1st Rule Of Evolution: Life Destined to Become More Complex

[RichardPrins]

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

Scientists have revealed what may well be the first pervasive ‘rule’ of evolution.

In a study published in the Proceedings of the National Academy of Sciences 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.”

http://www.pnas.org/cgi/content/abstract/0709378105v1

[Dlx2]

Absolutely not.

http://paleobiol.geoscienceworld.org/cg ... t/33/2/182

[lbq]

This is a really ancient chestnut (though in our days of course 'complexity' has replaced the forthright Victorian term 'perfection').

Life did of course start out simple, on a bacterial level. It could not get any simpler, so if it changed, odds were that it had to get more complicated. This is a 'limited drunkard's walk': The drunkard's movements are limited in one direction by the wall of the pub he was just thrown out of, so he can only drift further out in the street. Beyond that, only the pious religious mind (decorated by a Ph.D. no doubt) can discern any general tendency toward greater perfection - oops, 'complexity' - and least of all any inherent i.e. genetical or epigenetical such tendency. Parasites are among the most successful of all organisms, and they do usually exhibit drastical anatomical simplification. Most non-parasitical species too belong to lineages which have not got any more complex for millions of years.

It is really strange what attraction the discredited notions of orthogenesis holds for people who by their education should know better.

[MedGen]

hmmm, I must say that alarm bells were ringing whilst reading that. I think lbq hit the nail on the head again, it's as if they are saying that evolution has a direction too.

[clouded_perception]

What the hell?

I was under the impression that single-celled organisms made up most of the biomass -- indeed that prokaryotes made up most of the biomass -- and that when bred in a lab without significant selective pressures imposed (given enough resources etc. viruses and suchlike tended to become as simple as they possibly could. How does anything translate into a tendency to become more complex? Obviously we're more complex than the ancestors of all life -- there's no way to be less complex -- but why do they think things have an inbuilt tendency for complexity?

[DavidMcC]

hmmm, I must say that alarm bells were ringing whilst reading that. I think lbq hit the nail on the head again, it's as if they are saying that evolution has a direction too.

Clearly, if you talk about the entire tree of life, it isn't moving! However, during a speciation, a particular population moves in a particular direction for a while (determined by some particular, fortuitous mutation), until a new species stabilises.

[MedGen]

hmmm, I must say that alarm bells were ringing whilst reading that. I think lbq hit the nail on the head again, it's as if they are saying that evolution has a direction too.

Clearly, if you talk about the entire tree of life, it isn't moving! However, during a speciation, a particular population moves in a particular direction for a while (determined by some particular, fortuitous mutation), until a new species stabilises.

I was thinking of a more holistic perspective of evolution, rather than specific events. Even then the direction is determined by selection pressures, fitness and such.

[DavidMcC]

Even then the direction is determined by selection pressures, fitness and such.

Absolutely.

[lbq]

Clearly, if you talk about the entire tree of life, it isn't moving! However, during a speciation, a particular population moves in a particular direction for a while (determined by some particular, fortuitous mutation), until a new species stabilises.

Of course. But 'moving' does not automatically mean 'moving in the direction of increased complexity'. A speciating population can just as well move in the direction of decreasing complexity. In the vast majority of cases however the movement is a change on the same level of complexity as before.

The problem with Drs. Wills and Purvis seems to be that they postulate an inherent drive in the direction of greater complexity. Such a drive demands a mechanism, or at least an agent (and Old Man Yahwe will not be considered). Show me the mechanism or the agent, and I will seriously consider their proposal. But there seems to be no such thing.

This is 'good old' orthogenesis again: It was such a wonderful and appealing idea that evolution did inexorably march in the direction of greater perfection, culminating in glorious us, of course. The problem was that no inherent mechanism and no external agent could ever be found, except pious expectation. That was not enough, and orthogenesis died a death in merciful obscurity. Now and then the corpse moves, however; ideas that tickle our vanity are more difficult to exterminate than cockroaches.

[Dlx2]

The Wills et al. paper doesn't postulate a universal trend; they just note that a bunch of lineages within thee crustacea specialize their various limbs over and over in different lineages. This specialization of serial homologues is well-observed in many clades. The question is whether this is a clade-specific trend or a universal trend. Plenty of instances have been described where decreasing complexity can be observed, as in the Marcot and McShea paper I posted above. There is no trend towards "more complex" at all.

[cadman]

The problem with Drs. Wills and Purvis seems to be that they postulate an inherent drive in the direction of greater complexity. Such a drive demands a mechanism, or at least an agent (and Old Man Yahwe will not be considered). Show me the mechanism or the agent, and I will seriously consider their proposal. But there seems to be no such thing.

