Wednesday, May 11, 2005

A (Very) Brief Overview Of Evolution

Since there seem to many misconceptions about what evolutionary theory is or is not, and what has and has not been found so far, I feel like now is the time to explain it. There are more complete explanations than mine, but this is meant as an overview to answer some of the misconceptions.

First, evolution refers to change over time, generally millions of years to speciate (evolve from one species to another genetically incompatible species). Start in your head with one species spread out over a large area. In any population, selection pressure is present for more desirable genetic traits, in humans too, but when times are good and most of the population is able to reproduce, there is little reason for small differences caused by mutations to become the norm in the gene pool. The mutations are just folded into the normal population and you can have all kinds of variance. For long periods, there will be no evolutionary reason to change. Then there will be a physical barrier that will impede the exchange of genes across the entire population. We see this sort of thing all over the world today. Marsupials are almost entirely confined to Australia for instance. They happened to go in that evolutionary direction based on pressures found on that continent, whereas elsewhere it did not happen. The barrier can also be distance. If the range for a species is extremely wide, the same effect can occur.

Then, disaster strikes, as it does with regularity on Earth. An asteroid hits, the climate changes, a new predator moves in, or any number of other calamities, and the existing species or portion of a species must adapt or die out. Suddenly, the little differences aren't so little any more for at least one part of the population. The longer-legged creatures will run faster, and predators will eat the shorter-legged ones instead. The climate gets colder and suddenly longer fur is a real life-saving asset. Genes that were once scattered in the population are now heavily selected for, and the look and genetic makeup of the species can change quickly and dramatically. If there are enough genetic differences in the population over a long enough time, genes between the two of them become significantly different in length or structure. Fertility between the "old" and "new" forms suffers, and eventually they are so different that fertilization is impossible. We see the early stages of this in modern day horses and donkeys. They are similar enough to breed, but not enough to produce fertile offspring. There are other examples especially in birds where there are similar phenomena. Lions and tigers can breed, but the fertility rate is not the same as with the original species. We can see these various stages of speciation.

Speciation can result in many different outcomes based on what fossil evidence and genetic analysis tells us. Parts of the population could die out, leaving another part under different pressures unchanged. Two different species could result from one. One different species plus the original species could remain. The entire species could evolve into another. The whole species could die out and not be replaced. All of these scenarios can occur.

One logical fallacy that is often presented is that it is impossible to reproduce speciation in a lab environment. Yes, it is true that we do not yet have either a time travel machine or a time speeding machine where we can see what happens over millions of years in a bottle. We see all of the necessary phenomena that I have outlined in various stages of action, in the lab and in nature, but in terms of evolution, humans have only existed for about the blink of an eye, and you are asking for us to reproduce millions of years in a few decades. We aren't completely there yet, but it does not mean that it's "impossible". All of the individual building blocks necessary are there for speciation to happen, and observable. We just can't speed up time.

Another fallacy also presented is that there are no "missing links". Due to the selection pressures necessary to cause speciation, the "transition" period is pretty quick geologically speaking, about what would be expected from a quick extinction or adaptation to a (relatively) sudden change. The environment is generally similar for a long time, and a sudden shift makes the process accelerate. Without genetic material or any soft tissue at all for that matter, it is very difficult to prove beyond a doubt that something is a transitional form, but we do find these forms on a regular basis. Certainly for humans in this case we have more evidence than for many other animals. Cro-magnon man, Neanderthals, and other types all made an appearance, leading to where we are today. Cro-Magnon man especially were actually quite similar to us. Neanderthals quite a bit similar as well, but probably not enough to reproduce with modern humans. Even just yesterday another portion of a "missing link" was found.



This brings up the issue of "halves are useless". Evolutionary cul-de-sacs are everywhere. We still have an appendix. Ostriches still have wings. So do kiwi birds. Bulls don't need horns in order to survive any more, since they are domestic, but it doesn't mean they disappear. They are not selected against, so they continue. The eye is a frequently used example in the opposite direction. What good is half an eye? Not much. However, each form comes from the last form, so of course the more "advanced" form is heavily selected for, and the old form dies out. If the change is not a good one, it won't last long. People that throw out analogies like a watch randomly coming together from nothing are posing the question as if that is what evolution is. It is not. It goes from one functioning unit to the next. Those that do not function are selected against.

There is much, much more to this, and far more detail than I could possibly put in one post, but at least this is an overview. Post some of your objections if you would like and I would be happy to answer as best I can.

