I fail to understand why the most religious person should be shaken by Darwin’s proposal. Darwin never said amn came from monkees, apes, etc. Darwin said the evidence suggests man shares a comon link to the primates, but he could never find his “missing link”. To this day, we have yet to find the missing link!
Hence, his theory leaves with just as many questions as the Creation itself.
That depends on what you mean by a missing link. If you mean an organism that is not human, that is ancestral to humans and that shares traits with both humans and the other great apes then we certainly have found the missing link. In fact we’ve found several of them.
Now if by ‘missing link’ you mean ‘missing strawman’ in the sense that it was never proposed to exist and somehow has to be a chimera of chimpanzee and human with chimp arms and a human brain and face then no, we haven’t found that. But nobody but creationists ever thought such a thing existed.
And while Darwin himself may not have said that humans descended fom apes pretty much every scientists after has said that. It is accepted scientific dogma today. All our most recent ancestors were apes just as we are ourselves.
The discovery of an entirely separate ecological system that had morphologically, and genetically identical species as the Earth would pretty much prove Intelligent Design. Since our current understanding of the process of evolution includes at least a minimum level of random mutation, it would make strong inroads into support for that theory as well.
The absence of such a discovery is not proof or disproof of anything.
“Stoning non conformists is part of science. Stoning conformists is also part of science. Only those theories that can stand up to a merciless barrage of stones deserve consideration. It is the Creationist habit of throwing marshmallows that we find annoying.” ~ Dr Popper ~
Even if true, which it isn’t, our relationship to other animals is the key part of evolution that creationists seem to have the most trouble dealing with. Simply in order to deny that humans are descended from other forms of life, they feel compelled also to deny not only the enormous body of evidence supporting evolution itself, but key findings of physics, chemistry, astronomy, and geology as well.
Not at all. It has provided excelllent answers to a great number of questions, which is why it is pretty much universally believed by scientists.
A bit of a hijack, but would it have been more gramatically correct for me to say “disproven” in the thread title, or did I get it right?
Hey, I like this one! It would be especially powerful if: (a) the environments in which the “identical species” were found differed dramatically from the environment in which they were found on Earth, and (b) the creatures didn’t seem especially well suited to those environments.
I’m presupposing we find a lot of such species (preferably, all those found on Earth): finding just one would lead me to believe, fairly strongly, that it was an introduced transplant - the “entirely separate ecological system” premise would seem weaker than the “natural selection is false” one.
Of course, this doesn’t answer the OP, since it’s not experimental. And it’s not a prediction of I.D. (that would give it the much-needed falsifiability), just a case in which we could be fairly sure it was correct.
Dictionary.com claims “disproved” is a word, and “disproven” isn’t. But “disproven” sounds better to me. Come join my revolution, as we overthrow the pedantic lexicons of old!
Well, it depends on whether you want to prove that Evolution never happens, or whether you want to prove that it’s not the only mechanism (aside from random events) for changes in populations over time.
As Timewinder said, you’d have to show that the postulates required for an evolutionary system don’t apply to life in the real world. [I’d slightly change his/her wording of 4) and 5) because there are other traits besides living longer that can give an advantage, but that’s a minor change].
Since we have seen these postulates do apply in many, many, cases, and have observed populations changing exactly as the theory predicts, you really can’t prove that Evolution never happens.
How could you prove that there is another mechanism at work? I suppose showing changes in a population over time that were too large to be random, yet unrelated to the environment. Though, given the weight of other examples, the most likely explanation would still be that the changed were caused by selection in the environment, just in a way that we hadn’t noticed yet.
Actually evolution does not require that heritable traits be genetic. It’s just that genes happen to be how traits are inherited. See TimeWinder’s six-point summary.
Evolution, in its most basic sense, is just a change of gene frequences in populations. Some evolution happens not through natural selection, but through random processes. When populations are very small, some genetic alleles can become extinct in a population simply by chance, not because they are selected against. Likewise '“silent” mutations, that is, the change of a base pair in a gene that does not affect its expression, are generally thought not to be subject to selection, and thus accumulate in the genome over time. Both these examples represent evolution in its broadest sense.
