Evolutionary Theory Explains Diversity

I'll start off with some definition of what we are talking about ... to make sure we are talking about the same thing. In the science of evolutionary biology there are two (2) basic processes:

1. the change in hereditary traits in populations from generation to generation.
2. the reproductive isolation of daughter populations from the parent populations or other daughter populations.

The first is a basic definition of "evolution" (the process that is the subject of the theory), and it is similar to other definitions used, including Darwin's original formulation ("Descent with Modification") and what is often called the genetic definition (the change in the frequency of alleles in a population over time). It is also similar to what is used to teach the science of evolutionary biology at the university level.The second is a basic definition of "speciation" where descendant populations become genetically dissimilar with isolation as time passes due to the process of evolution operating in different ecologies and through different sets of new mutations\traits that arise in populations of otherwise similar organisms, and because of the lack of sharing of those new mutations\traits with the other populations.Each of these processes operate through several mechanisms, some shared some not. Natural selection is one such process, and the one that Darwin recognized as being able to cause descent with modification. Ecological changes are also a mechanism, as evolution is a response system, and populations of organisms will respond to different ecologies with different "fitness" selection.Darwin's insight was that these simple processes were sufficient to explain the diversity of life as we know it

• from life on earth today,
• from history (accounts of now extinct life),
• from prehistory (cave paintings and other archeological artifacts),
• from the fossil record (the natural history of life that has lived on earth in the past) and
• from the genetic record (although he did not know about genes he figured out that there was "a" mechanism that transmitted hereditary traits from one generation to the next, and that populations were related by common ancestry, genetics has just given us better information on what the various mechanisms are and how we can determine the common ancestry history from the evidence in the genes).

This is what the theory of evolution is (as opposed to the process and the science): that these simple processes, the change in hereditary traits in populations from generation and the division of populations into reproductively isolated daughter populations, are sufficient to explain the diversity of life as we know it, from the life on earth today, from history, from prehistory, from the fossil record and from the genetic record.This theory is based on a series of simple basic observations and logical conclusions:

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Observation (1): no two organisms are identical.Observation (2): some of the differences are hereditary (genetic, genotype), some are due to environmental effects (affect development, phenotype), and some are acquired by the organisms (behavioral, learned, individual traits, memes).Observation (3): some (not all) of the difference between organisms enable some (not all) of the organisms to survive and breed better than others.Observation (4): to affect the population of organisms over time, traits need to be passed from one generation to the next.Observation (5): genetic traits are passed by genes, environmental traits are passed by the environment, learned traits are passed by memes.Observation (6): traits not passed on to offspring are lost, whether they are genetic, environmental or learned.

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Conclusion (1): some hereditary traits result in differences that enable some organisms to be better "fit" to survive and breed than the hereditary traits that hinder survival and breeding, and they will become more common in following generations of those organisms, and thus evolution - the change in hereditary traits in populations from generation to generation - will (by definition) occur.Conclusion (2): some traits due to environmental effects result in differences that enable some organisms to be better "fit" to survive and breed than the environmental traits that hinder survival and breeding, and they will become more common in following generations for those organisms that remain in that environment, and also compared to organisms that leave that environment (or when the environment changes).Conclusion (3): some traits that are learned result in differences that enable some organisms to be better "fit" to survive and breed than acquired traits that hinder survival and breeding, and they will become more common in following generations for those organisms that continue to teach them.

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Observation (7): "fitness" selection operates on the individual organism as a whole, on the combination of genetic traits, environmental traits, and acquired traits of each individual organism and the net differential in ability to survive and breed.Observation (8): individual organisms that have a "net fitness" can carry traits that would otherwise be detrimental to selection.Observation (9): hereditary traits, environmental traits, and acquired traits, that don't affect survival or breeding would be neutral to selection.Observation (10): stochastic (chance) events can wipe out individuals, subpopulations or entire populations depending on their (catastrophic) severity.

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Conclusion (4): neutral and harmful traits can still spread within breeding populations, just not as readily as beneficial ones.Conclusion (5): "fitness" is a relative term, relative to both the other organisms in the neighborhood population/s and to the environment/s where each organism lives.

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Observation (11): traits that are a disadvantage or neutral in one environment can be an advantage in another.Observation (12): environments are not static, but change over time due to ongoing geological and astronomical processes.Observation (13): adjacent environments can be similar but not identical.Observation (14): more offspring are usually produced by populations than are needed to replace the current population.

