Evolution and complexity

Just thought I'd pipe in with my 2 cents worth:I guess the best place for me to start would be by explaining how I have come to understand the word "complexity". First, I think it's important to keep it in a biological context. With that in mind, I think of complex organisms as those with the most "parts". But then we have to decide on what constitutes a "part"? Well, in terms of animals, I have viewed parts as organs and organ systems. I'm not a botanist or a mycologist, but I would guess that there are tissues in these groups that could be used to distinguish between complex and simple. I'm sure there are other, more precise definitions out there, but when we are talking about living things, IMHO the definition of complexity should focus on measurable characteristics, otherwise it becomes meaningless.A few people have correctly pointed out that simple life forms far outnumber complex life forms, but that was not really the question. We need to understand that natural selection does not "choose" more complex organsims, it merely selects those that are best adapted to their current environment. So why should we think that evolution leads to more and more complex organisms? The answer is: "we should not". I just think that it's a natural bias on our part (humans) to want to view complex organisms as inevitable, because without such a drive, we would not have evolved. But does such a drive exist?Now, in answer to the question at hand, I think crashfrog stated it quite nicely very early on. There really is no observable evolutionary trend towards increased complexity. I think we all agree that in terms of complex versus simple, things can only get so simple and still be considered "living". If we accept this (and how can we not?), then early on in evolutionary history, life would have had no "choice" but to become more complex. The real test comes later (now?), when we can look at middle lines of descent (the first mammal, the first arthropod, the first tree, etc.) and then look at the evolutionary trends. When we do this, we see that it goes both ways. Some things become more complex, while others become less complex. Importantly, there is no significant difference between the two "directions". Gould's "Full House" does a wonderful job of explaining this, as crashforg (and I must pat myself on the back here too, for I have mentioned this on a few occasions as well) mentioned. I recommend it to anyone that thinks evolution leads to more complex organisms.Anyway, just my contribution to the discussion.

NosyNed:It seems that we have taken what I thought to be a relatively simple concept and transformed it into a complex monster (pun intended). Let me attempt to simplify it once again. If what we’re trying to do is determine if evolution has a drive towards complexity, then we do need to restrict our definition to something both measurable and applicable to living organisms. I think that some of the attempts to define complexity on this thread have gone a bit beyond that. A while back I mentioned organs and organs systems as a measure of complexity. Let me put it another way. Can complexity be meaningful if we define it as the number of differentiated cells within an organism? I’m not talking about the total quantity of cells, but rather the number of different types of specialized cells within the organism. This would of course lead us back to tissues and organs, and organ systems (at least for animals).
One-celled organisms would be the most simple, while mammals would certainly be one of the more complex. But then what happens when we have two organisms that have equal numbers of specialized cells (comparing a chimp to a human for example)? If asked: Are we really more complex than a chimp? my answer would be: It doesn’t matter. But if people do want to answer this question, then between closely related organisms, we can look in more detail at these systems.I think it’s important to remember what we’re trying to do here, which is to determine if evolution is biased towards more complex organisms. Is a lion more complex than a bear? Who cares. Is a lion more complex than a starfish? Yes, if we look at the specialization of cells within each species. Is a rotifer more complex than a gastrotrich? Again, who cares. But a rotifer would be more complex than a sponge. However, the more important question is if evolution drives towards these more complex organisms or are they merely an artifact of the left hand wall? My understanding of the evidence is that they are merely an artifact and not the result of an inherent drive.So I guess what I’m asking is if it is reasonable to use the specialization of cells within an organism as a measure of relative complexity?