Whilst I agree that there is no inherent drive within an organism or within the process of evolution towards greater complexity. Wouldnt it not be reasonable to say that increased specialization and the grouping of specialist functions can offer inherrent "natural" advantages to organisms? This inherrent advantage to specialist roles, cooperation etc is a factor that natural selection can act upon? Trees do seem to outcompete moss in the gathering sunshine in forests.

The words evolution and destined when used together should raise alarm bells agreed. But what about "The cooperation of cells with specialist biochemical tasks offers competive advatange over homogenous cells"?

[lbq]

The Wills et al. paper doesn't postulate a universal trend; they just note that a bunch of lineages within thee crustacea specialize their various limbs over and over in different lineages. This specialization of serial homologues is well-observed in many clades. The question is whether this is a clade-specific trend or a universal trend. Plenty of instances have been described where decreasing complexity can be observed, as in the Marcot and McShea paper I posted above. There is no trend towards "more complex" at all.

I do not doubt that the learned doctors are blissfully unaware both of the necessary presupposions and consequences of their idea, and of its murky historical antecedents. They are nevertheless inescapable - and you will not escape them just by throwing in the word 'clade' either.

[Dlx2]

The Wills et al. paper doesn't postulate a universal trend; they just note that a bunch of lineages within thee crustacea specialize their various limbs over and over in different lineages. This specialization of serial homologues is well-observed in many clades. The question is whether this is a clade-specific trend or a universal trend. Plenty of instances have been described where decreasing complexity can be observed, as in the Marcot and McShea paper I posted above. There is no trend towards "more complex" at all.

I do not doubt that the learned doctors are blissfully unaware both of the necessary presupposions and consequences of their idea, and of its murky historical antecedents. They are nevertheless inescapable - and you will not escape them just by throwing in the word 'clade' either.

No, you, are putting words in their mouth via a selective reading of a popular article. I suggest that you read the paper in PNAS. I've been watching creationists debate evolution for years now, and they seem to take the exact same approach: read a popular news account of a scientific paper, jump on a bit of poor word choice or sensationalism, and ignore any attempt to redirect discussion to the subject of the actual paper. Sir, if you want me to take you seriously as an "expert" in evolutionary biology, the least you can do is actually interact with the scientific literature before calling a scientist or group of scientists small-minded. As it stands, you are behaving no differently from Answers in Genesis. Congratulations, you're making the rest of us look bad.

For your reference, the abstract and a link to their supporting material and full paper can be found here:

http://www.pnas.org/cgi/content/abstract/0709378105v1

Adamowicz et al. 2008 does not state that increased complexity is a universal trend. They state that specialization of serially homologous structures (here, arthropod limb) seems to be occurring in an unbalanced manner towards increased specialization of those limbs and limb segments, which does suggest increase in complexity both of limb use as well as gene signaling cascades as downstream genes are recruited in the patterning of limb identity.

Adamowicz et al. 2008 stress in their paper that they are observing a pattern within a clade, that clade being Crustacea. Hence, stating that this is a clade-specific trend is not unreasonable. Just because you're not comfortable with cladistic terminology does not mean that it is "avoiding the point." There are a lot of things in biology nowadays that cannot be discussed easily without appealing to terminology you are unfamiliar with. This is not my fault, and if it bothers you, then you ought to start the arduous process of learning the basics of modern biological techniques.

[Ruben]

Complex for who?
For us to understand? or complex for evolution?
Don't think the term complex will add up for evolution, cause it doesn't know any complex situation.

I think if you look a little with mathematic eyes is sure has to become more complex.
If one specie becomes more complex others will adjust to that, let's say 2 other species.
These two will cause 4 others to become more complex. ect. in order to survive. (just figurative numbers)
Could be that i look at it to easily but it is logical thought.

Cause the some become more complex others will HAVE to follow to a next level of complexity or they extinct.

You can also see that when the situation doesn't require the level of complexity some will lose some of the complexity. Taking example out of cave fish

[JimC]

Dlx2 wrote:

Adamowicz et al. 2008 stress in their paper that they are observing a pattern within a clade, that clade being Crustacea. Hence, stating that this is a clade-specific trend is not unreasonable. Just because you're not comfortable with cladistic terminology does not mean that it is "avoiding the point." There are a lot of things in biology nowadays that cannot be discussed easily without appealing to terminology you are unfamiliar with. This is not my fault, and if it bothers you, then you ought to start the arduous process of learning the basics of modern biological techniques.

Yet another example of your gratuitous, unpleasant, arrogant and patronising attitude towards fellow posters.

Shrink your ego and grow up.

[lbq]

Clearly, somebody made this claim:

1st Rule Of Evolution: Life Destined to Become More Complex. But now the claim has shrunk like the Cheshire Cat, until all that is left is "some lineages sometimes do get more complex". And who disputes that?

All extremely general claims are either false, or trivial. But "the truth is concrete" according to Hegel (and after him Gramsci, and after him Brecht). Specifying the conditions under which a claim is actually non-trivially true - that is, when it actually says something we didn't know before - does often cut claims down to size wondrously.

