320 Years of History
Gold Member
This thread is inspired by several others here. I initially composed the remarks below to include in "page God knows what" of one of them. Then I decided this is too much work to have it buried in the abyss of some thread. This post turned into something I had no intention of writing when I first began it. Quite literally, it evolved (pun intended) into what it is. It is, in its own way, an tiny example of evolution. <winks>
(Note: I've assumed you meant "cannot call a scientific theory proven" rather than calling it a proof, and I've assumed you understand that the theory itself is the (or several) assertion(s) that is then supported with a proof, be it one that is inductively or deductively arrived at.)
No, one cannot, at least not in the exact same way one can say that of a theory supported by deductive proof rather than inductive proof. As with any inductive argument, 100% assuredness isn't possible.
Scientific Theories and Falsifiability
The inductive nature of scientific theories, and in particular that of evolution, should be construed by noone as suggesting, much less affirming, that a competing inductively developed theory (assertion(s) + proof + conclusion(s)) is its peer or better in terms of the probability of its verity. To do is to ignore the principle of falsifiability. (Also see Conjectures and Refutations, by Karl Popper, a relevant chapter of which is found here.) The falsifiability of evolution is an important part of establishing evolution as a scientific theory on the principles of falsifiability. Creationists and others sometimes claim that evolution and common descent cannot be falsified and consequently are not science. In other cases, intelligent design advocates insist that there is no way to falsify evolution because any new evidence just becomes "evolution in action" anyway.
This, however, is simply not the case as there are numerous pieces of evidence that could falsify evolution. The assertions made by Creationists may be due to a misunderstanding between the concept of "falsifiability" and "has been falsified". More intelligent [see Note 1 below] criticisms of the falsifiability of evolution focus on how new evidence (such as new fossil or climatology data) always leads to evolution and never towards design, even when theories about specifics of a species' development are changed significantly in light of evidence. However, this is a case of the science having been wrong before gambit, and has little to do with falsifiability itself.
A scientific theory is a series of statements about the causal elements for observed phenomena. A critical component of a scientific theory is that it provides explanations and predictions that can be tested. Scientific theories cannot be proved outright – they can only fail to be disproved, and this means pointing out what evidence could disprove the theory. If a scientific theory is not falsifiable at the start, such as with Russell's Teapot, it makes no difference whether it is true.
Evolution is Not "Just a Theory"
Creationist and Intelligent Design proponents often like to describe the theory of evolution as "just a theory." This relies on equivocating the common usage of the term theory (meaning "idea" or "guess" - more literally speaking, "hypothesis") with the scientific meaning. Theories are the single highest level of scientific achievement and nothing is "just a theory" -- that would be like saying Bill Gates is just a multibillionaire. Additionally, one might say that the notion of evolution is "just a theory" in the same way that Cell Theory and the Theory of Gravitation (fundamental principles of biology and physics, respectively) are "just theories."
Another common misconception is that a theory is the step one goes through on the way to articulating/uncovering a law of science. Scientific laws and theories are two very different things and, despite what it may seem, one never becomes the other.
Scientific laws are factual observations usually derived from mathematical modeling; they merely distill empirical results into concise verbal or mathematical statements that express a fundamental principle of science - for example, gravity attracts, force equals mass times acceleration and so on. Theories are the causal explanations behind what creates these laws and observations of nature. Theories also combine laws into a framework that is greater than the sum of its parts. In genetics, many different laws describe how genes interact in different combinations to influence heredity - work done principally by Gregor Mendel. Genetic theory combines these laws into a unified framework that can be used as an explanation and to make predictions. Evolutionary theory then combines genetic theory, the theory of natural selection and other theories with the various laws with which they are associated into a complex framework that forms the basis of much research in the field of biology.
Even superb theories, or laws, can be superseded by more successful theories. For instance, Newton's "Law" of gravitation is superb at predicting the path of a spacecraft among the outer planets of the solar system, but it breaks down when large masses are involved, such as that of the Sun. The precession of the aphelion of Mercury can only be explained by Einstein's general relativity, which is a refinement of Newton's Law taking into account the slight bending of spacetime near the Sun.