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Conclusion (6): the amount of selection operating on any generation will be relative to the proportion of the population that can be supported by the various environments where the organism can survive and breed.Conclusion (7): organisms that are better "fit" to survive in adjacent environments would tend to go where living was easier.Conclusion (8): subpopulations of organisms in adjacent environments are more likely to breed with other members of that subpopulation than with members in other environments.Conclusion (9): isolated populations of originally similar organisms will over time, generation after generation, become different from each other. After several generations they will have different distributions of genetic traits, different traits due to environmental factors and different learned behaviors.Conclusion (10): when such populations become reproductively isolated, no longer share hereditary traits, they are not restrained from diverging into different forms of organisms as they adapt to different environments.

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By this process diversity arises: populations of organisms spread into different ecosystems, the subpopulations evolve to adapt to their new surroundings, becoming first different varieties, then different species, as the breeding between different populations declines. When populations are reproductively isolated they are free to evolve in different ways to adapt their different ecosystems.The question that arises is whether this process is sufficient on it's own to explain the total diversity of life as we know it, from the world today, from history, from prehistory, from the fossil record and from the genetic record.This, then, is the theory of evolution: This can be tested against the diversity of life: is there any evidence from the vast record of diversity of life that cannot be explained by these processes? So far the answer is no. Note that this is how science operates: take observations, develop conclusions from those observations and then formulate a theory based on those observations and conclusions, and then test the theory.This is NOT how faith operates. Thus science in general, and evolution in particular, are not based on faith, but on observation and logic. Science in particular can be tested and concepts can be invalidated. Enjoy.Edited by RAZD, : added end comments. Edited by RAZD, : replaced chopped off comments at endEdited by Admin, : Change title.Edited by RAZD, : title to reflect focus on diversityEdited by RAZD, : withEdited by RAZD, : updated added reformattedEdited by RAZD, : sub

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This is intended to continue part of the discussion from the "Equating science with faith" to show why it is rather silly to claim one "disagrees" with evolution.

You have a dangling paragraph at the end.If you want the discussion to be about faith in science, it needs to be drawn to it more tightly than just a statement that it's a continuation of a prior thread that was about faith in science. The title should be changed to draw it to that topic, also.It would probably be a good idea to shorten and simplify the presentation by focusing just on evolution and leaving "environmental traits" and memes aside for the moment.

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--	Percy
	EvC Forum Director

better?

Thread moved here from the Proposed New Topics forum.

Thank you. Now we wait for the evophobes to comment?I am particularly interested in AntiLie's reasons for "disagreeing" with evolution.Enjoy.Edited by RAZD, : subtitle

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I am not sure if I qualify as an evophobe, so you may not want my comments. I will attempt to humor you anyway.I would not say that I disagree with any of your observations or conclusions with the exception of conclusion number 5 and your theory. It appears that all of the other observations and conclusions relate to micro evolution.I do not see where your observations and conclusions supports your theory. You give no evidence that your observations or conclusions would allow changes to move between species. It is not sufficient to show that one species can experience changes. There must be evidence to show that these changes can give rise to new species. I don't know that species is the proper scientific jargon, but I think you get the idea.When I was in school they had these pictures of apes evolving into men. If I understand these forums, then that is no longer the accepted theory. It appears that you are proposing that apes and men evolved from something else. They have a common ancestor. To help me along with your observations and conclusions, maybe you can describe how this process worked in simple terms that I can understand. How did an amino acid or a protein with no genetic code turn into an intelligent human being?Or maybe you can give me a link that would show me the pictures of macro evolution that the science world is using today.

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"There is one thing even more vital to science than intelligent methods; and that is, the sincere desire to find out the truth, whatever it may be." - Charles Sanders Pierce

A common analogy when explaining the relationship between microevolution and macroevolution is walking. Each step in a walk takes one only a tiny distance, but one can walk all the way from New York to San Francisco one tiny step at a time. In the same way that the steps in a walk can accumulate into long distances, the small steps of microevolution gradually accumulate into large macroevolutionary changes.The observations and conclusions you're responding to note that because all reproduction is imperfect that genetic change over time is inevitable. There is nothing that can prevent it, and natural selection locks in changes consistent with success in the environment. In other words, there is nothing that can stop the tiny steps of microevolution from taking place, and given that environmental change is just as inevitable the genetic changes will accumulate and eventually take the population long "distances" (genetically) from their original state.A common response to the walking analogy is that macroevolution is actually like walking from New York to Paris - simply not possible. What's missing from this form of the analogy is the genetic equivalent of the Atlantic Ocean.--Percy

Welcome to the fray, Wumpini. Only if you are afraid of learning what evolution is really about.

quote:

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Conclusion (5): isolated populations of originally similar organisms over time will become different from each other. After several generations they will have different distributions of genetic traits, different traits due to environmental factors and different learned behaviors.

