Hi Bgood and thereal,
I want to clear up what seems to be a misunderstanding between us. I never asked for a justification of evoluntionary theory, I'm familiar with the theory. My request was, in response to the statement that the theory of evolution is easly testable, to show how one of the theories building blocks, natural selection, can be tested. To date, it is my perception that we seem to be making no progress towards an answer ot my request. It may just be my stupidity, and you guys need to explain it to me again, if you feel that you have already done so.
I understand how evolution is supposed to work, and repeatedly explaining to me how it is supposed to work, does not answer my question. If I'm not mistaken, testability is closely related, even synonymous, with falsification. All I'm asking for is how natural selection can be falsified then, by implication. If natural selection is part of the mechanism that leads us to see the diversity of life today, how can that be tested, across phyla, species and through biochemical pathways? How do we reconstruct the evolutionary history of an organism step by step, showing that by small incremental changes it came to be what it is today, what were the starting points such as the common ancestor, how much and what morphological etc information was encoded in its DNA, what were the incremental changes over what time periods, what were the environmental pressures that caused those changes, what benefits did the organism gain from those changes in response, how and why did those changes survive to form more beneficial traits later on if it added no immediate benefit to the organism, and then, how can that history be falsified? What else is there that that specific history can be tested against? What would be the other options that leads us to believe that our specific history is the correct one, caused by what we say caused it, namely natural selection? Is there any way in which you can show that no conceivable biochemical pathway could have lead to that result?
Since we have had mention of the deer and mouse on this thread, please feel free to show the evolutionary pathway of either in terms of my above request, so that we can arrive at a model that can potentially be tested/falsified.
Now on to the responses I received, although due to our misunderstanding, is not related to the discussion I was hoping to have.
Bgood:
Mutations and novel combinations of existing traits provide additions to variability.
Can you maybe explain "novel combinations of existing traits" a bit more? Is this the mechanism that over time adds traits?
I am saying if something prevents the organism from passing on their genes then it will not pass onto the next generation. This includes harmful genes.
This is not what I suggested. I stated that non-harmful genes will persist in the population. I used the two examples for contrast, see next quote.
Ok, so I want to distinguish here between traits and genes. Genes can be neutral or beneficial only, while only useful traits are preserved, according to Dawkins? Harmful genes will cause that specific branch to die out within a few generations, according to what I have read.
Multiple micro-evolution events.
Uh, ok. But micro-evolution is by definition changes within species, so at least by that definition you can have millions of these events and still not have speciation or new phyla. But if it is as you propose, then we are back to how that can be tested.
New phyla do not suddenly occur. They are defined as a phyla because they are so morphologically different.
Can you perhaps point to some evidence for the gradual development of phyla?
Not if by definition harmful mutations cause mortality or infertility.
Addressed above.
Very well, however in nature are there no pressures for living animals?
Sure, but how is that similar to you artificially selecting something that is selectively advantageous? Selection can only act on what is present, both in genetic and environmental terms, for the current generation. With you selecting, you have purposely decided that a trait would be beneficial, but natural selection is blind in that regard, it can only preserve what is present and therefore cannot select to breed bigfoot mice.
That brings another question to mind, at what point during an individuals lifespan does mutation take place? If mice with big feet were advantaged, did the first one with big feet just happen by chance, and its offspring spread the trait? Or was it born with small feet and then was subject to some environmental pressure that caused a mutation that gave it big feet that it passed on? The second option sounds a little Lamarckian to me, can any of you explain that to me a bit more?
No, selection only works for existing traits within a population.
So how do new traits come into existence?
Above you wrote:
Mutations and novel combinations of existing traits provide additions to variability.
If it can only select for existing traits, it will never select mutations and novel combinations?
May I ask given a large number of microevlution events why won't speciation not occur?
You may ask anything, of course
. I addressed this before, but in short, the definition of microevolution is changes within species, so multiple events cannot create new species. The observed changes in microevolution substitutes or decreases information, but does not add information so as to create new species, is the theory.
This can be speculated but given that the fossil record is majority hard material like bones we cannot know how an eye developed. However the variety of eyes within the natural world can give us clues. The inability to explain how specific things evolved only shows the limitations of our knowledge.
Since you are putting our lack of knowledge down to the limitations in understanding the specifics, you are arguing from ignorance, and the variety of eyes is mere speculation.
thereal wrote:
You are exactly right in assuming natural selection is a blind process in the sense that an organism is not changing to reach a certain "perfect form"; the changes are random in the sense that they are dictated by such things as environmental condition, sexual selection strategy, etc. This is a common misconception by many that animals are evolving "towards" something. The predictive value of natural selection does not lie in determining what the animal should look like in 1000 years given its present form, but how features of an animal should be expected to respond to a certain change in its environment. First comes change in environment, then the change in the organism.
Ok, that is how I understood the theory too.
This is not a circular argument as you insinuate, as the first meaning of "successful" and the second are not the same. This definition would be more clearly stated "the successful individuals (those that pass on the most genetic material to the next generation) are the ones that procreate best, while the ones that procreate best are the successful ones (those that possess characteristics that make them best suited to the current environment).
I'm not insinuating anything, I'm stating it. Your wordplay does not change the statement. What is the difference between those that pass on the most genetic material to the next generation and those that are best suited to the environment? Are they two different sets of organisms? That would defeat the theory of evolution, since by definition, those that are best suited to the environment has the best and most chance to pass on their genetic material.
Why can morphological characters not be used to this end, such as fur length, color, defenses. You do not need to introduce new mutations to test natural selection...existing characteristics can be examined for this purpose.
How does that test natural selection? You are merely observing physical traits, while speculating as to how those traits came to be. If you want to test natural selection, you cannot merely look at existing traits, you have to account for how they were selected at the point of development.
It would be great to examine the whole process from beginning to end (introduce mutation that is beneficial given the current environment, see those individuals with that mutation reproducing relatively more than those without, watch it spread in the population while other forms of that gene either remain static or decrease, etc.) This would show both natural selection and evolution (as evolution is simply a change in allele frequency over time). To see this in nature would be incredibly difficult and time consuming, as mutations occur randomly, you would need to be lucky to find the right population, response to environmental change lags behind the actual changes, etc.
So it has never been observed?
Although many of these separate components have been tested in the lab, for some reason I can't understand, this seems inadequate to those who don't believe these processes happen.
So we are to inductively believe that the whole complex process that you described above happens, based on the testing of seperate components. Since you were not specific as to which components they were, I cannot answer your question.
I have a real problem when people identify something as microevolution while not believing in macroevolution. These are one in the same, just different degrees of evolution.
They are the same, just different? Why do you not give us the definitions of both, so that we can see where they are the same?
It's like saying I believe in an embryo developing into the gastrula stage, then the gastrula eventually developing into a fetus, etc...but I don't believe that an embryo can develop into an adult. How can many microevolutionary events not lead to macroevolution? Maybe it's due to the impatience of humans that they want to see this process in their lifetime, but it's not going to happen....this process takes time.
Ok, how long does it take? How many generations, by order of magnitude, thousands, millions?