The fact that evolution has occurred in the past, in the sense that organisms have changed through time, is a hypothesis that could easily be falsified in many many ways which have already been discussed here, if in fact it were false. However, even some evolutionists have contended that the process of evolution by natural selection is not falsifiable, because it is a tautology. How can you determine if “survival of the fittest” is at work, if you define fitness in terms of who survives?
I don’t want to get into a discussion of this particular issue here, except to point out that questions about the exact process by which evolution has taken place, whether Darwinian (natural selection) or something else (e.g. Lamarkian evolution), don’t call into question the fact that evolution has taken place in the past.
Evolution in the scientific sense is simply change over time. In the most basic form, it is specifically the change in alleles within a population over time. And really, none of those six postulates are necessary for such to occur. Mere random mutation is sufficient to produce evolution.
What Darwin demonstrated is that the bulk of evolutionary change that has occurred is the result of the mechanism he termed natural selection. And for that to occur, it is necessary to have some basic premises:
As a result, the general trend of the population will be such that each subsequent generation is better at obtaining those resources; the population “adapts”.
Natural selection can be falsified, as I argued in the thread linked to by Contrapuntal, by demonstrating that changes in the environment (which, in turn, determines which trait variations prove “favorable” at any given time) produce no measurable trend in allele frequencies over time. If changes in allele frequencies within a population are more or less random, regardless of the environmental conditions, then natural selection is not at work.
To demonstrate that evolution itself does not occur, you would have to demonstrate that mutations do not occur. But that just brings us back to Special Creation as the only alternative, which is unfalsifiable.
If I may nitpick Darwin’s Finch, I do not think that
is a necessary condition for evolution. (I’d also point out again that changes in gene/allele frequencies is not evolution, per se, but a direct consequence of evolution. Instead, evolution is the change in heritable traits.)
For example, assume there is no limit to population size. Let’s say we start 10 red and 10 blue widgets. They are identical, except red widgets produce 2 offspring every generation, and blue ones produce 3. The first generation has 20 widgets, 50% blue. The tenth generation has over 200,000 widgets and is 97% blue. That’s evolution.
The evolution found in the real world will, of course, almost always be of the kind with limited resources. But I’m sure there’s restricted circumstances where resources are effectively unlimited. (The first generations of bacteria in petri dish or cane toads in Australia.)
I said that limited resources and competition were prerequisites for natural selection, not for evolution in general. Natural selection cannot function without competition as NS depends on certain variations being “more favorable” than others. In the absence of competition (as can sometimes occur when resources are very plentiful relative to the population size), NS tends to take a back seat to more stochastic modes of changes.
You can’t have “change in heritable traits” without “changes in gene/allele frequencies”. Nor can you have “changes in gene/allele frequencies” without “change in heritable traits”. At the population level, the two are inextricably linked, and both describe the same process - evolution - at different levels of examination. Neither is a “consequence” of evolution, but the mere fact that they do change is what evolution is.
Well no, competition for resources is not necessary for natural selection to take place. Certain traits, such as the ability to withstand bad weather, can confer increased fitness, even if individuals do not compete for resources at all. Some organisms may be kept so rare by predation or environmental conditions that individuals never compete for resources, but they can evolve through natural selection all the same.
There are also quite a few creationists that claim not only does speciation occur, but occurs much faster than evolutionists suppose. This is necessary in order to fit all the animals in the ark. And that “the creation model depends heavily on speciation.” I just love the way the speak of the creation model, as though there is only one creation model.
That is only true for organisms whose heritable traits are controlled by genes. True, the heritable traits of all known organisms is controlled by genes, but that does not mean we do not expect evolution to hold for any other organisms we discover. Heritability is essential, genes are not.
Yes, and my red-blue widget example demonstrates natural selection without resource limitations.