Update: Nicnerd IMed me from his conference and told me there were "truck-sized" holes in my post, and mentioned that there are shell fossils in the Himalayas. Interestingly, that particular fact is something touted by "Young Earth" proponents, which Nicnerd is not. I'm not sure where he got that info. His fact is correct. The Himalayas were formed around 25 million years ago when continental drift shoved the Indian plate into the Asian plate. The land portion of both of these plates were underwater at one time, when "shells ruled the Earth". This was from around 300 to around 450 million years ago, roughly. Shells in the Himalayas? We should expect nothing less!

10 comments:

Steve B said...

Erik,
You say that while reproducing speciation is the lab is not technically impossible, it has not yet happened. That is essentially my point. You cannot validate this theory with empirical testing. So why is it treated as immutable law?

Most of my post dealt not with the specifics of evolution, but rather, with what I see as an unscientific approach to evaluating the available data in only one narrowly pre-defined context.

The question I have with catastrophism and the survival of optimized variants lies in what proportion/percentage of any population has a certain aberration? If some environmental change occurred which determined that only red haired, left-handed people shorter than 5'6" tall survived, are there enough of these variants in the population to continue to reproduce at a level that will ensure survival of the species? And even if there are enough total numbers, are they geographically close enough that they would be able to find each other, band together in community, and sustain themselves?

To me, one example of "evidence" for ID are the phytoplankton and other little "machines" with interoperating, cylcing, self-repairing "parts." To you, this evidence is not incosistent with evolution, and so you dismiss it as support for ID.

Thus validating my point.

Erik Grow said...

1. Reproducing speciation has not yet fully been done. It does not mean impossible by any stretch. Evolution as a whole is not immutable at all, but nearly every basic component that facilitates it is provable.

2. How would you evaluate the current data differently?

3. You are quite correct on that. There are numerous examples among dinosaurs and other species that are not able to adapt quickly enough, or as you say simply do not have enough of the necessary characteristics in the gene pool to make it. Species die out all the time. Evolutionary cul-de-sacs occur all the time, or there could be rodents the size of bears grazing in your backyard instead of woodchucks. ;-)

4. Hmmm, so you are saying since evidence can be interpreted as both, that it supports both. You are partly right. The basic problem with ID however is that it is also impossible to DISprove. Everything could be seen as evidence for it, because it is impossible for there to be evidence against it. In order for science to be tested, there has to be some kind of true/false test available of some aspect of it. What evidence could anyone ever produce in order to disprove ID? Even if I could prove that speciation definitely happens now, which we see abundant signs pointing to, but no time machine to prove beyond a shadow of a doubt, that still doesn't prove that is how we got here. This makes it faith-based and dependent on divine intervention, which makes it not science. It doesn't make it automatically wrong, but it is why it does not belong in school.

There are any number of different ways that evolution *could* be discredited. You could prove natural selection doesn't happen. You could prove mutations and natural transpositions of genetic material don't account for enough change to speciate. You could prove that all animals lived at the same time once.

Steve B said...

Proving a negative is always problematic. Prove to me God doesn't exist?

There is a great deal of evidence, in many analysts' minds, which causes serious problems to evolutionary theory. But because we can't consider ID as an alternative, due to it being solely theologically based (as you have repeatedly restated), then the evolutionists answer is, "Well, we just don't have all the pieces yet. But we will! And how dare you question my data! Do YOU have a PhD in MicroBiology. HAH! Didn't think so! Shut up."

If you can reproduce a spontaneous accretion that results in a self-sutaining organism from disparate parts, then you will have taken a large chunk of the wind out of the sails of those who say it just couldn't happen. Go ahead, I'll wait.

I guess part of my resistance to evolution is the simple mathematical improbability of all those necessary sequential actions happening spontaneously and randomly, and continually happening in just the right order, with just the right conditions, time after time after time.

To me, this stands out as every bit as much of a "leap of faith" as that you ascribe to creationists.

{{shrug}}

Erik Grow said...

1. God existing or not has nothing to do with evolution.

2. Evolutionary theory has a great deal more of the pieces than you seem to think. All of the individual pieces necessary are very much observable and testable. You refer to it as a "theory in crisis", but I have not heard of any evidence that has refuted any of the research I have talked about here. If you want to believe ID as an alternative, that's fine. Nobody says you have to believe anything is correct, no matter how much evidence is behind it. I'm still waiting for research for ID or against evolution.

3. This is not necessary at all for evolution. All intermediate stages are viable. You are essentially saying that your mind would be eased if evolution were to explain something that it does not require. Your statement indicates that you don't understand evolution very well, no offense meant.