Because of the ability for good theories to make predictions, even if they are shown to be false (or more specifically, inaccurate in certain conditions) they can still be used to make predictions that are useful approximations. Newtonian mechanics may well be total nonsense in the light of 20th Century physics pioneered by Einstein, but no one uses Special Relativity to work out the momentum of an automobile. And while quantum mechanics may, in principle, be completely replaced by something else, nothing is going to change the fact that the Schrodinger Equation predicts the spectroscopic features of the hydrogen atom perfectly. Moreover, some "silly" theories of old may have some use because of how they work, the classic example being that of a flat Earth. While everyone knows that the Earth isn't flat, someone building a shed in their garden doesn't need to allow for the curvature of the Earth.
One common misconception is that scientific theories are derived from hypotheses that have met with confirming experimental evidence - and that there is a hierarchy of science starting with the hypothesis that reaches theory and eventually reaches law. This is in fact wrong, as theories are completely separate from hypotheses - a hypothesis does not become a theory, and if experimental evidence contradicts a theory it is not downgraded to a hypothesis.
A theory is a fully working model, supported by evidence and accepted as valid and accurate at predicting and testing observations. A hypothesis tends to be a bit smaller, a guess or conjecture about how something might work - a "working hypothesis" is something with good enough supporting evidence that an individual will accept as true for the sake of furthering their research. Importantly, a hypothesis is a testable statement and unlike a theory it might well be proved to be "right" or "wrong" without causing any major problems for established science. It is a hypothesis that leads to experiment and it is many of these factors - ideas, concepts, experiments, evidence and so on - working together that theories emerge from.
What might falsify the theory of Evolution?
Disproving evolution first requires one look at what the theory predicts to determine where it can be shown to make incorrect predictions. It is easy to become side-tracked by specifics of the theory, such as individual evolutionary pathways of certain features, and confuse these with what would falsify the overall theory of evolution by natural selection. Indeed, many Creationists do this whenever a new discovery is made in biology that causes scientists to rethink some pieces of evolution. To avoid this problem, it is best to be clear what evolution is.
Evolution is based on three main principles: variation, heritability and selection. Given these three principles, evolution must occur, and many features of evolution appear given only these three guiding principles. If any of these were shown to be flawed then the theory would be untenable.
Consequently any of the following would destroy the theory:
Falsifiable Predictions of Evolution
Given the preceding, it stands to reason that the theory of evolution must repeatedly lead to testable predictions being made and either confirmed or refuted. (One of those predictions is discussed in the videos below.) There are oodles of such predictions, and so far, not one of them has failed to materialize as predicted by the theory of evolution. Some examples are here [see Note 3 below]:
What Might Falsify Common Descent?
Common descent is the scientific theory that all living organisms on Earth descended from a common ancestor. Biologists have evidence that all life developed from a common ancestor that lived just under 4 billion years ago, and the concept is accepted by virtually all scientists working in the field. The structures and functions of all living organisms are encoded in the same basic nucleic molecules, DNA and RNA. Similarities in amino acid sequences between various organisms also suggest common descent, and the fossil record also shows cases in which one plant or animal type evolved into different types over time. The details of this process are shown in clade diagrams. [http://www.gwu.edu/~clade/faculty/lipscomb/Cladistics.pdf]
Creationists reject common descent as it implies an evolutionary model. Young Earth creationists, as Biblical literalists, reject it outright, believing that life was created within a few days less than ten thousand years ago. Intelligent design proponents may accept some aspects of common descent, as long as they are allowed to claim that the "designer" interfered with the genes and mutations along the way, then deferring what's not explained to "we don't know" what happened.
What Evidence Supports Common Descent?
There's a lot of it. I'm going to stick to the approach of the rest of this post and provide only a very high level overview. The most powerful evidence supporting common descent is:
Understanding the Creationists' Arguments Against Common Evolutions' Predictive Capability
Some creationists have claimed that true science must make predictions, but evolution only describes what happened in the past, so it is not predictive. However, this argument has several flaws:
Notes:
(Note: I've assumed you meant "cannot call a scientific theory proven" rather than calling it a proof, and I've assumed you understand that the theory itself is the (or several) assertion(s) that is then supported with a proof, be it one that is inductively or deductively arrived at.)
