Is there/Can there ever be a credible scientific alternative to Darwin’s theory of evolution?
In principle, yes, but in actual practice, evolution has built up such a tremendous mountain of evidence that it’s exceedingly unlikely.
If there’s enough observable evidence that tends to refute the current theory of evolution and/or support another theory better than the existing body of evidence supports the theory of evolution, then the answer is yes, there could be a scientifically credible alternative.
Given the rather large, consilient body of evidence that backs the current theory of evolution, it would take a great number of amazing discoveries before we’d have to abandion the current theory of evolution altogether.
There could be a number of potentially viable hypotheses, but they may by definition or other constraints unfalsifiable - Last Thursdayism and Universe-as-simulation, for example - AFAIK, there’s no particular reason these must be wrong, but there’s no way to tell, so they’re not likely to emerge as scientific theories.
Right now, descent with modification seems to match what we have observed about populations well enough to satisfy Occam’s Razor, but is is alway possible that something may be uncovered that shows that “Darwin’s theory of evolution” is as limited as Newtonian physics.
It should be clarified what exactly you mean by “Darwin’s Theory of Evolution.”
That evolution has occurred during the history of the Earth not a theory, but a fact (to the extent that any facts exist in science), attested to by many independent lines of evidence, including paleontology, comparative anatomy, genetics, development, and biogeography. That evolution has occurred has been recognized by scientists since well before Darwin. That this very large body of empirical evidence would be overturned is virtually impossible.
“Darwin’s Theory of Evolution” refers to the mechanism by which evolution occurs, which Darwin postulated to be natural selection, rather than to the fact that evolution has occurred in the past. There is a large amount of empirical and theoretical evidence that natural selection is the principle mechanism for evolutionary change, although it is now recognized that other factors such as genetic drift can also play a role.
What Colibri said.
A scientific theory is generally not just one idea – most of what Darwin proposed 151 years ago consisted of ideas that, to one extent or another, were understood and accepted already. What Darwin did was to consolidate all of this knowledge under one umbrella so that it explained all of the diversity of life on Earth.
Like other great theories, it provided more than explanations of what was known, it led to predictions about what would be known and created new paths for research that would follow – descent with modification suggests that there is information to be passed along, a mechanism for passing along that information, and a physical form for that information to take. Less than a century later scientists have isolated DNA.
Someone once described a scientific theory as a table – a flat surface on which you can build things. A table with only a few legs is unstable. Theories like evolution and plate tectonics are supported by hundreds, thousands of legs. Some of those legs may indeed be weaker than others, but you pretty much have to knock all of them out to destabilize the entire structure.
There can be and there are alternatives to Darwin’s theory (although those alternatives generally reject only some aspects of Darwin). Darwin contemplated a gradual, continuous process of evolutionary change, sometimes referred to as gradualism. In practice, however, species tend to be relatively stable for long periods of time, then evolutionary change is seen during a relatively compressed period. Several theories reject gradualism, with the most famous being Stephen Jay Gould’s theory of punctuated equilibrium.
Note that this does not mean that there is a scientific alternative to evolution itself. As Colibri points out, evolution is an observed fact.
Lolcats have too much influence.
I read the opening sentence of the OP as “Is there can be a…”
Not really. A handful of scientists (in a loose sense of that word) had suggested that present life-forms have evolved from earlier ones before Darwin, but it was Darwin (and Wallace) who first marshaled the evidence to make a persuasive case that it had actually happened. Indeed, Darwin’s evidence for this was actually inconsistent with what was by far the best developed earlier evolutionary theory, Lamark’s (which envisaged independently evolving lineages of organisms, that never go extinct or diverge, but just change over time into different forms), and did not really bear on the other earlier accounts of evolution, such as those of Erasmus Darwin and Chambers, because they were simply too vague to make any falsifiable predictions.