4. This is another common objection to evolution, one that nicnerd and others I think share as well. It is however, not an obstacle, and I can explain why. You are thinking of it in terms of the way things are today being the only or the optimum way that they should be. There are numerous other directions that evolution can take things to overcome the same problem. Longer fur, migration, hibernation, larger size, and more are all solutions to the problem of cold climates. Whichever viable option surfaces in the population first will eventually be dominant. You are also again thinking of things in terms of there never being a pre-cursor to the complex structures that you see in the world. There is also no set order as you are hinting. You are only seeing what HAS happened, not the hundreds of different ways that things COULD have happened.

Devo said...

I'm always surprised at how stridently proponents of both ID and evolution cling to their view of "truth" as they see it. Niether side seems willing to accept the fact that both theories are in development, at least during conversations with each other. Personally, I see both theories as incomplete, and most likely connected to one another in some way. One of my favorite modern-day philosophers, Ken Wilber, said once that it's probably just as likely that anyone is capable of being one-hundred percent wrong about anything as it is likely that anyone is capable of being one-hundred percent RIGHT about anything. Therefore, there's gotta be a grain of truth in just about any theory ever presented by any human. Of course, that's not to say that everyone is right all the time... quite the opposite. Some of the grandest theoretical blunders in history have been at least based in some sort of fact (or, since I have a bit of a problem with the word "fact", perhaps I'll say "rightness" or "truth")...

Anyway, as I was saying, I think ID has some interesting points, though in my opinion, it imbues the universe with a bit too much intentionality for my comfort. I do believe in some sort of animating sprirt driving the development of the universe as we know it, but I don't believe this godhead or whatever you want to call it has the all-powerful, intentional consciousness the ID folks want to attribute to him.

Along the same lines, I don't believe that evolution is the blind game of chance that most Darwinians have come to believe. THat's not to say that specific mutations or genetic developments are pre-meditated in any way shape or form, but the path of evolution has certainly developed into an identifiable *path* rather than a series of random successes and failures. Again, that's not to say that the path is already cut for us, and we are headed toward a great, bearded father figure in the clouds, but the path we have left behind certainly gives us a legacy upon which we are currently basing all steps forward. I would argue that this simple fact almost imbues the forward motion of evolution with a certain sense of "intelligence" though it bears no resemblance to the intelligence we would use to solve a math problem. Finally, I would point to another simple fact that I just mentioned. Evolution always moves *forward*. I've never seen devolution. At least as far as I know... And while that doesn't necessarily point to an "intelligence" in the driver's seat, it certainly indicates that completely random chance isn't in the driver's seat either...

Bottom line is that in my opinion, both theories have their good points and their weak points, but at this phase of development that our culture is currently in, teaching evolution in schools is certainly the more responsible method of raising our children. Teaching it as gospel, however, is probably just as dangerous as allowing the Fundies to teach their version as gospel. Closing minds rarely works well if forward growth is the desired end result...

OK, I'm done ranting... thanks for listenin'!!!

Erik Grow said...

Certainly that makes sense to teach the whole thing, what we know, and what is still not known.

I do not advocate holding up the current model of evolution as the only and ultimate truth, but it certainly has the most evidence so far.

Steve B said...

Got to give a rousing golf clap to Devo. You have managed to state most of my position in a way that I am apparently unable to.

Erik, guess I'll go point by point as well.

1. It is a commonly accepted view that you can't prove a negative. I was merely stating one of the prevailing examples.

I'm actually fairly well-informed on the subject, although I do not have a degree in some macro-biological something or other. I certainly could brush up on some of the details, but I do follow the issue as time allows.

I somehow cannot seem to communicate to you that by refusing to consider existing evidence as potentially supporting ID, simply because of the theological implication, you are not being intellectually honest. Devo said it better than I. If not evidence is allowed to support ID, then by defintion, it never will.

2. I am NOT saying arbitrarily discard evolution in favor of ID. Teach only ID and ditch evolution. Turn the tables,etc. No, no, no. I AM suggesting that evolution fails to answer enough of the questions out there that it should remain under serious scrutiny, and be tested against other theories. I fully acknowledge that a great deal of meaningful and excellent scholarship has been committed to evolution. I don't mean to suggest that it's all just a bunch of hooey. I just don't think it should be the only flavor in the milkshake!

Please answer this question: Why does consideration of an external creative force automatically make that viewpoint unscientific? Who says?

3. "All intermediate stages are viable". This is a non sequitur. Or at least, it is circular reasoning. Only those intermediate stages which were successful, were viable. They have to be viable in order for them to be considered intermediate stages. Otherwise, they are stillbirths, or lunch for predators, etc. Yes?