NosyNed:Thanks for the quick response. I do think you jumped the gun a bit on this first example however. My idea would answer this one quite simply. Looking at the differentiation of cells we see the development of cardiac muscle in the dog and the connective tissue of bone as well. So by my measurements, even a cursory glance at these organisms tells us that the dog is more complex.These are a bit more complicated but I'm actually glad you brought them up: The cocroach falls into the same category as my earlier fly explanation. However, the snake and fish need a bit more explaining. Let's start with the snake because it is the more closely related to us of the two. Well, as I said, the more closely related two organisms are, the more detail we need to examine. An important note here is to understand that we need to look at measurable qualities so we must look at characteristics that are expressed. Snakes (with a few rare exceptions I believe) have only one lung, no fore or hind limbs, and, again with exception of couple bones found in pythons and boas, no pectoral or pelvic girdles. So snakes would be less complex that humnas. (As a matter of fact, I think snakes would make an excellent example of an organism that evolved from a more complex ancestor ( a legged reptile) into a less complex form). As for the fish, we need look no further than the vertebral column itself. All the vertebrae in a given fish are essentially identical cylindrical "tubes", where-as in humans we have cervical, thoracic, and lumbar vertebrae, plus the sacrum and coccyx, each with many processes and grooves and holes included.
I do agree that using the brain as a measure of complexity could present some problems, but I have my suspicions that if we look at the neurophysiology of a dogs brain compared to ours, we would see some differences. Remember, just because something may be difficult to do (after all, nobody said science was easy) doesn't mean we shouldn't attempt it.I guess if my plan is destined to fail, this might be one area that would help it on its way: Hmmm. Help! Actually, it's lunch time for me and I am starving so maybe after I get some food in me I can think about this a little bit more. But hey, if there's anyone else out there with any suggestions...feel free to pipe right in.

NosyNed:Hello again. Sorry I didn't respond sooner but you caught me just as I was headed out the door. Plus, I wanted to think a bit about what you had written. I alway enjoy reading your responses and in this one, you brought up some very good points. Let me take another stab at it. My (initial) measurement is differentiated cell types, and I picked out two just off the top of my head (cardiac muscle and bone) Yes, a fly has chitin. And a dog has: the capability to regulate body temperature internally, three distinct muscle types, two basic types of bone, four different types of teeth (with enamel, and dentin, and cementum), a pancreas, a liver, a well developed immune system, keratin, a four chambered heart, a closed circulatory system (with the associated arteries, arterioles, capillaries, venules, and veins), ureters, a urethra, a blabber, paired kidneys, nine types of epithelium, eleven connective tissues, and a multi-layered epidermis (with its many associated accessory structures), just to name a few things. And each of these is a result of differentiation. I know, flies have some unique structure as well, but (and I can’t say with complete certainty because I am not a dipteran anatomical physiologist) I’d be willing to bet that a mammal has many more specialized cells. But you know what NosyNed, it doesn’t matter. I’m not trying to claim that a dog is more complex than a fly. I’m saying that we can determine which is more complex by looking at differentiation because it is measurable. If it turns out that the fly has many more types of specialized cells...then so be it. Three cheers for the complex fly I wasn’t really clear when I talked about the loss of limbs in snakes and the shape of fish vertebrae. When I said we need to look at more detail when dealing with organisms that are more and more closely related (and therefore more likely to share numerous types of differentiated cells) I went the route of Dan McShea from the University of Michigan and looked at morphology because as he points out, these things can be precisely measured and tested. I guess I wasn’t clear on thatsorry. Also, I don’t care how many bones there are. I looked at the types of bones. If we simply looked at how many, then we would also have to consider that a snake has many more ribs and vertebrae than does a dog. Total kindsnot total quantity. Again, I’m sorry for not being more clear about this, but I usually write too much as it is. I was trying to be concise and instead came off as appearing to go in many different directions.With that in mindwhen you lack limbs and their associated girdles, that’s quite a bit of stuff you no longer have to worry about developing. Bones, muscles, ligaments, tendons, and blood vessels, just to name a few. And if we accept morphology as one measure of complexity, then, with all other things being equal, a tubular body plan is less complex than a quadraped body plan. A one lung system would be less complex than a two lung system. So this is not a bigger is more complex argument (and no, that was not started by me). It is an argument that looks at kinds of things. I never said bigger was more complex, but when considering complexity (at least in biological terms) certainly you would agree that the more parts involved, the more complex. Not necessarily better or more efficient, but more complex. I am not making things up as I go along. I said that as we begin to look at more closely related organisms we would have to compare them in greater detail. I realize (as I look back at what I had written) that I didn't specifically state that I was going to use morphological characters as the basis for these comparisons, but I thought it was self evident...sorry. If they share a lot of differentiated cell types, then what’s left? Well, we should look at the results of this differentiationand one way to do that would be to look at morphology. When a vertebral column consists of cylinders, all of the same basic size and shape, why should we not consider this less complex than a vertebral column consisting of different types of vertebrae that have transverse and spinal processes, transverse foreman, and various articulation surfaces (as well as other morphological differences)?
But let’s step back for a second, and again ask ourselves what it is we are trying to do. We’re trying to determine if evolutionary processes have an inherent drive towards complexity. So we have to decide on what we consider to be complex and what we consider to be simple. These have to be measurable characteristics and therefore they have to be outwardly expresses by the organism. In Gould’s book Full House we get a nice quote by McShea that says: The point is to rescue the study of biological complexity from a swamp of impressionistic evaluations, biased samples, and theoretical speculations, and try to place it on more solid empirical ground. (McShea, D.W. 1996. Metazoan complexity and evolution: is there a trend? Evolution, in press). He chooses morphology as a tool to do this (for reasons I stated earlier.) You’re correctme saying that I wanted to try to "make it simple" was not the best choice of words. But I didn’t mean simple as in easy. I meant simple as in something we can see and measure. Determining the number of differentiated cell types found in an organism may not be simple to do, but it can almost certainly be done. Using morphology as a measure of complexity may not be easy, but again it can be done (and importantly, it can be done repeatedly with the same percision).So let me sum it all up. I think that by initially using differentiation, we can "quickly" separate simple from complex. Then, as organisms get more and more difficult to sort out in this manner, we can look at morphology as another tool to separate the less complex from the more complex. At the same time, keeping in mind that we are only trying to answer this question: Does evolutoiun show a tendency towards complexity? Comparisons between extremely distant related organisms (or very early organisms with more recent organisms) do not really help much in answering that question.