You are right to distinguish between the issue of evolution having actually happened (in the Darwinian pattern, with organisms diverging from common ancestors, with some species going extinct) and the issue of the mechanism, such as natural selection, through which it happens, but Darwin actually deserves the credit for discovering both of these (along with Wallace, who also, independently, discovered them both). In fact, it took Darwin a couple of years [warning: exact time-line subject to vagaries of my memory] to come up with natural selection theory after he had realized that evolution must be happening. (After which, of course, he waited 20 years before telling anyone about any of it.:rolleyes:)
As you rightly say, the evidence that evolution has happened is overwhelming, but I think it is fair to say that the evidence that natural selection (including sexual selection) occurs is pretty overwhelming too. The only issue really potentially open is whether there are any additional mechanisms driving evolution besides the currently known ones of natural selection and random genetic drift. It seems conceivable that there might be other significant mechanisms involved alongside these, but it does not seem very likely.
Although Darwin advocated gradualism, it is not an essential component of his theory. The key element is natural selection; it was Wallace’s independent formulation of this principle that finally forced Darwin to publish his ideas. Eldredge and Gould’s ideas about punctuated equilibrium (Niles Eldredge was actually the first author on the seminal paper) assumed that natural selection was still one of the principle mechanisms of evolutionary change; it was basically an extension of Mayr’s ides about allopatric speciation to paleontology.
The OP didn’t say if the question was based on possible mechanisms in isolation, or if based on the existing genetic, fossil and geologic evidence.
Since everyone else has given the answer to the latter possibility, what if we just consider mechanisms by which changes to the genome might have occurred. Darwin wrote about, and was inspired by, the human breeding of plants and animals in order to filter out unwanted characteristics and get new ones. In this case we have natural variations in characteristics occurring, but unnatural selection. Today, and in the future, we can also modify characteristics unnaturally, through genetic engineering, and also select ourselves.
There is nothing unscientific about either of these mechanism, and I’d say that descent with modifications using them would still count as evolution. What is unscientific is insisting this sort of directed evolution happened in the history of the Earth without a shred of evidence.
True that Darwin compiled all the evidence and made it into a cohesive case (and that was his other main contribution, in addition to the idea of natural selection). However, I think the idea of descent with modification went beyond “a handful of scientists,” but was considered plausible by many. The main difficulty was that a credible mechanism had not yet been proposed. To some extent it was like the situation with “continental drift” before the mechanism of sea-floor spreading was discovered and turned it into plate tectonics. (However, I think that there were more biologists that believed in descent with modification before The Origin of Species than those that gave credence to continental drift before plate tectonics.)
There is, as I understand, another kind of evolution that works differently from natural selection, based on epigenetics. If a man in his youth is for example starved, and later reproduced, his descendants will have different metabolism for several generations to come. The mechanism involves some thing or another around or on top of DNA; it isn’t just a weakening, but rather an inherited response mediated by an information storage system that is kind of parallel to the DNA system operating with natural selection. In this example, there is no selection effect, but rather a new difference inherited from the individual who went through the starvation.
If anybody can clarify or correct this, please do!
A study of Dutch mothers showed that the grandchildren of individuals who had undergone famine during WWII were relatively underweight. The mechanism of transfer is evidently the acquired pattern of methylation of the DNA.
Certainly there are other factors that can be significant in evolution other than natural selection, but selection still seems to be the most important.
I know of a few evolutionists - the ones who REALLY like genetic drift - that would quibble with that, but yeah.
I’ve known a few that pushed developmental constraints and other factors as being more important, but as a general thing most accept natural selection as primary.
If there’s one thing I’ve learned about biology, it’s that biology is messy.
Natural selection does not need DNA (which should be obvious since Darwin could describe it without reference to DNA), but only heritable traits. To take it to the extreme, if we found life on Mars that did not have DNA, but used some other method of encoding information, biologists would not claim Darwinian natural selection was falsified.
And variation in the inherited traits of the offspring, from sexual reproduction and/or mutation. If all descendants were exact copies of their parents, there would be no evolution.
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