less important than the effectiveness of those base pairs, esspecialy if metabolism is important (as it is in creatures that need to run for, or from, their food. this too is a tradeoff, slower metabolism means you need to eat less, but you tend to be slower and if you need to catch something fast...)

equally such there is no exact corelation between size of brain and the ability of that brain, what matters is the efficiency of that brain. so if you need a realy good brain, nature will select for a more efficient or larger brain. (if efficiency is constant brain size and capacity will be dirrectly proportional, if size is contant then efficiency and capacity will be dirrectly proportional. if there is a selective pressure for both a small head and a powerful brain efficiency would be the only option. of course cranial capacity and thickness of skull tend to be proportional too. so lots of trade offs involved.)

there is no real way to rate the complexity of a genome so i think looking at it on a genotypical way would be inappropriate. more base pairs does not more complex make.

but yeah, this is an interesting article, i always thought simplification was possible, but perhaps that was forcing design onto biology..of course if something becoming more efficient counts as more simple i think there are example of that.

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20. Comment #146189 by Opisthokont on March 18, 2008 at 6:09 pm

Evolution is far more than a change in genes. Regulation of genes is at least as important as the genes themselves, and changes in regulation are not as easy to trace as changes in genes. Genes are regulated both by elements on the chromosome and by environmental factors, and environmental factors include what other cells are nearby. Development of complexity is itself far more complex than simply the evolution of genes.

Likewise, multicellular organisms are far more than the sum of their cells. Much of the matter in our tissues is not cellular: bone, skin, and blood, for instance, are largely comprised of extracellular material. This material is synthesised and maintained by cells, of course, and much of that is done by genetic programs -- but much of it is not, dependent instead upon intercellular signalling. Some of it is dependent upon signalling from outside the animal, such as by the mother during gestation. These interactions, more than anything else, are responsible for the complexity of modern life. Above a certain minimal complement of genes, the size of the genome is irrelevant to complexity.

As for directionality, this article implies that the evolution of more complex developmental networks (necessary for more-complex forms of multicellular life) is inevitable. Perhaps that is so (and I think it likely). However, confirming that hypothesis will involve far more than merely analysing genomes for "complexity", however one defines it.

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21. Comment #146192 by Enlightenme.. on March 18, 2008 at 6:17 pm

So.. how do blind cave fish evolve?
Is it sudden deletions of the whole set of blueprint for eyes - 'devolution'?

Or is it additional information for not wasting energy building eyes, followed by eventual withering away of the superceded dna?

Either path could add up to the same number couldn't it?

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22. Comment #146195 by chuckgoecke on March 18, 2008 at 6:27 pm

In my previous comment I eluded to increasing complexity being easy to see in the fossil record. One group that this is clearly demonstrated in, I recall(from my geology days at U or Mn, Morris, PZ Meyers' current university), were the Mesozoic Ammonites. In particular, one can see increasing complexity in the suture pattern on the sides of the shells. Ammonites are shelled cephalopods like the contemporary nautilus, but which died out with the dinosaurs at the end of the Cretaceous. The sutures are expressions of the walls formed between the current and previous body compartments, added as the animal grows. The suture patterns, which started out simple, became steadily more complex, and dendritic in later forms, through the Cretaceous. Additionally, the shells became more ornate with ridges and ornamentation. These fossils are abundant in the Pierre Shale which covers much of western South Dakota, and were the subject of my Senior Paleontology Project in 1979. (Several of my most beautiful specimens are in a display cabinet at my Republo-Christian brother's house, which were plundered from my collections while I was a grad school - if that ain't ironic).

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23. Comment #146212 by notsobad on March 18, 2008 at 7:19 pm

It's true!

Crustaceans will evolve into Doctor Zoidberg.

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24. Comment #146218 by Wosret on March 18, 2008 at 7:33 pm

It's become obvious to me now, in order to fend off extinction, we need to eliminate any species that is equal or greater complexity to ourselves.

We need to get them before they get us!

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25. Comment #146253 by dragonfirematrix on March 18, 2008 at 8:26 pm

To quote the title of this article…

"First 'Rule' Of Evolution Suggests That Life Is Destined To Become More Complex"

Well…

I think this is going to be the hardest thing with which the religious have to deal, especially since they have not evolved for quite some time.

Again, quoting the article…

"Sooner or later, however, you reach a level of complexity where it's possible to go backwards and become simpler again."