[Tachion]

Life is always the simplest it can be given the environment it is in. It the the growing complexity of the environment that having more varied lifeforms that creates the seemly complexity increase.

As the niches for living become smaller then life must change to use it.

If you were to destroy 90% of life then the remaining 10% would evolve to a SIMPLER state not a more complex one.

Life is in its simplest form to survive in its environment. Overall this will create a more complex system as the number of different lifeforms increase and life will seem to become more complex, but relative to its environment it has not become more complex.

That is why bacteria has not changed. From its perspective the additional lifeforms have minimal impact on the complexity of its environment.

[susu.exp]

Clearly, somebody made this claim:

1st Rule Of Evolution: Life Destined to Become More Complex. But now the claim has shrunk like the Cheshire Cat, until all that is left is "some lineages sometimes do get more complex". And who disputes that?

Well, somebody has made that claim, but it wasn´t the authors of the paper in question, nor was it Dlx2. Nor would I make that statement, because it is clearly wrong. I don´t think that merits further discussion because that´s not the 1st rule of evolution, nor any rule of evolution at all. However, when you look at the paper it does make an interesting claim and while I can´t acess PNAS from here, this one will be read ASAP. The authors do know that life is not destined to become more complex and I´m willing to bet money on them citing McShea. After all, they use McSheas technique to analyze trends, which you should know, because your first post is indicative of you having read a certain book on baseball which also explains McSheas approach. To stay in the terms introduced by McShea and used by Gould, what Adamowicz et al. 2008 claim is that they´ve found a driven trend in the crustacea. Right now I don´t know how valid that claim is, my main possible objection being that you´ll get a significant "driven" signal by pure chance in some clades if you test enough clades and Adamowicz et al. might have lucked out. But if there actually is a driven trend here, then these results are certainly more than a mere "some lineages sometimes do get more complex".
Now natural selection does not produce driven trends, only passive ones. So if there is a driven trend in the crustacea, we have to find the mechanism that explains it. And no, orthogenesis is not in the running (before you throw that one at me, since you´re seeing proponents of orthogenesis under every carpet, a bit like McCarthy saw Communists everywhere). And if there is a significant increase in extinction rates for taxa with higher limb redundancy, which the abstract seems to hint at, that driver might be species selection. That´s two very interesting statements
a) driven trend to higher degrees of limb specialization
and
b) increased extinction of taxa with high limb redundancy as the driver.

But the person in charge of the press release aparently didn´t think they were spectacular enough and decided to add a BS headline. You´re the science writer of the two of us, so you probably know why that headline will get people to read the popsci articles. I´m infinitely more intrigued by the actual paper...

If you were to destroy 90% of life then the remaining 10% would evolve to a SIMPLER state not a more complex one.

5 mass extinctions during the phanerozoic tell a different tale. For example the ecological complexty of marine ecosystems did not change significantly from the Cambrian to the Permian, nor from the Triassic to the present. However it did dramatically increase directly after the Permo-Triassic extinction (which did kill off >90% of marine species), see Wagner et al. 2006 http://www.sciencemag.org/cgi/content/abstract/314/5803/1289.
At mass extinctions and during the recovery phase, we tend to find species sorting, leading to the preferential extinction of morphologically complex, more individuated specialist taxa, with less complex, less individuated generalists surviving. Then we see a usually passive trend towards higher complexity.

[lbq]

Susu, I agree with you completely. But I suspect that a lot of scientists are so utterly ignorant of the history of the life sciences that they commit the old errors again and again without knowing how old they are, and how utterly refuted they are. 'Those who are ignorant of history are doomed to repeat it.'

[Psi Wavefunction]

Of course our eye prefers to look at things more similar to us (which we arrogantly call 'complex'), and ignores all else. The vast majority of life on earth is bacteria, and those little suckers are not begging to be called 'simple' either - their regulatory mechanisms are, in a way, more efficient and require less processes than ours, but that does not mean they're 'simple'. I think the concept of 'organism' and 'species' tends to fall apart at the prokaryote level - group dynamics seem to be much more drastic there. Since gene transfer on that level no longer requires waiting a generation for a genome to be altered, adaptation occurs much faster. Due to plasmids and transformation and such, bacteria are best viewed on a group level rather than the individual one. This makes them almost multicellular from that perspective! (much like the cellular slime moulds in the 'slug' phase)

And as soon as we start talking group dynamics, complexity becomes unavoidable.

Also, take the slime mould for example - those little amoebae congregate into a 'slug' when conditions are poor, on order to form a stalk with "spores" (amoebae who end up at the top modify their bodies to become 'spore-like', not real spores) and propagate. Mathematical biologists have been all over this - how can these 'stupid' 'simple' little things figure out a way to assemble and form this essentially multicellular 'superorganism' (which moves in a coordinated fashion!), and later change the collective shape to form this fruiting body? Again, a phenomenon of single organisms acting together as something drastically more complex.

