It provides responses for certain topics repeatedly brought up on the talk page. Providing similar answers each time a topic is brought up uses up many editors' time and energy. The FAQ addresses these common concerns, criticisms, and arguments, and answers various misconceptions behind them.
These FAQ answers reflect the decisions found in the talk page archives. Please feel free to change them in light of new discussion.
Many of these questions are rephrased objections to evolution that users have argued should be included in the text of Evolution. The reason for their exclusion is discussed below.
The main points of this FAQ can be summarized as:
- The process and theory of evolution are both uncontroversial among biologists.
- Wikipedia:Neutral point of view requires that minority views not be given undue emphasis.
- Therefore it is against Wikipedia policy for views without scientific support, such as all known objections to evolution, to be interjected into a science article like Evolution.
More detail is given on each of these points, and other common questions and objections, below.
Due to the enormous mainstream scientific consensus in support of modern evolutionary theory, and pursuant to Wikipedia's aforementioned policies, the Evolution article references evolution as an observable natural process and as the valid explanation for the diversity of life on Earth. Although there are indeed opposing views to evolution, such as Creationism, none of these views have any support in the relevant field (biology), and therefore Wikipedia cannot, and should not, treat these opposing views as being significant to the science of evolution. On the other hand, they may be very significant to sociological articles on the effects of evolutionary theory on religious and cultural beliefs; this is why sociological and historical articles such as Creation–evolution controversy give major coverage to these opposing views, while biological articles such as Evolution do not.
Thus, as a consequence of Wikipedia's policies, it is necessary to treat evolution as mainstream scientific consensus treats it: an uncontroversial fact that has an uncontested and accurate explanation in evolutionary theory. There are no scientifically supported "alternatives" for this view.
However, while the overall theory of evolution is not controversial in that it is the only widely-accepted scientific theory for the diversity of life on Earth, certain aspects of the theory are controversial or disputed in that there actually are significant disagreements regarding them among biologists. These lesser controversies, such as over the rate of evolution, the importance of various mechanisms such as the neutral theory of molecular evolution, or the relevance of the gene-centered view of evolution, are, in fact, covered extensively in Wikipedia's science articles. However, most are too technical to warrant a great deal of discussion on the top-level article Evolution. They are very different from the creation–evolution controversy, however, in that they amount to scientific disputes, not religious ones.
Evolution is not a theory in the sense used on Evolution; rather, it is a fact. This is because the word evolution is used here to refer to the observed process of the genetic composition of populations changing over successive generations. Because this is simply an observation, it is considered a fact.
Fact has two different meanings: in colloquial usage, it refers to any well-supported proposition; in scientific usage, it refers to a confirmed observation. For example, in the scientific sense, "apples fall if you drop them" is a fact, but "apples fall if you drop them because of a curvature in spacetime" is a theory. Gravity can thus either refer to a fact (the observation that objects are attracted to each other) or a theory (general relativity, which is the explanation for this fact). Evolution is the same way. As a fact, evolution is an observed biological process; as a theory, it is the explanation for this process. What adds to this confusion is that the theory of evolution is also sometimes called a "fact", in the colloquial sense—that is, to emphasize how well supported it is.
When evolution is shorthand for "evolutionary theory", evolution is indeed a theory. However, phrasing this as "just a theory" is misleading. Theory has two different meanings: in colloquial usage, it refers to a conjecture or guess; in scientific usage, it refers to a well-supported explanation or model for observed phenomena. Evolution is a theory in the latter sense, not in the former. Thus, it is a theory in the same sense that gravity and plate tectonics are theories. The currently accepted theory of evolution is known as the modern evolutionary synthesis.
In the first sense, the whole of evolutionary theory is not proven with absolute certainty, but there are mathematical proofs in evolutionary theory. However, nothing in the natural sciences can be proven in the first sense: empirical claims such as those in science cannot ever be absolutely certain, because they always depend on a finite set of facts that have been studied relative to the unproven assumptions of things stirring in the infinite complexity of the world around us. Evolutionary science pushes the threshold of discovery into the unknown. To call evolution "unproven" in this sense is technically correct, but meaningless, because propositions like "the Earth revolves around the Sun" and even "the Earth exists" are equally unproven. Absolute proof is only possible for a priori propositions like "1 + 1 = 2" or "all bachelors are unmarried men", which do not depend on any experience or evidence, but rather on definition.
