Evolution and complexity

Unfortunately I haven't been able to find anything on the web that goes into complexity the way I want. I have read a bit of material on it. The problem, as I see it from that reading, is that it is not all that simple. It isn't easy to find a good, quantitative definition of complexity that also feels right intuitively. That is a pretty good idea, I think. It is something that brings it down to a, maybe, measureable, thing.However, the measureing may be hard. It is not immediately obvious to me that a dog is more complex than a housefly. By this measure they may well be the same.We do know that we would like a definition to give us some complexity at least because of our brains which we would like to define as complex. However, does our brain consist of 1, 3 or dozens of diferentiated types of cells. (It sure seems to be more than 1). Is the number more than the number in a dog, snake, fish or cockroach? That I don't know.Your idea works if you step back far enough to have a kind of big picture view of things. But that still won't be enough to tell us whether there has been any increase in complexity for the last, say, 100 million years (or maybe even the last 300 Myr).

But a housefly has chitin which a dog does not have. This is why a "cursory glance" just doesn't cut it. I do not know which is more complex by your 'diferentiated cell types' idea. At my cursory glance I would expect to see a housefly and a dog being very close in complexity."by my measurements" --- what measurements? All you have so far is a 'cursory glance'. Nope. Your own measure is of number of different kinds of differentiated cells. Boas have bones, you didn't say it mattered how many. This is slipping back to the bigger is more complex argument that you, or someone, started with. Snakes have lungs, we do too. Snakes have heat detecting pits, we don't. So far they are equal to us. What does the shape of the bones have to do with complexity based on the definition we have, for the moment, agreed to explore. You are making up new things as you go along. My suggestion would be to do some research into what work exists on the definition of complexity first. Then see if there is any on 'biological complexity'. I know there is some general work done but don't know where.The other choice would be to fall back on 'information'. However, I think that this is clearly inadequate. Random 'information' isn't what we want to talk about.You could perhaps also try to explain where you want to get too.If it is to discuss the nature of changes that can be produced by evolutionary processes then we can see that any definition you are likly to come up with will be producable by those processes. We see living things as one test of this and we can simulate the processes with computers and see changes that will probably match whatever you come up with.You seem to think this is simple. I'm sure know expert but what I think I do know is that there is a whole lot to know and understand. It is not simple. To try to make it simple will be a futile exercise.

And a fly can fly! Where is this getting us. I don't even know how to count "cell types". You are mixing in things like 4 chambered heart etc.I agree that a dog appears to be, intuitively, more complex than a fly. But that doesn't get us anywhere until we have a lot more precision in what complexity is measured by and real measurements of it. Again, at first glance, that seems an intuitively reasonable position but I don't think it is by any means a given. You are counting organs now not differentiated cell types. Let's have just one definition. Could you explain morphology in more detail please? Yes, but it is just a rough and ready, intuitive thing. Now the hard slog has to happen where someone gets down and does the numbers. Of course, right off the bat someone has to tell me how to tell when two cells are differentiated and when they are not. My guess would be that there will be places where that isn't perfectly clear either (maybe not though, I dunno).[This message has been edited by NosyNed, 02-18-2004]

Yes, I would. But so what? My intuition may say the same as yours. You didn't tell me clearly what morphology was but I guess it would say the same thing.So far the definition you want is something that we would agree is intuitively "more complex". But I thought we were trying to answer a question like "Is a horse more complex than a triceratops?" We want to do that to see if we can say if 'complexity' has increased or not over time. So far you've given me clues as to how I might decide if a dog is more complex than a fly (but not for sure). That isn't all that helpful. [qs]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).

