A1: This is essentially mandated by Wikipedia's official neutral point of view policy. This policy requires that articles treat views on various subjects proportionally to those views' mainstream acceptance in the appropriate academic field. For example, if two contradictory views in physics are held by roughly an equal number of physicists, then Wikipedia should give those views "equal time". On the other hand, if one view is held by 99% of physicists and the other by 1%, then Wikipedia should favor the former view throughout its physics articles; the latter view should receive little, if any, coverage. To do otherwise would require, for example, that we treat belief in a Flat Earth as being equal to other viewpoints on the figure of the Earth.

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 Rejection of evolution by religious groups give major coverage to these opposing views, while biological articles such as Evolution do not.

A2: As noted above, evolution is at best only controversial in social areas like politics and religion. The fact that evolution occurs and the ability of modern evolutionary theory to explain why it occurs are not controversial amongst biologists. Indeed, numerous respectable scientific societies, such as the American Association for the Advancement of Science and the National Academy of Sciences, have issued statements supporting evolution and denouncing creationism and/or ID.^[1] In 1987 only about 0.15% of American Earth and life scientists supported creationism.^[2]

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.

A3: That depends on if you use the words evolution, theory, and fact in their scientific or their colloquial sense. Unfortunately, all of these words have at least two meanings. For example, evolution can either refer to an observed process (covered at evolution), or, as a shorthand for evolutionary theory, to the explanation for that process (covered at modern evolutionary synthesis). To avoid confusion between these two meanings, when the theory of evolution, rather than the process/fact of evolution, is being discussed, this will usually be noted by explicitly using the word theory.

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.

A4: Once again, this depends on how one is defining the terms proof and proven. Proof has two meanings: in logic and mathematics, it refers to an argument or demonstration showing that a proposition is completely certain and logically necessary; in other uses, proof refers to the establishment and accumulation of experimental evidence to a degree at which it lends overwhelming support to a proposition. Therefore, a proven proposition in the mathematical sense is one which is formally known to be true, while a proven proposition in the more general sense is one which is widely held to be true because the evidence strongly indicates that this is so ("beyond all reasonable doubt", in legal language).

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.

A5: Evolution, as a fact, is the gradual change in forms of life over several billion years. In contrast, the field of evolutionary biology is less than 200 years old. So it is not surprising that scientists did not directly observe, for example, the gradual change over tens of millions of years of land mammals to whales.^[3] However, there are other ways to "observe" evolution in action.

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.^[4] 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.^[5][6] Evolution has also been observed in the field, such as in the plant Oenothera lamarckiana which gave rise to the new species Oenothera gigas,^[7] in the Italian Wall Lizard,^[8] and in Darwin's finches.^[9]

Scientists have observed significant 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.^[3] So, although the entire evolutionary history of life has not been directly observed, all available data supports the fact of evolution.

A6: The article doesn't equate the two, but merely recognizes that they are largely or entirely the same process, just on different timescales. The great majority of modern evolutionary biologists consider macroevolution to simply be microevolution on a larger timescale; all fields of science accept that small ("micro") changes can accumulate to produce large ("macro") differences, given enough time. Most of the topics covered in the evolution article are basic enough to not require an appeal to the micro/macro distinction. Consequently, the two terms are not equated, but simply not dealt with much.

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.

A7: To be frank, there isn't any. Most claimed "evidence against evolution" is either a distortion of the actual facts of the matter, or an example of something that hasn't been explained yet. The former is erroneous, as it is based on incorrect claims. The latter, on the other hand, even when accurate, is irrelevant. The fact that not everything is fully understood doesn't make a certain proposition false; that is an example of the argument from ignorance logical fallacy. Examples of claimed evidence against evolution:

1. 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.^[10][11]

2. 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.^[12][13]

3. 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.^[14] 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.^[15][16]

4. 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.^[17][18]

With regard to the Wikipedia Evolution article, if there is any evidence against evolution, it has yet to be accepted by any peer-reviewed scientific publication. This means that even if every editor on Wikipedia knew that there was evidence against evolution, we could not add that information to the article without violating Wikipedia's official policies of no original research and neutral point of view. Whether editors think that evolution has evidence against it or not is irrelevant; what matters are the noteworthy scientific views on this issue.

A8: If by "arise", one means "develop from non-organic matter through abiogenesis", then this is a question that is not answered by evolutionary theory. Evolution only deals with the development of pre-existing life, not with how that life first came to be. The fact that life evolves is not dependent upon the origin of life any more than the fact that objects gravitate towards other objects is dependent upon the Big Bang.

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.