How can we look at complexity? How about this (Personally, I like this one): The complexity of a system is generally acknowledged to be some function of the number of different parts it has, and of the irregularity of their arrangement. Thus, heterogeneous, messy, or irregularly configured systems are complex, such as organisms, automobiles, compost heaps, and junkyards. Order is the opposite of complexity. Ordered systems are homogenous, redundant, or regular, like picket fences and brick walls. (McShea, D.W. 1993. Evolutionary change in the morphological complexity of the mammalian vertebral column. Evolution, 47:730-40. )(as found in Gould’s Full House).
How do we get these parts? We get them via differentiation, which is (as I’m sure you know) the specialization of cells within a multi-cellular organism. Now, if we couple this idea with the morphological study of the structure of these parts, then I think we can compare the relative complexities of two or more organisms. Flight in and of itself does not equal complexity. How does a fly fly? Again, I’m not an expert with dipterans, but I think it's something along the lines of using indirect flight muscles attached to the inner chitinous wall of the thorax. Wing beats come about as a result of distortion of the thorax as the muscle contracts and then relaxes. Is that complex? Well I guess it depends on what you’re comparing it to. For example, if we look at the number of parts involved just with flight, then I think avian flight would be more complex than insect flight. Of course, I don't know for sure that this is indeed the case, but I will say this: If we use the above expanation of complexity (number of parts), and if necessary couple it with a look at their morphology, then we can figure it out. Ok, I mentioned the 4-chambered heart because it has specialized cells. But I also stated that morphology could be used as a measure of complexity. Would you not agree that the 4-chambered mammalian heart is more complex than the tube heart of a typical insect? If we can’t even agree on this, then what’s the point?
But let me say it againI don’t care if a dog is more complex than a fly. It doesn’t matter which is more complex. What matters is that we can determine which is more complex if we look at the number of partswhich came about via differentiation. Will it be easy to determine this? I don’t know...in some cases probably "yes"...in others, probably "no". Could we determine this? I see no reason why we could not.