Yes and no. (to continue to be a bit obtuse )I am of the opinion that, as Gould has said, that there is no 'drive' at all. However, given a wide variety of empty environmental niches the evolutionary process will fill them and this may produce an overall increase in complexity (however, you define it).There is still room to argue. I rather like the arguement that Gould put forward in "Full House". If I choose what I count in some ways then, from a numbers point of view, there hasn't been any really big increase in complexity.That is, on average, the complexity of individual living things on earth is still around that of a bacteria. This would be calculated by taking a measure of the complexity of each organism and adding them all up and deviding by the total number of creatures.My conjecture is this: If a bacteria has a defined complexity of 1.00 then the average complexity of all life currently on earth is about 1.000000001. That is, other than a bias towards ourselves, life is not more complex than it was a couple of billion years ago.That is an approximate paraphrase of Gould's suggestion in "Full House", I think.Another thing to measure is the maximumly complex single organism. This is another extreme. In that case, the complexity (based on a bacteria at 1.00) is probably over 1,000,000. However, whether or not that has changed all that much recently is less clear.It is possible that a triceratops has a complexity of 898,456 and a horse of 897,923 and we have a complexity of, say, 1,234,582 and a chimp of 1,233,921. In which case even by this extreme measure complexity isn't increasing all that fast over the last few 100 million years.Just as in a Drunkard's walk random processes can appear to be moving in a direction. Specifically when there is a bound on one side. It is not at all impossible that the trend in complexity over the next 1,000,000 years ( a short term thing) will be downward. If we are complex (as given above) then our extinction will reduce the maximal complexity a bit. In addition, the reduction in number of species occuring now must decrease the average complexity by a smidge too.

That is a separate topic. We are discussing whether the evolution of life has a tendancy to increases (or any change for that matter) in complexity. The origin of life may or may not be considered to be a quantum leap in complexity. It is after that has occured that we are interested in here.

The example is at too high level. What mutation would cause the addition of a tail?There are single base pair changes (insertion or deletion or substitution mutations). If such a change results in any decrease then the oposite would be an increase.Why would any on of those single base pair changes be more or less likely than any other?

Reread the topic title again: "Evolution and complexity.
In this context 'evolution' is a short form of the Theory of Evolution of Life and it's diversification. We are talking about life.We should stick to that since we can say nothing about the other step as we don't know what it was or how hard it is or what the change in complexity would be. Again, I think you are right to say the jump to life from non-life is an increase in complexity. But until we define complexity precisely I can't say anything about comparitive changes.Since we don't know the process to get from non-living to living we also can't say how big the complexity jump is.In fact, today, we can't seem to settle on an agreed line where nonliving leaves off and living starts. A prion is pretty complex but not all that complex (is it alive?). A virus is more complex, is it alive? (many so no). A bacteria is definitely alive ( right?). How much more complex than a virus is it? Is a horse a smaller amount more complex than a bacteria is to a virus? I don't know yet.

I think we are agreeing. That is, there is no drive towards complexity. We are also, I think, agreeing that complexity may well have increased. Cetainly if you go back far enough. It is just that nothing is pushing for it. It has occured because of the circumstances of history.

I shaved mine off last week. What are you worrying about?

(an aside, don't use 'drift' in this context, it has a special technical meaning that doesn't really apply here (or at least is a detail we don't need to touch here ))Obviously, the speed varies with the circumstances. Natural selection can, under the right conditions, restrict change. Under those circumstances we may get only a few complexitrons per millenium. Under other conditions, say after the KT boundary there are lots of niches open and changing conditions. We may get many complexitrons per millenium.(I'm playing with 'complexitrons'. I think the correct term is darwins isn't it? )To ask this quesion implies some idea of direction at all. There isn't any. Each creature is, in some way, different. Each reproduces more or less successfully. Depending on the conditions and how they change with time there may be what looks like a direction from this or may not.

I'm not sure how well founded any rates are. I think there is some reason to treat them as more than speculative.

The correlation between the genetic differences and the fossil record wouldn't work so well if there wasn't some constancy of rate would it?In addition, what is understood about the mechanisms suggests that there is no reason to think that the rate wouldn't be reasonably consistent.