What is the "engine" of evolution?
AUTHOR: Allen MacNeill
SOURCE: Original essay
COMMENTARY: That's up to you...
Ever since Darwin, the primary "engine" of evolution has been considered to be natural selection. However, if one takes a closer look at this, it is clear that natural selection is not an "engine," it is an outcome. If evolution is defined as change in the characteristics of the members of a population over time and natural selection is defined as unequal non-random survival and reproduction (or, more parsimoniously, differential reproductive success), then the underlying cause of the changes that are differentially preserved over time is the real "engine" of evolution by natural selection.
And what might this "engine" of change be? Exactly what Darwin said it was in the Origin of Species: the "laws of variation" of which naturalists of his time were almost "completely ignorant." That is, given that some variations are heritable and that they can be passed from parents to offspring in the process of reproduction, then it is the processes that cause such variations that are the real "engine(s)" of evolution, including evolution by natural selection.
Darwin was on the right track when later on he sought out the specifics of the "engines of variation" in Variation of Animals and Plants Under Domestication, published in 1868. Darwin suggested that the rate of variation changed over time, in response to specific changes in the environment. For example, he pointed out that the variation between domesticated animals and plants was considerably greater than that found in the wild. This suggested to him that something about domestication – increased food, improved nutrition, lack of predators, etc. – caused an increase in the production of variations that were then exploited by animal and plant breeders.
However, it is now generally accepted that the only real difference between domesticated and wild animals and plants, in terms of variation, is that the conditions of domestication allow more variants to survive and reproduce, rather than causing more of them to be produced in the first place. I do not know enough genetics to say whether or not this is the case, but it seems to me at least that Darwin's idea is worth empirical investigation. Here are the relevant questions (which may or may not already have answers):
• Is the rate of generation of genetic and phenotypic variation a constant?
If the answer to this question is "yes," then all we need to investigate is the actual genetic and developmental mechanisms by which such variations are generated. However, if the answer is "no," then the rate of generation of genetic and phenotypic variations is variable, which immediately suggests more questions:
• Is the increased rate of generation of variations correlated with any identifiable factor in either the genetics/development or the environment of organisms in which such variable rates of variation are observed?
If the answer to this question is "no," then we may safely assume that the underlying "engine(s)" of variation is/are entirely random, insofar as we can observe it changing randomly over time. However, if the answer is "yes," then there are more questions:
• Via what mechanism(s) is the increased rate of variation generated, and are the "triggers" for such increased variation endogenous, exogenous, or some combination of the two?
Clearly, the "engine(s)" of variation are prodigious, as it/they have been able over time to modify something as simple as a mycoplasm into an oak tree or a blue whale. Some supporters of "intelligent design" (ID) would dispute this statement, of course, claiming (without any empirical evidence) that "you can't get here from there." However, we clearly have gotten here from there; the real question is "how?" There are logically at least two possibilities:
• The process(es) by which the "engine(s) of variation" have produced the necessary variation have operated endogenously by means of a prodigious (and undirected) "random variation generator," the products of which have been sorted over time by natural selection (i.e. the Darwinian hypothesis), or
• The process(es) by which the "engine(s) of variation" have produced the necessary variation have operated endogenously by means of a less prodigious "non-random variation generator," the products of which have been sorted over time by natural selection (i.e. the ID hypothesis).
Noticing that the only difference between these two possibilities is the amount of variation and its source immediately suggests a way of testing the two hypotheses: do the currently identified mechanisms of genetic and phenotypic variation produce enough variation to get from there to here, or not? If the answer is "yes," then the ID hypothesis is unnecessary, and therefore irrelevent to science.
So, the next obvious question is, what are the currently identified mechanisms of genetic and phenotypic variation, and do they provide enough variation to get here from there? The answer to this question will be posted soon -watch this space.
And as always, comments, criticisms, and suggestions are warmly welcomed!
--Allen
Labels: evolution, genetic variation, intelligent design, phenotypic variation
posted by Allen MacNeill @ 6/14/2007 09:46:00 AM
7 comments
7 Comments:
However, it is now generally accepted that the only real difference between domesticated and wild animals and plants, in terms of variation, is that the conditions of domestication allow more variants to survive and reproduce, rather than causing more of them to be produced in the first place.
Well, up to a point. Increased output is something that can and is regularly selected for in plant breeding, especially for larger corn stalks with more ears, more grains of wheat per blade, etc.
Of course today, we've used genetic engineering to perfect that "productivity" even more. All good and well except for the insane amount of fertilizer it requires to keep these plants happy (at an expense that makes it difficult for the 3rd world to use).
Dr. MacNeill,
I think you've identified the real issue for debate. However, I think there are more participants than Neo-Darwinists and IDists. We should also include Margulis's Symbiogenesis; Kaufman's Self-Organization theory; and James Shapiro's theory, the name of which I can't remember.
And then, I think Mike Gene might argue that the Designer could have "programmed" the orinal cells to randomly generate variation in a certain direction. Where do we put him?
Hi, Allen. I think you've pinpointed the point of contention. I even think you've asked the right questions.
How long ago was it when Gould came up with punctuated equilibrium to explain what we see in the fossil record? Since then we've identified mechanisms that do increase mutation rates. These look to be endogenous, but trigger-responsive to selective pressure. A combination of the two. I expect there will be others as well. And that they'll be constrained to certain sections of the genome, thus less than random there too.
