Is natural selection a tautology, and therefore not truly falsifiable?

Question

I've heard the argument from a lot of creationists that all the evidence for natural selection (and by extension, evolution) in general is worthless because natural selection is so flexible that it could cover all the data, no matter what we discovered. In essence, that natural selection is a tautology:

Survival of the fittest. What is 'fit'? What survives.

There are other creationists, however, that admit that natural selection could be falsified. These are split into two groups:

• The ones that say, if you rephrase natural selection as a non-tautology, it becomes obvious that it doesn't work:

Natural selection has been criticized as a tautology. This would be a major problem for evolutionary biology, if true, because tautological statements can't be falsified and, therefore, can't be scientific. There is merit to this critique insofar as the theory of natural selection is indeed generally described in a tautological manner. However, natural selection can be described non-tautologically if we’re careful. Natural selection should be defined as the theory that attempts to predict and retrodict evolutionary change through environmental forces acting upon organisms. However, this re-framing comes at a cost: it reveals, based on our current knowledge of evolutionary forces, the lack of ability to make accurate predictions about expected changes except in the most simple of circumstances.

• And those that say that the falsifying options provided by natural science are impossible to actually use. Here are some of those falsifying options:

1. Charles Darwin himself proposed a rather strong test of evolution: "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down." [Darwin1859, pg. 175]. This is the basis of claims by various intelligent design writers that various biological structures, such as the vertebrate immune system or the bacterial flagellum, are "irreducibly complex" -- they consist of multiple components that could not develop in the absence of the others. However, these structures have been exhaustively studied in the scientific literature, and scientists have demonstrated entirely plausible evolutionary pathways. See Complexity.

1. Famed biologist J. B. S. Haldane, when asked what evidence could disprove evolution, mentioned "fossil rabbits in the Precambrian era" [Ridley2004, pg. 66]. This is because mammals, according to current scientific analysis, did not emerge until approximately 40 million years ago, whereas the Precambrian era is prior to approximately 570 million years, when only the most primitive organisms existed on earth.
2. Biologists had long conjectured that human chromosome number two was the result of a fusion of two corresponding chromosomes in most other primates. If DNA analysis of these chromosomes had shown that this was not the case, then modern evolutionary theory would indeed be drawn into question. This "fusion hypothesis" was indeed confirmed, rather dramatically, in 1993 (and further in 2005), by the identification of the exact point of fusion. For additional details see DNA.
3. Modern DNA sequencing technology has provided a rigorous test of evolution, far beyond the wildest dreams of Charles Darwin. In particular, comparison of DNA sequences between organisms can be used as a measure of relatedness, and can further be used to actually construct the most likely "family tree" hierarchical relationship between a set of organisms. Such analyses have been done, and the results so far dramatically confirm the family tree that had been earlier constructed solely based on comparisons of body structure and biochemistry. For additional details see DNA.

Is there any way to save natural selection? To do so, we need to:

• Prove it can be explained non-tautologically
• Prove that it does make useful predictions
• Give falsifying experiments that are reproducable and actually possible.

Answer 1

I think @Remi.b's answer is great and really the only way to answer your questions is with a comprehensive introduction to evolution. However, I wanted to address the tautology issue more directly.

First, the "survival of the fittest" seems like a tautology with "natural selection" because it is not a description of how natural selection works, rather, it is a phrase meant as a synonym for natural selection, to help describe the result to someone unfamiliar with the phrase.

Let me use an analogy: it would be like if you were a very new learner of English, and I told you "Joe's truck has more mass than an elephant!"

If you aren't really familiar with the term "mass" in English, this phrase could be confusing. So I explain instead that "Joe's truck is heavier than an elephant." If you know the word "heavy" this is easier to understand.

However, there is a tautology there! the car is actually heavier because it has more mass, but that does not make either phrase untrue or untestable: it's just another way of saying the same thing within a context (i.e., those statements are the same if they are exposed to the same gravity).

The testable hypothesis that natural selection makes is that, given 2 things: 1) a population where individuals have traits that give them different chances of survival, and 2) some way for offspring to inherit traits from their parent(s), then the population over time will consist of individuals who are more likely to possess the traits that gave a high chance of survival.

Following this, should the environment change in some way such that a different trait is now beneficial, that trait will increase in prevalence.

There are way too many experiments to summarize here that show 1), 2), and a combination of 1) and 2), as well as experiments that show that indeed, when you have 1) and 2) you get natural selection.

Answer 2

The tautology argument is an attack on a rare phrasing and not on the nature of the theory of evolution.

First, the theory of evolution is way more than just natural selection but let's ignore that for the moment.

The phrasing 'Survival of the Fittest' was first suggested by Herbert Spencer and was later used by Darwin when he changed the title of the fourth chapter from "NATURAL SELECTION" to "NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST" (Thanks @BryanKrause for his comment).

It is before all a labelling. A catchy sentence to refer to the process of Natural Selection. In no way does it mean that Natural Selection is a non-sensical explanation.

Natural Selection is easy enough to understand for a layman that you can make you own opinion

Luckily, the concept of Natural Selection is really easy to understand. It does not take any a priori knowledge in Science to understand it and if you have a look at any intro course to evolutionary biology you will understand it yourself.

There are thousands of good sources of information on the subject online. If you want to learn about it, do not look at straw man and other fake explanations from creationist (and other religious extremist) websites! Consider for example Understanding Evolution or many of our posts on Biology.SE such as this one for example. You can also get any intro text book (see here for recommendations).