No, one cannot, at least not in the exact same way one can say that of a theory supported by deductive proof rather than inductive proof. As with any inductive argument, 100% assuredness isn't possible.
Scientific Theories and Falsifiability
The inductive nature of scientific theories, and in particular that of evolution, should be construed by noone as suggesting, much less affirming, that a competing inductively developed theory (assertion(s) + proof + conclusion(s)) is its peer or better in terms of the probability of its verity. To do is to ignore the principle of falsifiability. (Also see Conjectures and Refutations, by Karl Popper, a relevant chapter of which is found here.) The falsifiability of evolution is an important part of establishing evolution as a scientific theory on the principles of falsifiability. Creationists and others sometimes claim that evolution and common descent cannot be falsified and consequently are not science. In other cases, intelligent design advocates insist that there is no way to falsify evolution because any new evidence just becomes "evolution in action" anyway.
This, however, is simply not the case as there are numerous pieces of evidence that could falsify evolution. The assertions made by Creationists may be due to a misunderstanding between the concept of "falsifiability" and "has been falsified". More intelligent [see Note 1 below] criticisms of the falsifiability of evolution focus on how new evidence (such as new fossil or climatology data) always leads to evolution and never towards design, even when theories about specifics of a species' development are changed significantly in light of evidence. However, this is a case of the science having been wrong before gambit, and has little to do with falsifiability itself.
A scientific theory is a series of statements about the causal elements for observed phenomena. A critical component of a scientific theory is that it provides explanations and predictions that can be tested. Scientific theories cannot be proved outright – they can only fail to be disproved, and this means pointing out what evidence could disprove the theory. If a scientific theory is not falsifiable at the start, such as with Russell's Teapot, it makes no difference whether it is true.
Evolution is Not "Just a Theory"
Creationist and Intelligent Design proponents often like to describe the theory of evolution as "just a theory." This relies on equivocating the common usage of the term theory (meaning "idea" or "guess" - more literally speaking, "hypothesis") with the scientific meaning. Theories are the single highest level of scientific achievement and nothing is "just a theory" -- that would be like saying Bill Gates is just a multibillionaire. Additionally, one might say that the notion of evolution is "just a theory" in the same way that Cell Theory and the Theory of Gravitation (fundamental principles of biology and physics, respectively) are "just theories."
Another common misconception is that a theory is the step one goes through on the way to articulating/uncovering a law of science. Scientific laws and theories are two very different things and, despite what it may seem, one never becomes the other.
Scientific laws are factual observations usually derived from mathematical modeling; they merely distill empirical results into concise verbal or mathematical statements that express a fundamental principle of science - for example, gravity attracts, force equals mass times acceleration and so on. Theories are the causal explanations behind what creates these laws and observations of nature. Theories also combine laws into a framework that is greater than the sum of its parts. In genetics, many different laws describe how genes interact in different combinations to influence heredity - work done principally by Gregor Mendel. Genetic theory combines these laws into a unified framework that can be used as an explanation and to make predictions. Evolutionary theory then combines genetic theory, the theory of natural selection and other theories with the various laws with which they are associated into a complex framework that forms the basis of much research in the field of biology.
Even superb theories, or laws, can be superseded by more successful theories. For instance, Newton's "Law" of gravitation is superb at predicting the path of a spacecraft among the outer planets of the solar system, but it breaks down when large masses are involved, such as that of the Sun. The precession of the aphelion of Mercury can only be explained by Einstein's general relativity, which is a refinement of Newton's Law taking into account the slight bending of spacetime near the Sun.
Because of the ability for good theories to make predictions, even if they are shown to be false (or more specifically, inaccurate in certain conditions) they can still be used to make predictions that are useful approximations. Newtonian mechanics may well be total nonsense in the light of 20th Century physics pioneered by Einstein, but no one uses Special Relativity to work out the momentum of an automobile. And while quantum mechanics may, in principle, be completely replaced by something else, nothing is going to change the fact that the Schrodinger Equation predicts the spectroscopic features of the hydrogen atom perfectly. Moreover, some "silly" theories of old may have some use because of how they work, the classic example being that of a flat Earth. While everyone knows that the Earth isn't flat, someone building a shed in their garden doesn't need to allow for the curvature of the Earth.