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In order to disagree with this conclusion you would need to show that isolated populations can transfer hereditary information, that environmental effects will be transmitted from one population in one environment to another population in another environment, AND that behavioral traits learned in one population can be communicated to the other population, all while they are isolated.Disagreement is not just refusal to accept evidence, you need a reason to disagree.

quote:

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Theory: this is sufficient to explain the diversity of life we see in the world today, in historical accounts, in the fossil record and in the genetic evidence.

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The real question is not whether you agree with the theory or not, but whether you can invalidate it: can you demonstrate an instance where it is not possible to explain the diversity of life by the accumulation of changes in hereditary traits in populations from generation to generation? And now we ask the question of what is microevolution and what is macroevolution? Perhaps because that does not happen? What if I said that all evolution occurs within species? Species is the correct term, and what you are talking about is conclusion (5) again: daughter populations that become different over time to the point that, when they interact, they do not behave as one species but two, due to accumulated differences. See Asian Greenish Warblers for an example of how little change is needed for this to occur.One of the questions, though, is how much change is sufficient to demonstrate this? The currently accepted theory is that apes and man evolved from a common ancestor that would be classified as an ape (as is man, btw). See hominid skulls. Interesting question. Do we know that it did? If it did not happen, would that mean that life can't evolve? And one of the important questions is how do you test for truth?Enjoy.

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The topic is evolution is simple. I still have many questions before I can be convinced that evolution is simple.I still do not understand how the changes can cross the lines of species. I will have to study more on the subject to see the line of descent that is being proposed. Where exactly did man come from? Why are there not abundant transitional forms in the fossil record? How did the reproductive system evolve? How did complex structures such as the eye and ear evolve when they require all of the interrelated parts? I agree that small changes can occur over time. I also agree that given enough time these changes could be significant. However, these small changes cannot account for the creation of systems that are extremely complex and have interrelated parts.I know that evolution does not take into account the origin of life, but that needs to be considered also. Without life in the first place, there can be no evolution. If we are going to attribute supernatural causes to the origin of life, then we need to consider that there could have been supernatural causes throughout the process.It is past midnight in this part of the world, so I will have to continue this discussion and study tomorrow.In the local language of Dagbani here we would say "Nawuni ti gom." May God give us sleep.

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"There is one thing even more vital to science than intelligent methods; and that is, the sincere desire to find out the truth, whatever it may be." - Charles Sanders Pierce

There is no such thing as "lines of species". In the same way, there is no such thing as a line that seperates New York from LA.You're still thinking like a typical creationist where you think in order for speciation to happen a creature has to morph into another.Just think back to the walking analogy for a few minutes. Where exactly do you stop being in New York AND start being in LA? If you haven't noticed, this is a nonsensical question. This question assumes that NY and LA are right next to each other. But instead, the two places are seperated by a large distance that CAN be crossed by accumulating lots and lots of tiny steps.In the same way, your comment about the supposed "lines of species" makes no sense. There are no such things as lines of species just like there are no such things as lines of colors in the light spectrum. If you are going to seriously study the subject, you must first clear your head of creationist propaganda. There is no distinction between macro and micro evolution except for the time that's involved just like there is no distinction between walking to a few paces away and walking all the way from NY to LA. One requires a lot more time than the other. However, they both use the same mechanics. When I referred to creationist propaganda, this is one of those propaganda.Every fossil that has ever been found IS a transitional fossil. Try not to think of evolution having a goal of morphing one creature to the next. Rather, each tiny mutation coupled with natural selection gives changes to the allele frequency of the population. Over a large amount of time, the change in allele frequency could amount to something that would be unrecognizable if we compare the allele frequency to the one we started out with.In other words, you will never find a fossil of a creature between a duck and a croc. This is the most common creationist strawman.Going back to our walking analogy. If you are to walk from NY to LA and you decide to take a picture of yourself at random times. Each snapshot represents where you are from NY to LA, but by just looking at these snapshots it is next to impossible to say for certain which route you took to get from one place to the next.Each fossil is a snapshot in time, nothing more. Each one represents the creature of the particular population when the allele frequency is exactly where it was.The other thing is you have to understand that fossilization is a rare event. What is even rarer is them surviving millions of battering by natural causes. And what is even rare than that is us finding them.Take the do-do for example. We haven't a single fossil of the creature and we know for sure they once existed in great numbers. The passenger pigeon once dominated our skies. They numbered in the hundreds of millions. They're extinct now. No fossil at all. I can point to a dozen other examples off the top of my head of creatures we knew to have once existed in great numbers but are now extinct without a single fossil. In tiny changes through mutation and natural selection that took place over a billion years. Can you name a mechanism that would prevent large changes by accumulation of lots and lots of tiny little changes? This is another common creationist tactic. Look, even if tomorrow the Almighty comes down from heaven and told us he poofed everything into existence 4 and a half billion years ago, this still doesn't disprove evolution.By the way, "goddunit" is an intellectual dead-end. How do we account for the motion of the planets? Goddunit! How do we account for lightning? Goddunit. How do we account for fire? Goddunit. How do we account for lunar and solar eclipses? Goddunit. I can go on and on until I turn blue. Do you not see the obvious intellectual dead-end?