Recall that Darwin’s orginal formulation of natural selection had, as a basic premise, the idea that all organisms produce more offspring than can possibly survive. This is true even for slowly-breeding organisms, such as elephants. Further, there is a fundamental drive to reproduce; thus, populations will, if left unchecked, grow. Eventually, then, there comes a point where individuals within a species must compete to survive. In theory.
For some very rare species, as you suggest, it may well be that, for them, resources are effectively infinite as there aren’t enough individuals present to make a significant impact on whatever resources they might use. In such cases, however, unless population growth was nonexistent, there is still a form of competition for survival against predation. Sibling offspring, for example, may possess variations in traits that allow one sibling to escape predation while the other falls to predation. That may well be stretching the definition of “competition”, however. But still, even rare species must have sufficient variation present for differential survivability atrributable to those variations to have an effect on the genetic makeup of the overall population in order to demonstrate natural selection. If the populations of those rare species are declining, then I think it could often be argued that their pending extinction is not necessaily attributable to natural selection (but see below).
As for raw environmental effects (such as a shift in temperature drastic enough to kill off a certain percentage of individuals outright, or a bout of sudden, severe weather), I would submit that the survivors of many such shifts are simply the result of luck of the draw, rather than natural selection. I am reminded here of Raup’s “field of bullets” scenario for extinction, as opposed to the “fair game” scenario, wherein the extinction is the result of simply being outdone by a competing species. The survivors of such catastrophic events need not adapt to the new conditions, as they already had to possess the correct set of traits that allowed them to survive in the new environment in the first place. Their subsequent offspring, then, will also likely already possess the necessary “baseline” survival traits (assuming those traits were heritable, etc.).
When such organisms are discovered, undoubtedly the definition of evolution will be revised. Until then, it is what it is. For example,
Bolding mine. I think you are splitting theoretical hairs that may not even exist.
Not really. You described two subpopulations, each with different breeding rates. That’s simple mathematical population growth; nothing is being “selected” at all, either for or against. Evolution, sure; natural selection, nope. If it were shown that in a given population widgets could be born blue or red (regardless of parental color), and that any pairing involving blue widgets tends to produce more offspring, then it could proabbly be demonstrated that blue widgets will tend to be selected for. But if blue widgets only ever pair with blue widgets and red only with red, then you’ve got nothin’.
Come to think of it, if the only trait in question is color, then you don’t even have evolution. The relative frequency of “blue” within the blue population will always be 100% (similar for the red), thus no evolution is occurring in your example as given. It’s just straight population growth.
It’s the theoretical physicist in me. I agree that for practical work biologists assume heritability and genes always coincide. My point is that it is wise to remember evolution is not so fragile that the discover of non-genetic heritability would falsify it. I think you would agree with that.
As for my numerical example of natural selection with unlimited resources, I can make a more sophisticated model, if you like (after I return from my belated holiday weekend). But I thought it would be obvious that it’s the change of relative frequency that’s important for evolution, not absolute numbers. And so an ever-expanding population will experience evolution just the same as a fixed-size population.
What I am disputing is not that competition for resources is usually an important factor in natural selection, or a key part of Darwin’s original argument. I am just disagreeing with your statement that competition is necessary for natural selection to take place. It very clearly is not a necessary condition.
If some individuals survive a period of severe winter weather because of some heritable trait, such as thicker fur, that is natural selection at work, even though there is no competition for resources involved. (Of course there could be competition, if individuals are competing for shelter, but if it is a sparse population and shelter is not a limiting resource it doesn’t have to be.) In fact, one of the very first demonstrations of natural selection at work was based on a study of mortality of small birds (I think it was House Sparrows) during a severe winter storm.
If individuals survive catastrophic events, and if their survival has been due to some heritable trait and not pure chance, then the population has adapted to the altered conditions through natural selection. (And such adaptation is a population characteristic, not an individual one.)
DF, I’m surprised that you are disputing this point, since I know you are quite knowledgeable on these topics. But the contention that competition for resources is a prerequisite for natural selection is simply incorrect.