One common misconception is that scientific theories are derived from hypotheses that have met with confirming experimental evidence - and that there is a hierarchy of science starting with the hypothesis that reaches theory and eventually reaches law. This is in fact wrong, as theories are completely separate from hypotheses - a hypothesis does not become a theory, and if experimental evidence contradicts a theory it is not downgraded to a hypothesis.
A theory is a fully working model, supported by evidence and accepted as valid and accurate at predicting and testing observations. A hypothesis tends to be a bit smaller, a guess or conjecture about how something might work - a "working hypothesis" is something with good enough supporting evidence that an individual will accept as true for the sake of furthering their research. Importantly, a hypothesis is a testable statement and unlike a theory it might well be proved to be "right" or "wrong" without causing any major problems for established science. It is a hypothesis that leads to experiment and it is many of these factors - ideas, concepts, experiments, evidence and so on - working together that theories emerge from.
What might falsify the theory of Evolution?
Disproving evolution first requires one look at what the theory predicts to determine where it can be shown to make incorrect predictions. It is easy to become side-tracked by specifics of the theory, such as individual evolutionary pathways of certain features, and confuse these with what would falsify the overall theory of evolution by natural selection. Indeed, many Creationists do this whenever a new discovery is made in biology that causes scientists to rethink some pieces of evolution. To avoid this problem, it is best to be clear what evolution is.
Evolution is based on three main principles: variation, heritability and selection. Given these three principles, evolution must occur, and many features of evolution appear given only these three guiding principles. If any of these were shown to be flawed then the theory would be untenable.
Consequently any of the following would destroy the theory:
- Showing that organisms with identical DNA have different genetic traits.
- Showing that mutations do not occur.
- Showing that when mutations do occur, they are not passed down through the generations.
- Showing that although mutations are passed down, no mutation could produce the sort of phenotypic changes that drive natural selection.
- Showing that selection or environmental pressures do not favor the reproductive success of better adapted individuals.
- Showing that even though selection or environmental pressures favor the reproductive success of better adapted individuals, "better adapted individuals" (at any one time) are not shown to change into other species.
Falsifiable Predictions of Evolution
Given the preceding, it stands to reason that the theory of evolution must repeatedly lead to testable predictions being made and either confirmed or refuted. (One of those predictions is discussed in the videos below.) There are oodles of such predictions, and so far, not one of them has failed to materialize as predicted by the theory of evolution. Some examples are here [see Note 3 below]:
- The Predictive Power of Evolutionary Biology and the Discovery of Eusociality in the Naked Mole Rat
- You won't need the audio for this video. Apologies for the "anti-creationist" approach inherent in this video.
What Might Falsify Common Descent?
Common descent is the scientific theory that all living organisms on Earth descended from a common ancestor. Biologists have evidence that all life developed from a common ancestor that lived just under 4 billion years ago, and the concept is accepted by virtually all scientists working in the field. The structures and functions of all living organisms are encoded in the same basic nucleic molecules, DNA and RNA. Similarities in amino acid sequences between various organisms also suggest common descent, and the fossil record also shows cases in which one plant or animal type evolved into different types over time. The details of this process are shown in clade diagrams. [http://www.gwu.edu/~clade/faculty/lipscomb/Cladistics.pdf]
Creationists reject common descent as it implies an evolutionary model. Young Earth creationists, as Biblical literalists, reject it outright, believing that life was created within a few days less than ten thousand years ago. Intelligent design proponents may accept some aspects of common descent, as long as they are allowed to claim that the "designer" interfered with the genes and mutations along the way, then deferring what's not explained to "we don't know" what happened.
What Evidence Supports Common Descent?
There's a lot of it. I'm going to stick to the approach of the rest of this post and provide only a very high level overview. The most powerful evidence supporting common descent is:
- Anatomical homologies -- Throughout the domains of life, organisms show a distinct pattern of constraints based on homology in development and construction of the body. For example, tetrapods have five digits because the ancestor of tetrapods had five digits. When a tetrapod does not seem to have five obvious digits, a review of their development shows that they start development with five and that they fuse together later to form fewer numbers. Although fossils are usually not direct evidence in favour of common descent, a purely anatomical resemblance to living species is a form of strong supportive evidence. Some more recent fossils contain traces of tissue or DNA that can be used to determine in what way the fossil is related to living species.