There could be so many other examples of this, perhaps numerous undiscovered ones in prokaryota. We know so little of them, that I believe it is WRONG to judge little things as 'simple'. Its simply arrogance on our part.

Oh, and theres this little single-celled organism with a camera eye composed of SUBCELLULAR components. I forget the name (I saw it in a seminar) but it took me a while to get over my awe...

Now, I guess this doesn't disprove that "principle" that things evolve 'towards complexity". However, there's a substantial fallacy there again:

What about the organisms that "didn't evolve"? If organism A splits off into a 'new' organism B and an 'A-like' organism C, it is common to assume that C is A, and B has 'evolved' from it. However, so has C. But we tend to ignore it (staying the same is not as sexy as changing drastically, in our minds) and thus there is an illusion that A->C evolved towards complexity. It may have something to do with probability - there are more ways to be more 'complex' than simple, since there is a hard limit in the simplicity direction. So in an event of a speciation, it is more likely for something to appear more 'complex'.


I propose this first principle of evolution: Things evolve.

And lets scrap the 'complexity' connotation of the word 'evolve'. Evolved is assumed to mean better, more sophisticated, very awesome. Evolved just means 'changed and survived until now'.

The other great apes are just as evolved as we are. Enjoy their company. =D

(try telling your cousins you're more evolved - that may not go over well!)

[Dlx2]

Dlx2 wrote:

Adamowicz et al. 2008 stress in their paper that they are observing a pattern within a clade, that clade being Crustacea. Hence, stating that this is a clade-specific trend is not unreasonable. Just because you're not comfortable with cladistic terminology does not mean that it is "avoiding the point." There are a lot of things in biology nowadays that cannot be discussed easily without appealing to terminology you are unfamiliar with. This is not my fault, and if it bothers you, then you ought to start the arduous process of learning the basics of modern biological techniques.

Yet another example of your gratuitous, unpleasant, arrogant and patronising attitude towards fellow posters.

Shrink your ego and grow up.

Here's a suggestion. Before pontificating on whether or not a paper has any merit, and whether or not scientists are completely ignorant, read the damned paper.

Pontificating on scientific research when you don't know what the research actually is does nobody any good, unless you're simply trying to stroke your ego.

I'm not here with an interest in stroking my ego. I'm here with an interest in discussing the matter at hand. If discussing the science of evolutionary biology breakthroughs is not a matter of interest to this forum, I can certainly find other places to frequent.

[Dlx2]

Susu, I agree with you completely. But I suspect that a lot of scientists are so utterly ignorant of the history of the life sciences that they commit the old errors again and again without knowing how old they are, and how utterly refuted they are. 'Those who are ignorant of history are doomed to repeat it.'

There you go again making vast claims about scientists without actually reading the goddamned paper.

Here's a suggestion, lbq. Start reading the scientific literature rather than making assumptions that do not have anything to do with reality.

[JimC]

Dlx2 wrote:

Adamowicz et al. 2008 stress in their paper that they are observing a pattern within a clade, that clade being Crustacea. Hence, stating that this is a clade-specific trend is not unreasonable. Just because you're not comfortable with cladistic terminology does not mean that it is "avoiding the point." There are a lot of things in biology nowadays that cannot be discussed easily without appealing to terminology you are unfamiliar with. This is not my fault, and if it bothers you, then you ought to start the arduous process of learning the basics of modern biological techniques.

Yet another example of your gratuitous, unpleasant, arrogant and patronising attitude towards fellow posters.

Shrink your ego and grow up.

Here's a suggestion. Before pontificating on whether or not a paper has any merit, and whether or not scientists are completely ignorant, read the damned paper.

Pontificating on scientific research when you don't know what the research actually is does nobody any good, unless you're simply trying to stroke your ego.

I'm not here with an interest in stroking my ego. I'm here with an interest in discussing the matter at hand. If discussing the science of evolutionary biology breakthroughs is not a matter of interest to this forum, I can certainly find other places to frequent.

You have not addressed the central point - your arrogant lack of courtesy to fellow posters.

[Dlx2]

Au contraire. You have not addressed the central point: the fact that you and lbq arrogantly assume to know everything about a scientist's research, methods, results, and competence on the sole basis of a news brief.\

I actually know some of these people in real life. Your arrogant arm-waving is a great deal more rude than anything I've stated here.

[JimC]

Au contraire. You have not addressed the central point: the fact that you and lbq arrogantly assume to know everything about a scientist's research, methods, results, and competence on the sole basis of a news brief.\

I actually know some of these people in real life. Your arrogant arm-waving is a great deal more rude than anything I've stated here.

Confirmation of my opinion.