Hello Again:In reply to my question about the complexity of the mammalian heart compared to the insect heart you wrote: What more do you want me to tell you about morphology? It’s the study of structure. I think the problem comes in when we try to relate morphology with complexity. In that sense then, I look at morphology in terms of its heterogeneity. Although you may intuitively think a mammalian heart is more complex than an insect heart, I say that it is unquestionably more complex, because of its more complex structure. I guess that in a nutshell, I ascribe to the view that when we talk about an organisms biological complexity we are, at least in part, talking about it’s morphological complexity. Does this help clear things up a bit?But I think the bigger question is not whether one part of an organism is more complex then its counterpart in or on another organism, but rather, how many parts does one organism have when compared to another? Can we use parts as a measure of complexity? I agree with others that say yes. The more parts, the more complex. How do we measure parts? We can look at functions (after all, function always reflects structure). Since most parts will not have overlapping functions, the variance in the number of functions for each part will be low. So the number of functions will positively correlate with the number of parts (McShae D.W. 2000. Functional Complexity in Organisms: Parts as proxies. Biology and Physiology. 15(5):641-668). Sorry, but I don’t agree with this statement? I don’t think my definition is based on intuition (actually, it’s not mine per-say, it’s just something I agree with and am apparently doing a poor job of relaying to this site). As I have said before, it’s based on the differentiation of cells that ultimately lead to how morphological characteristics are expressed. How is that intuitive? We can count the parts, and if we still need more detail (or, as in the case of the fossil record where all we really have are the bones) then we can measure many morphological characters. How is that "intuitive"? Yes, that's what we're trying to do (hey, we agree on something (lol )....and I would look for the answer by looking at the morphology of the two organisms. Specifically (in this case at least), their skeletal morphology. I do not know what other type of measure you could realistically use when looking at the fossil record. I don't think that this particular comparison has been made, but other skeletal comarisons have been done and based on that evidence we can say that it does not seem to show a trend towards complexity (see Thomas, R.D.K. 1993. The skeletal Space: A finite set or Organic Designs. Evolution.47(2): 341-360. for more info if you want).So now I ask: How else would you answer a question dealing with complexity between a horse and a triceratops, other than by looking at the fossil record? And if you use the fossil record, what else could you use besides the morphological characteristics of the bones? I haven’t given you just clues on how to get to the answer of: Which is more complex, a dog or a fly?I’ve given you a map and the route on how to get there. Just because I have not driven the route does not mean it is impassable.
To be honest NosyNed, I don’t really have the time, or the tools, or the expertise to drive the route. I have read a few papers and couple of books on the subject of biological complexity and just happen to agree with those findings that say there appears to be no evolutionary drive towards complexity. I guess I’m just doing a lousy job of trying to convey what I have learned. Sorry.Maybe I should just ask you this question instead. Do you believe there is an evolutionary drive towards complexity?
I have stated that do I not beleive that such a trend exists and have tried to explain why I feel this way. I'm curious as to how you would answer the question. My guess would be that you feel it is currently an unanswerable question...is that correct?

Hi Loudmouth:I'm flailing around like a chicken with its head cut off, trying to explain "complexity" and now you jump in with "specialization" as someting new to try and measure and explain! Thanks... lol.As for your thoughts on there being a general trend towards complexity, would you equate that with an inherant drive? I guess I'm asking because I'm not sure what you mean by "a general trend" (and I must admit, that I have used the term myself. But then, of course, I also knew what I meant by it )? My feeling (as I have so eloquently explained in my prevous posts...ha...lol...sorry NosyNed) is that as many organisms evolve "towards" simplicity as evolve "towards" complexity...that there is no directional bias either way.

Yes, loosing complexity is a likely as a gain in complexity. Why should I? What is there about evlutionary theory that would imply that a bias (one way or the other) will occur?