- Transitional Forms
Creationists assert that transitional forms have not been found. Little is farther from the truth.
- Fins to Limbs: New Fossil Gives Evolution Insight
- Evolution: Library: Transitional Tetrapod Fossil
- http://archaeologyinfo.com/human-evolution-timeline/
- Transitional forms
Of course, one "move the goalposts" and keep asking for more transitional forms between other transitional forms. Such demands tacitly assume that the progression from freshly dead body to fossil is a common occurrence; however, fossilization, to say nothing of finding them, is the exception to the rule (usually, cadavers decay completely) and seismic, volcanic, tectonic and human activity have destroyed or buried many fossils.
Furthermore and in my opinion, "transitional forms" is a bit of a misnomer. A case can be made for all or no lifeforms being transitional ones. All creatures and plants today seem to be very well adapted to their environment, and none looks obviously "transitional". The same would have been valid in the past; only with the benefit of hindsight can they be labeled "transitional." The only forms that are not obviously "transitional" are those with no living descendants or those that have survived to this day without change. To put it another way, evolution does not occur in between periods in which no changes occur; though it may be slow with occasional bursts in speed, mutation and natural selection are ongoing processes. [Someone at some point in the recent evolution/creation discussions asked something pertaining to or that explains extinct species....I'm not sure of the exact wording of the inquiry, and I ain't looking for it right now...The preceding sentence comprises part of the answer, at least if my recollection is accurate re: what was asked.]
Furthermore and in my opinion, "transitional forms" is a bit of a misnomer. A case can be made for all or no lifeforms being transitional ones. All creatures and plants today seem to be very well adapted to their environment, and none looks obviously "transitional". The same would have been valid in the past; only with the benefit of hindsight can they be labeled "transitional." The only forms that are not obviously "transitional" are those with no living descendants or those that have survived to this day without change. To put it another way, evolution does not occur in between periods in which no changes occur; though it may be slow with occasional bursts in speed, mutation and natural selection are ongoing processes. [Someone at some point in the recent evolution/creation discussions asked something pertaining to or that explains extinct species....I'm not sure of the exact wording of the inquiry, and I ain't looking for it right now...The preceding sentence comprises part of the answer, at least if my recollection is accurate re: what was asked.]
- DNA and RNA code -- Almost all organisms use the same three-letter code for translating RNA into proteins. There are variations, such as the code used by mitochondria and some bacteria and fungi, but the differences are only minor. Regardless of the slight differences, all organisms use the same coding mechanism for translating the code into amino acid sequences.
- Endogenous retroviral insertions -- Ancient retroviruses inserted inactivated viral genes into genomes. For a retrovirus to be inherited in all members of a species, a series of highly improbable events must occur. The virus must insert into a gamete cell and it must mutate so it is inactive. That gamete cell must be used to make an embryo that lives to reproduce and whose genome fixates into the population at random location in the genome. This rare event is usually species specific. Here are two examples (ones that aren't among those found at the Wiki that I liked at the start of this bullet point):
- Pseudogenes -- Shared errors are a powerful argument for a common source. If two books describe the same concept in similar language, it's possible they just both converged on the same wording. However, if they both share the same grammar or spelling errors it becomes improbable to assume that they did not derive from a common source. There are genes that no longer code for a protein due to a mutation or error. Species often share the same pseudogene with the same inactivating mutation. A famous example of this is the L-gulonolactone oxidase that synthesizes vitamin C. All simians including humans share one pseudogene of inactivated L-gulonolactone oxidase, but the guinea pig has a different pseudogene indicating a different mutation.
- Embryology -- The pharyngula stage of embryonic development appears to be highly conserved. At this stage, it is difficult to tell the difference between various vertebrate species. This conserved state screams common ancestry, and the field of evolutionary development has expanded our knowledge of developmental genes and their consequent embryo ontogeny to amazing levels of detail, all thanks to acknowledging common descent. (High level lecture notes on how embryology helps support the theory of evolution...from NYU.)