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I'm trying to see things your way, but I can't put my head that far up my ass.

The answer is simple: they don't. If you think this is part of evolution, then you need to revise your thinking. Why? Consider that life was created, but it was simple single cells: what prevents evolution from occurring after this point? Why? We can even consider that the universe was created in a way that life would develop naturally.Further, how does this prevent evolution from occurring? There are. Practically speaking all fossils are transitional, as they all show features intermediate between ancestor species and daughter species. Why not? What prevents it? Do you know how many different kinds of eyes exist that show intermediate forms from light sensitive patches of skin to eyes capable of seeing 6 primary colors and focusing on mice from hundreds of feet in the air?You wanted to see a picture of macroevolution. In one very real sense this is one:http://biology.unm.edu/...iology_203/Summaries/Phylogeny.htm

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Phylogenetics- a discipline of evolutionary biology which seeks to accurately depict the evolutionary relationships among living and non-living taxa.

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Taxa are best classified according to monophyletic groups, or clades. In these monophyletic groups, an ancestor (node) and all descendents are included. For example, “mammals” are a monophyletic group when we include the most recent common ancestor (MRCA) of all known mammals.

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Humans are a third chimp
DNA homology suggests that humans are more closely related to living chimps than either are to other living primates.

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It also answers your previous question about human evolution. Each branch shown is a speciation event, where two (or more) daughter populations no longer interbreed with each other, and thus are free to evolve separately. Each line after branching represents evolution within each lineage, the change in hereditary traits in populations from generation to generation.Macroevolution is the divergence of populations after speciation has occurred, they are still related by ancestry to their common ancestor, but the evolution within each daughter population allows them to diverge - sometimes a lot, sometimes a little.Macroevolution is really nothing more than the structure of life due to common ancestry and the divergence after speciation, with changes caused by microevolution.Enjoy.

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Thread moved here from the Is It Science? forum.

Hi RAZD,I've moved this thread back to [forum=-25] because what I feared immediately came to pass. If the focus of discussion is faith in science, that's fine. But if the focus of discussion is evolution, then this is far too broad a topic. For example, Wumpini asks about transitional forms, the evolution of reproduction, eye and ear evolution and the evolution of complexity.You need to either clearly focus the discussion on faith in science, or narrow the focus of discussion sufficiently so that this thread doesn't wander over all aspects of evolutionary theory.

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--	Percy
	EvC Forum Director

I agree, this needs to refocus. I think it's going to be difficult to keep new people from going there initially, the question is whether we can get them to address the OP directly without it. How about the Biological Evolution forum then?We can stipulate that it is not about origins or the evolution of eyes or any specific features, just the simple process of changes to hereditary traits in populations from generation to generation leading to diversity.Perhaps a discussion of what diversity means is appropriate.Diversity Definition & Meaning | Dictionary.com

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di·ver·si·ty n. pl. di·ver·si·ties
1.
.. a. The fact or quality of being diverse; difference.
.. b. A point or respect in which things differ.
2. Variety or multiformity: "Charles Darwin saw in the diversity of species the principles of evolution that operated to generate the species: variation, competition and selection" (Scientific American).

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American Heritage Dictionary 2008

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Diversity is just difference.Once you established that evolution - the change in hereditary traits in populations from generation to generation - causes continual change based on survival and breeding or organisms in a continually changing world, the question becomes how you generate two different populations from one parent population.Once you've established that it is possible to generate sufficient difference between two isolated populations of related organisms to the point they no longer interbreed -- the P. t. viridanus and P. t. plumbeitarsus varieties of Asian Green Warblers (Phylloscopus trochiloides), for instance -- the question then becomes how much difference is necessary to generate all the different forms of life we know.This gets down to the question of how much difference will satisfy the creationist.Thanks.

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