How does natural selection work?

Here is a copy paste of my answer here. It explains the very basic concept of natural selection through the so-called Lewontin recipe and gives a somewhat silly, but easy, example with a population of pens!

The Lewontin recipe says that natural selection occurs whenever:

1. Individuals in a population varies in terms of a given trait
2. This trait has some (additive) heritability. Here is one of the several posts that explain the concept of heritability. It might be slightly a post that is a bit advanced for you though but shortly speaking it means that offspring are more similar to their parents more than they are to other non-kin individuals in the population.
3. The fitness varies (not necessarily linearly) as the trait varies.

Simple example:

1. In a population, there are blue pens and red pens
2. Reproduction is asexual and blue pens create other blue pens while red pens create other red pens.
3. blue pens make more offspring than red pens.

Of course, there exist strict mathematical formulations of this process that you can learn in any introduction to evolutionary genetics.

Your questions

Note that your questions are all way too broad for a single post (and your question could be closed as too broad) but I wanted to try to give you a hand anyway.

Prove it can be explained non-tautologically

There is no "proof" in science, only evidence. But let's ignore that for the moment.

Please have a look at any intro course to evolutionary biology (see above).

Prove that it does make useful predictions

Please have a look at any intro course to evolutionary biology (see above). Afterward, you can eventually have a look at Is evolution a predictive theory?.

Give falsifying experiments that are reproducable and actually possible.

Please have a look at Demonstrable and repeatable examples of evolution which lists thousands of evidences explained in layman terms.

There are thousands (tens of thousands maybe?) of papers published every year extending our understanding of evolutionary processes! It is hard to know which one you would be interested in!

Related post

You should have a look at Is evolution a fact?

Answer 3

Natural selection is an observation, not a tautology. We can certainly imagine worlds - call them Disney ecologies (or for the religiously inclined, Gardens of Eden) - in which natural selection simply doesn't happen. E.g. each species is independently created, and each pair of a species has exactly two offspring before dying of old age.

This is easy enough to imagine, just as it's easy to imagine a flat Earth enclosed in a dome of "firmament" but it simply doesn't match what we observe happening in the world we live in.

Answer 4

Surprisingly, there seems to not have been any mention of Karl Popper, who famously argued that Darwinism is tautological and not testable/falsifiable. This answer will just give some quotes from Popper:

1963:

There is a difficulty with Darwinism. While Lamarckism appears to be not only refutable but actually refuted (because the kind of acquired adaptations which Lamarck envisaged do not appear to be hereditary), it is far from clear what we should consider a possible refutation of the theory of natural selection. If, more especially, we accept the statistical definition of fitness which defines fitness by actual survival, then the theory of the survival of the fittest becomes tautological, and irrefutable

1965:

the trouble about evolutionary theory is its tautological, or almost tautological, character: the difficulty is that Darwinism and natural selection, though extremely important, explain evolution by 'the survival of the fittest' (a term due to Herbert Spencer). Yet there does not seem to be much difference, if any, between the assertion 'those that survive are the fittest' and the tautology 'those that survive are those that survive'. For we have, I am afraid, no other criterion of fitness than actual survival, so that we conclude from the fact that some organisms have survived that they were the fittest, or those best adapted to the conditions of life.

This shows that Darwinism, with all its great virtues, is by no means a perfect theory. It is in need of a restatement which makes it less vague.

1969:

Biologists (especially Fisher) felt compelled to define as “more fit” those which more often survive. Thus, what once looked like a promising explanatory theory becomes quite empty. The statement “Evolution tends to produce higher forms because only the fittest survive” may sound like an explanation. But if we substitute here for “the fittest” its defining phrase, we get: “Evolution tends to produce higher forms because those forms which more often survive more often survive.” So our “because” phrase has degenerated into a tautology. But tautology cannot explain anything. All tautologies are equivalent to “All tables are tables” or “Those who live long are those who live long.”

1972:

A central problem of evolutionary theory is the following: according to this theory, animals which are not well adapted to their changing environment perish; consequently those which survive (up to a certain moment) must be well adapted. This formula is little short of tautological, because ‘for the moment well adapted’ means much the same as ‘has those qualities which made it survive so far.’ In other words, a considerable part of Darwinism is not of the nature of an empirical theory, but it is a logical truism

1974:

the theory of natural selection is not a testable scientific theory, but a metaphysical research programme

1974:

Adaptation or fitness is defined by modern evolutionists as survival value, and can be measured by actual success in survival: there is hardly any possibility of testing a theory as feeble as this

For more details & discussion, see "Popper’s Shifting Appraisal of Evolutionary Theory" (2017).

Answer 5

The "survival of the fittest" statement which Darwin recommended as the best formulation of his idea of "natural selection" is definitely a tautology because there is no other operational definition of fitness besides survival (or reproduction). So, survive (reproduce) are those who survive(reproduce).

Darwin naively attempted to imitate the process of selection of domesticated species assuming that new species are produced by "natural selection" in the same way as dogs are produced from wolves. The poor guy was probably not familiar with the facts: the species produced by selection are inferior to the original ones. Dogs are inferior to wolves since they lost a lot of vital features. Moreover, this loss of information is irreversible: you cannot produce a wolf from a spaniel by selection.

In an abstract form, it is quite simple. There is a law: the complexity of a result of a selection algorithm cannot exceed the complexity of the algorithm. Therefore, any selection results in the information loss, and no new information can be produced by selection.