In the second sense, on the other hand, evolutionary theory is indeed "proven". This is because evolution is extremely well supported by the evidence, has made testable confirmed predictions, etc. For more information, see Evidence of evolution.
Scientists have directly observed and tested small changes in forms of life in laboratories, particularly in organisms that breed rapidly, such as bacteria and fruit flies. A famous experiment was developed in 1992 that traced bacterial evolution with precision in a lab. This experiment has subsequently been used to test the accuracy and robustness of methods used in reconstructing the evolutionary history of other organisms with great success. Evolution has also been observed in the field, such as in the plant Oenothera lamarckiana which gave rise to the new species Oenothera gigas, in the Italian Wall Lizard, and in Darwin's finches.
Scientists have observed large changes in forms of life in the fossil record. From these direct observations scientists have been able to make inferences regarding the evolutionary history of life. Such inferences are also common to all fields of science. For example, the neutron has never been observed, but all the available data supports the neutron model.
The inferences upon which evolution is based have been tested by the study of more recently discovered fossils, the science of genetics, and other methods. For example, critics once challenged the inference that land mammals evolved into whales. However, later fossil discoveries illustrated the pathway of whale evolution. So, although the entire evolutionary history of life has not been directly observed, all available data supports the fact of evolution.
A more nuanced version of the claim that evolution has never been observed is to claim that microevolution has been directly observed, while macroevolution has not. However, that is not the case, as speciations, which are generally seen as the benchmark for macroevolution, have been observed in a number of instances.
- There aren't any transitional fossils, or there aren't enough.
- There are many transitional fossils, including Archaeopteryx (earliest and most primitive bird known), Thrinaxodon (a cat-sized mammal-like "reptile"), Tiktaalik (fish with many features akin to those of four-legged animals), Acanthostega (first vertebrate animal to have recognizable limbs), and Ambulocetus (early whale that could walk as well as swim). See also List of transitional fossils. That there are not more is explained by the rarity of fossilization and by punctuated equilibrium. Furthermore, technically all fossils are transitional fossils, because no species is fixed and unchanging. For example, you can argue that Homo erectus is a transitional fossil between Homo sapiens and Homo habilis. But in the same line of thought, you can say Homo habilis is a transitional fossil between A. afarensis and Homo erectus, and so on.
- Evolution violates the second law of thermodynamics, "the entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium".
- Organisms are not isolated systems. Rather, they are open systems; they exchange energy with their environment, and thus their entropy can either increase or decrease. Specifically, the main fuel source for evolution is the Sun, which is continually adding energy to the Earth ecosystem. See also Entropy and life.
- Evolution can't create "irreducibly complex" structures like the eye, or the bacterial flagellum.
- Both the vertebrate eye and the bacterial flagellum are well understood to have evolved from simpler structures. Indeed, simpler eye-like structures (such as the sea squirt's ocellus) can still be found in existing species. Complex biological traits can also evolve as exaptations, where ancestral structures that evolved for different reasons become coopted for new functions. "Irreducible complexity" is, in any case, neither a scientific concept nor a coherent argument: A less than full understanding of the evolutionary history of a biological structure is not evidence against evolution, any more than a less than full understanding of the gravitational orbit of every astronomical body is evidence against gravity. The empirical evidence for evolution is substantial, whereas no evidence has ever been provided for irreducible complexity.
- Evolution can't create new information.
- New information is created every time a mutation occurs. Even random "noise" is a form of information. (This random information is then non-randomly propagated by natural selection.) Examples of the evolution of completely new information include the enzymes of nylon-eating bacteria, which can digest nylon, a polymer that didn't exist before 1935.
On the other hand, if by "arise" one means "evolve into the organisms alive today", then the simple answer is: it didn't. Evolution does not occur "by chance". Rather, evolution occurs through natural selection, which is a non-random process. Although mutation is random, natural selection favors mutations that have specific properties—the selection is therefore not random. Natural selection occurs because organisms with favored characteristics survive and reproduce more than ones without favored characteristics, and if these characteristics are heritable they will mechanically increase in frequency over generations. Although some evolutionary phenomena, such as genetic drift, are indeed random, these processes do not produce adaptations in organisms.If the substance of this objection is that evolution seems implausible, that it's hard to imagine how life could develop by natural processes, then this is an invalid argument from ignorance. Something does not need to be intuitive or easy to grasp in order to be true.