4. This is adaptation within a species or genus. I don't have a problem with that! It's how you get from a sheep to a seagull that is problematic! This is survival, not arrival.

The theory of evolution requires that a spontaneous, unguided event (or series of events) results in an entirely new species. Birds have hollow bones. Lizards don't. Evolution would have us believe that this transition was made spontaneously, in reaction to changing conditions. By what mechanism? Natural selection? It is my view that this is an inadequate explanation. You don't agree. Oh well. Why does that make me unscientific, whereas you remain in the bosom of empirical analysis?

Your view seems to be that because I am questioning aspects of evolution, then I must not understand it well enough. This is sort of the view liberals take with socialism. Or the Bush election.

"If only they were better informed, they'd see it my way."

It's quite possible that I have examined the same data as you, and come to a different (and potentially equally as valid) conclusion.

Devo said...

Hmm, I hope I didn't come off as a proponent of ID or a detractor from evolution... Perhaps I should more concretely state my position:

I believe that the theory of evolution is the most accurate model we have yet proposed to explain how life arrived at the present iteration we are now present for. However, it is (as PP has observed) incomplete. ID, as it stands, is pretty unscientific in that it does not propose a hypothesis against which any sort of injunction or rigorous experiment can provide any sort of insight. Perhaps I haven't explored it enough, but from what has been presented to me, it is basically a pile of "maybe"s and "well, evolution can't explain THIS... so it must be flawed, and here's the solution"s. If someone can paint a picture of how the scientific method has been used to validate any aspect of ID, I will be humbly corrected.

Now, I DO believe that aspects of ID can be incorporated into evolution. For example, just because "natural selection" tends to favor well-put-together organisms over clunkers does NOT mean that no exploratory "force" is behind the manifestation of hollow wings, for example. I will reiterate that I don't think it's rational or reasonable to assume that this force has some sort of consciousness of its own, or that it's "working toward a goal", because that's simply anthropomorphizing the universe, which is absurd, in my opinion. I think those who imbue evolution with the sort of ID, forward-thinking intelligence are looking at it somewhat backwards. Take culture, for example. We can look back on European and American history and identify a specific series of events that seemingly formed a coherent, intelligently designed story. However, I would posit that none of the Founding Fathers could have predicted the state we now find our country in. ID (from waht I know of it ) presupposes an omniscient consciousness driving the development of species, which I belive is about as plausible as George Washington forseeing computers.

Anyway, if we take a different view, one that relies on existing conditions forming the parameters upon which each subsequent step must be taken, then not only do we have the intelligence posited by proponents of ID, but we have the sort of trial-and-error and survival of the fittest demanded by evolutionists. It's just an acknowledgement of the primacy of cause-and-effect coupled with an understanding that once a complex system has been built up to a point where it becomes more or less self-directed, that system's entire history almost becomes in intelligence in and of itself, simply because there's nothing random about the direction it has taken. Some steps can be logically ruled out as possible and other steps can be inferred simply based upon the steps that have come before. No intentionality, no intelligence (as we conceptualize it, at least, as pre-cognizant and anticipatory) is necessary.

Steve B said...

"Hmm, I hope I didn't come off as a proponent of ID or a detractor from evolution... "

No, I was merely applauding for being willing to admit the possibility of alternate explanations.

Devo, at first you oppose "anthropomorphizing the universe", but that is essential what you are doing in your last paragraph.

You describe a guiding, directive for, but give it no will, purpose, or awareness of what "it" is doing.
Are you saying that because a body can heal itself of injury and replace lost cells, etc., it is because it recognized the need to and so incorporated the necessary functionality in its makeup?

My position is that simply because evolution is A possible explanation, doesn't by definition make it THE ONLY possible explanation. But too often that is how evolution is presented. I just have a problem with that.

I will freely admit you can't readily quantify a "God Force". You can't reproduce creation ex nihilio.

But, when you can't reproduce a spontaneous acretion of elements to produce a single strand of DNA, or the gelling together of one mitocondria, despite carefully controlled, managed, and optimized lab conditions (that pesky external force again), then I suggest that one would eventually be faced with the unavoidable conclusion that something else is going on besides random chance.

But that's just me being my unscientific self again.

Erik Grow said...

The problem as I mentioned for much of this is the problem of time. There just isn't enough time to prove beyond a shadow of a doubt, at least so far. Nobody can force anyone to believe anything else. On to a new topic, once I decide which one to write on.