Hey;Wait a minute...I've been pulling out what little hair I have left on my head in an attempt to explain, in a coherant fashion, why I don't think that there is an inherant drive towards complexity and this whole time you have been in basic agreement with me! ()Actually, this has been fun and I must admit that it has "forced" me to better explain my position, which in tern has "forced" me to look at new data as well as refine my ideas. So I guess, that in warped sorta way I should be thanking you. Hey, if I didn't enjoy this, or if I took your criticism personally, I would have left days ago. I'm not sure I agree completely with this. If you look at the "average" complexity, then because of bacteria, we will always get a relatively low number. I think what Gould was trying to say (isn't it too bad we will not get the opportuniy to have this answered by the man himself) is that even if you take bacteria out of the equation, we still see no drive towards complexity. That is, even if we started our investigation at middle lines of descent (the first fishes, the first mammals, the first seed plants, etc), we will see some organisms evolving from that point and becoming less complex while some others take the route towards more complexity.
Or are we again both saying the same basic thing. You in a concise sentence or two, and me in a verbose paragraph? Well, aren't you a bundle of positive thoughts (). I know, extinction is a virtual certainty at some point...but still, I hope it's a ways off yet.

Saviourmachine: You're not really gonna make me go through this all again are you?
My previous posts on this thread have explained why I do not think that there is an inherent drive towards complexity. I use the same arguments to explain why I do not think that there is an inherent drive towards simplicity. So if we don't see a significant difference between the numbers of organisms that are a result of simplification from their ancestors and those that are more complex than their ancestors, by default my position would be that things just evolve. If simplification will solve the "problems", so be it...if complexity is needed..then that's fine too. Either way, natural selection will "make" that descision, and I see no reason to suspect that one route should be favored over the other.

By George...I think we've done it! See, Canadians and Americans can get along, despite the best efforts of "dudya" Yes, I agree that complexity has increased, and that it was a result of the "left hand wall" and not an inherent drive.Whew, that was close! (meaning I didn't have much hair left to pull out).

Saviourmachine:Ok, so in post 86 you said:I guess I'm not completely sure what you're trying to ask here. I interpret this to mean that you think I am claiming there is an equal likehood of either of these "tail losing" scenarios arising. I'll answer this as best I can based on this interpretation.
Specifically, are you asking me (as I see it) if complexity would have decreased in either case, even though one scenario is a loss of information while the other is a net gain? Is this a correct assesment of what you were trying to ask me to address in the above quote?By my assesment of complexity, either route would be considered a decrease. Remember, I am basically claiming that the expression of the genes is what is measurable, not the genes themselves. How can we use genes to measure the complexity of organisms that are extinct and all we have are the "bones"? Plus, tail-loss is readily seen and measurable. How would we deal with other, more subtle changes in an organims complexity if we do not look at the phenotype instead of the genotype (especially if we do not know the loci of the involved genes)?
Let me see if an analogy would help. Let's say I draw up some plans for a way to open my front door without me having to get up out of my chair. I draw these plans with non-easable ink, so if I change my mind on what I want, I have no choice but to alter what I have already written. Ok, so I design this elaborate system of pullies and buttons and switches and alternate tracks that operate such that when I pull a string, a bowling ball is released from some resting point and rolls along these tracks I have built and activates these various swiches and and pullies and alternate routes and eventually it opens the front door by falling on a lever that turns the door knob and opens the door. I use this system for a while but grow tired of the time it takes to open the door so I add to the original plans an alternate route such that the bowling ball simple follows a straight path towards the door, falls onto the lever, which turns the knob and opens the door. I would conclude that despite a very detailed and complex set of original plans and the addition of a novel route, the final outcome would be a simple method of opening the door. Does this do anything to help explain my position? I fail to see why this question will immediately be raised? Why does the speed (rate) of change matter?