I think the religious are already regressing, and they are trying to require the rest of us to do the same.

As for me, I am sixty, which means I am on my way to being extinct anyway, but I will not first regress.

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26. Comment #146271 by Epinephrine on March 18, 2008 at 9:28 pm

@the_ultimate_samurai

You quoted me, selectively removing the rather important, "To simplify things incredibly," with which I prefaced it.

I of course agree that the situation is more complex than my gross oversimplification, but the point was that it's long been thought that evolution, acting as a ratchet of sorts, is unlikely to function well in reverse. It's not surprising that the ratchet gradually advances.

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27. Comment #146327 by Koreman on March 19, 2008 at 12:50 am

@ 8. Comment #146030 by EnlightenedBlasphemy
" *my apologies if i have broken some forum taboo by mentioning religion under a purely scientific article. "

No problem. Mentioning religion in online discussions regarding scientific topics is called Godlose's Law.

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28. Comment #146328 by Richard Morgan on March 19, 2008 at 12:51 am

MUSIC NEWS

Due to the number of requests that I have had for the music I created to accompany an excerpt from The Lava Lizard's Tale, I have uploaded an MP3 of "Fingerprints �" past time" into a second stand-alone player on the Fleabytes Myspace.
This composition my be downloaded by:
1) Rationalists
and / or
Welsh persons, and / or
Musically gifted Lava Lizards.

http://www.myspace.com/fleabytes

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29. Comment #146336 by Steve Zara on March 19, 2008 at 1:12 am

Comment #146189 by Opisthokont

Above a certain minimal complement of genes, the size of the genome is irrelevant to complexity.

I am so going to disagree with this. Cells don't have all that DNA in just for fun. It takes energy to maintain and copy. It looks like even supposedly non-coding DNA serves a purpose, which the production of regulatory RNA.

Genes are regulated both by elements on the chromosome and by environmental factors, and environmental factors include what other cells are nearby.

For genes to be regulated by environmental factors, they have to code for the ability to be regulated by them. It's all to do with DNA.

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30. Comment #146442 by Geoff on March 19, 2008 at 5:00 am

15. Comment #146088 by Brian English

Sea squirts hatch with a brain. When they find a rock to attach to, they digest their brain as it's no use to them any more. Is that more or less religious?

typo corrected...

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31. Comment #146464 by the_ultimate_samurai on March 19, 2008 at 5:45 am

oh i saw the part about it being a simplification and took it into account, i only quoted the other part because it was all i was concerned with.

perhaps it was more for my sake to get a "yes" or "no" or if im vastly mistaken, and explanation of why than realy any attempt at refutation.

i may have phrased it wrong, as i often do...i wasnt meaning to misquote you, i was more seeking elaboration.

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32. Comment #146486 by Shaden on March 19, 2008 at 6:12 am

by Mitchell Gilks

It's become obvious to me now, in order to fend off extinction, we need to eliminate any species that is equal or greater complexity to ourselves.

Isn't that the plot of X-Men?

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33. Comment #146504 by j.mills on March 19, 2008 at 6:37 am

Willis reckons life's long tribulations
Make complexity grow in crustaceans.
Shellfish genes do their stuff
And work out what's enough
Without recourse to his complex equations!

I'll get my coat.

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34. Comment #146525 by Luthien on March 19, 2008 at 7:00 am

My definition of Evolution by natural selection:

Hey, whatever works for you!

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35. Comment #147260 by Luis_Cayetano on March 20, 2008 at 4:51 am

I hardly think this qualifies as a "rule" of evolution. Building complex organisms is energetically expensive, so the question is really why selection would have favoured increased complexity in crustaceans. In other groups that have been studied, there was no overall increase towards complexity. I recommend Stephen Jay Gould's "Full House" for a view on this. Just because the crustaceans have undergone across-the-board complexification doesn't mean you can extrapolate to evolution in general and proclaim that you have uncovered a "first rule". I'm not saying that the researchers are wrong, just that until we've done a wider cataloguing and comparison of complexity throughout the biosphere, making these sorts of claims is going to give the impression of undue eagerness. Some parts of this article made me think, "so what? That's meant to be surprising?" Good on them for making this fascinating discovery, but I fear that they're attempting to draw conclusions that aren't warranted. That the Crustacea have become more complex overall is interesting enough. I'm sure some lessons can be drawn from this, but it seems somewhat wank-headed to think you can make sweeping generalisations from it.

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