Not that exogenous and endogenous accidents don't happen. They do. So there's some randomness to the overall equation, I just don't think those mutations are the ones that count much for evolutionary purposes.
The staunch NDS'ers want us to believe life is just hapless clay which Nature (big-n) shapes to its non-random specifications (or randomly kills anyway). The Creationists want us to believe life is hapless clay shaped from beyond the universe by God's whims. The question of who and what we are is a natural battleground for science and religion. But out here in reality most of us think you all take your metaphysics way too seriously.
We live and die here in the material world, so material descriptions will serve us fine, FAPP - For All Practical Purposes. But if we're fed garbage for ideological reasons - either way - we're not likely to be very amused. And now I hear that even Professor MacNeill is asking loaded questions about the "engine" of evolution! What will happen next?
The answer is out there. Or maybe in here...
Nobody gets any useful knowledge from "random" anything. That's a human limitation-built brick wall around causation, not a believable explanation of life and evolution. "Look harder," as Rafiki would say.
"Is the rate of generation of genetic and phenotypic variation a constant?"
I recall reading that you can get bacteria to take-up DNA by starving it and then shocking it. So, as far as the rate of horizontal gene transfer, there seem to be external factors at play.
According to this paper, we can expect to see mutation rates vary:
http://www.blackwell-synergy.com/doi/pdf/10.1111/j.1365-2958.2006.05150.x?cookieSet=1
"If the answer is "yes," then the ID hypothesis is unnecessary"
I assume you mean "unnecessary to explain variations". One of the arguments IDists have put forward is based on "Haldane's Dilemma" - saying that only a certain number of mutations can reach fixation within a specific amount of time, and that number is too low to explain human differences from an ape-like common ancestor. I wrote a paper a few months ago (and submitted it to TalkOrigins, though the site seems to be frozen) that shows why this "maximum fixation rate" is not at all a maximum rate at all.
Evolution is in the mind of the believer. It goes no farther than that.
If evolutionists want to end the arguments all they have to do is, get their brilliant heads together and assemble a 'simple' living cell. This should be possible, since they certainly have a very great amount of knowledge about what is inside the 'simple' cell.
After all, shouldn't all the combined Intelligence of all the worlds scientist be able the do what chance encounters with random chemicals, without a set of instructions, accomplished about 4 billion years ago,according to the evolutionists, having no intelligence at all available to help them along in their quest to become a living entity. Surely then the evolutionists scientists today should be able to make us a 'simple' cell.
If it weren't so pitiful it would be humorous, that intelligent people have swallowed the evolution mythology.
Beyond doubt, the main reason people believe in evolution is that sources they admire, say it is so. It would pay for these people to do a thorough examination of all the evidence CONTRARY to evolution that is readily available: Try answersingenesis.org. The evolutionists should honestly examine the SUPPOSED evidence 'FOR' evolution for THEMSELVES.
Build us a cell, from scratch, with the required raw material, that is with NO cell material, just the 'raw' stuff, and the argument is over. But if the scientists are unsuccessful, perhaps they should try Mother Earth's recipe, you know, the one they claim worked the first time about 4 billion years ago, so they say. All they need to do is to gather all the chemicals that we know are essential for life, pour them into a large clay pot and stir vigorously for a few billion years, and Walla, LIFE!
Oh, you don't believe the 'original' Mother Earth recipe will work? You are NOT alone, Neither do I, and MILLIONS of others!
Evolution is in the mind of the believer. It goes no farther than that.
The idea that evolution doesn't work is based on wishful thinking, ignorance, and creationist propaganda.
After all, shouldn't all the combined Intelligence of all the worlds scientist be able the do what chance encounters with random chemicals, without a set of instructions, accomplished about 4 billion years ago,according to the evolutionists, having no intelligence at all available to help them along in their quest to become a living entity.
The blind universe has a universe-size laboratory to try different combinations. Scientists have to get all the factors right at the same time in a tiny little space. This is akin to saying, "Joe Schmoe won the lottery, and if you scientists are really so smart, why don't you buy a couple lottery tickets and win, too. If you don't win, it proves that the lottery is fixed by someone."
Try answersingenesis.org. The evolutionists should honestly examine the SUPPOSED evidence 'FOR' evolution for THEMSELVES.
As a former YEC and someone familiar with Answeringenesis, I can tell you that creationist ideas are ridiculous, and I saw them for what they were. On numerous occasions, I've seen Answersingenesis make blatantly false statements, get their data wrong, and generally display their deep ignorance - something that is obvious to people with a little bit of knowledge on the subjects they talk about. All creationists and AIG have is marketing, rhetorical games, misinformation that plays on people's preexisting ignorance, a population of people eager to eat-up their garbage.
Build us a cell, from scratch, with the required raw material, that is with NO cell material, just the 'raw' stuff, and the argument is over.
We all know that's a red herring. The minute scientists created a cell, you creationists would declare that it was "intelligently designed" and therefore, proves nothing.
Bilbo wrote: And then, I think Mike Gene might argue that the Designer could have "programmed" the orinal cells to randomly generate variation in a certain direction. Where do we put him?
Front loading is a meaningless concept as it is indistinguishable from natural initial conditions. Of course we can always propose some mythical entity that did something, somehow, somewhere but surely we should not confuse such a concept with a scientifically fruitful approach?
Post a Comment
<< Home