Hello Again, nice to here from you: What I meant to demonstrate by the analogy was that even when information is added, it does not, IMHO, necessarily equate to an increase in complexity. In my analogy, I did not draw a new set of blueprints for the new (less complex) route the bowling ball took. Instead, I simply altered my existing blueprints by ADDING a new set of tracks (route). That is, I added more detail to the instructions, which resulted in a less complex system for opening my front door.
Information is usually not lost without a causative agent. By that I mean that an organism will not lose its tail for no reason, or if it does (pleitropy, linked genes, polygenic inheritance, etc) then Natural Selection will decide if that loss was adaptive or maladaptive (via fitness). So it is the outcome that needs to be measured, not the route. Or to put it another way, the complexity of the directions should not be used as the ultimate measure of complexity (perhaps they could be considered the penultimate measure ). Instead, the outcome of the directions is what’s important. If we use information code as the measure of complexity, then we would need to know the entire code in order to make comparisons. Isn’t it much easier to measure the result? But the result is the same. Although I understand your point of view, I think you are headed down a path that is impossible to measure (at least not with the current technologies available). We do not, for example, know the genotype of every extant organism and even if we do eventually unlock this information, we certainly will never ( I know, I know, never say never) know with complete certainty what the genotype of every extinct organism may have been. So how can we use it as a measure of complexity? In your example you conclude that if a tail is lost by removing genetic information, then the resulting organism is less complex than it closest ancestor, but if the tail is lost because new information was added that resulted in a blockage of the genetic code that forms the tail, the resulting organism would be more complex than its closest ancestor. So we would have two morphologically identical organisms, of which one is less complex than the other. Let me push this example to the extremes. Let’s suppose that in a population of monkeys, some individuals give birth to offspring with no tails due to a loss of genetic information, while other offspring lack tails because of the addition of new genetic information. (I'll continue with this rather unlikely example..but only to make a point). Suppose that these tail-less monkeys have an advantage in a slightly different environment, so they exploit this "new" habitat and eventually speciate. Knowing that Natural Selection only operates on characteristics which are expressed and if we further assume that the loss of the tail (no matter "how" it was lost) has no other genetic consequences, then by your measure we would then have two levels of complexity for the same species. Not a very useful tool, I would say. But current plans are based on original plansand if the ancestor we are using as a bases of comparison is extinct, how would we know if the current plans are less complex or more complex? For example, NosyNed stated that the type question we may want to answer is whether a triceratops is more complex than a dog? Using your method of measure, we can’t answer this because we have no way of knowing the coded information of the triceratops. We do, however, have a basic morphological framework from which to work and can look at structural components of each and make an assessment based on that. I don’t necessarily agree that there are two types of adaptations. An adaptation is simply any change in an organism that results in a higher level of fitness, and which was brought about by Natural Selection for its current function. It doesn’t choose the route (be it the addition or subtraction of information), it only looks at the outcome. For example, when we look at evolution as a whole, the complexity we see in mammals is an anomaly (in a sense) and is a result of left hand walls. What do I mean by this, you’re wondering? Well, Gould states that the ultimate left hand wall is that which represents the simplest living organisms (most likely bacteria). Go further left of this wall and you would no longer be considered living. What I am saying is that if we have multiple left hand walls, each representing a lower limit to some arbitrary classification (for instancea mammalian left hand wall which sets the lower limit for what we would classify as a mammal), then if we start at this lower limit and look at the evolutionary history of the organisms within the classification, we would see that some things became less complex, while others increased in complexity. I contend that we would have no idea (in a vast majority of the cases) how the organism got to its current design (no, I am not saying that there is a designer ) and that as a level of measurement, the route is unimportant. Natural Selection does not care how it got there, it only looks at the organisms’ ability to survive and reproduce in its current design, and makes adjustments based on that information.I guess this all means that I think morphological characteristics are currently the best method we have for making complexity comparisons.

Hi Brad McFall: Uh...yeah, and then "Bobs your Uncle"...there ya go.

Hi Brad McFall: Uh...yeah, and then "Bobs your Uncle"...there ya go.Oops...so sorry...I got so excited about finally getting a "Brad MacFall response" that I accidently hit the send botton twice.[This message has been edited by FliesOnly, 02-24-2004]