- Chromosome fusion - Gene fusion or chromosome fusion is when two chromosomes are spliced together. As an example, chimpanzees have one more chromosome than humans do. If the two species share a common ancestor, scientists should be able to figure out what happened to that chromosome. Researchers have found that chromosome 2 in humans is actually the fusion of two separate chimpanzee chromosomes. At the end of each chromosome is a marker called a telomere, which usually appears only on the ends. In human chromosome 2 it also appears in the center, marking where the two ends fused. (This concept is perfectly well explained in layman's terms in the Ken Miller video above.)
- Convergence -- The phylogenetic trees constructed using anatomical homology, DNA homology, pseudogenes, endogenous retroviral insertions, and many other methods all converge on a similar looking tree. There are slight differences but the general relationships of the trees are intact. If any of these methods were flawed, they would not converge on the same tree. (Examples of convergence....and for folks who like pictures and text, this is a good alternative to the Wiki linked at the start of this bullet.)
- For scholarly articles on convergences, I suggest beginning here. Several additional scholarly sources discussing the matter -- in particular, identifying and discussion case after case of the theory of evolution's predictions re: convergence with regard to myriad life forms -- are in the references section at the the end of the paper.
- Uniqueness -- The complex, predictive patterns of similarities and differences in the world of life have have a unique known explanation - no one has even hypothesized an alternative account for the patterns exhibited - either there is common descent or there is something which is somehow simulating common descent.
Understanding the Creationists' Arguments Against Common Evolutions' Predictive Capability
Some creationists have claimed that true science must make predictions, but evolution only describes what happened in the past, so it is not predictive. However, this argument has several flaws:
- The argument is non sequitur. Evolution can be predictive, and yet still only describe what happened in the past. We do not have omniscient knowledge of the past, so we use the theory of evolution to make very specific predictions about what has already occurred and then we go looking to find out if the prediction is in fact what we find is/was so. While this may sound nonsensical on its face, we make predictions about the past all the time in day-to-day life: "If he hadn't had car trouble he'd have been on time", for instance.
- Many predictions are possible based on the theory of evolution (e.g., predicting germ/pest resistances to antibiotics/pesticides, predicting general traits/locations of future fossil finds, predicting population responses to selective breeding attempts, etc.)
- Just like meteorology only predicts effectively maybe a week into the future, evolution cannot be used to precisely predict what will happen in the future. It does, however, tell us what kind of changes can be expected to happen.
- There are many predictions concerning the future that can be extrapolated from the theory of evolution even if they are not explicitly stated by Darwin. Here are some examples of predictions that one could argue would be extrapolated from the theory of evolution.
- Species with high reproductive rates will have a better chance of surviving environmental change than species with low reproductive rates.
- Species from a common gene pool separated into group A and group B and isolated for generations over a longer period of time and exposed to different environmental conditions will eventually become unable to reproduce with members of the other group.
- It is possible to predict the outcome of a macro-evolutionary experiment, but it's a bit difficult to verify it. However, it is equally possible and valid to predict certain paleontological findings. Some of these are actually verified by now (like some kinds of fossils).
- Darwinian evolution predicts that all organisms on Earth derive from a common ancestor. This ancestor has not been identified through fossil records (and probably cannot be), but its existence is a necessary consequence of the fundamental genetic unity of all life on Earth.
- Creationists who use this argument fail to realize that there have been no testable/falsifiable scientific predictions made by Scientific Creationism.
- Evolution requires a huge amount of time to operate and thus effectively predicted that the Sun was powered in a far more efficient manner than previously thought — a prediction that was verified by the discovery of nuclear fusion. Even though evolution takes a long time to "do its thing," there are examples of it happening right before our eyes.
- Mendeleev only described what had happened in the past when devising the periodic table. One prediction of evolution, amongst others, was that transition species would be found and added to the fossil record, as they have been.
Notes:
- "More intelligent" does not mean "intelligent." It merely means more intelligent than something than something else that may or may not be intelligent in its own right.
- The cited Darwin quote is one Creationists, specifically those who espouse "intelligent design," just love to cite in making their "irreducible complexity" lines of argumentation.
- The point of the videos' inclusion at this point in the post is to show the predictive relevance and ability of the theory of evolution....please focus on that in particular when watching them...I realize that I could have included them in other parts of this discussion.
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