Evolution

Not to be confused with "Evilution".

Basic Description

While the term is used in various ways, in this context "evolution" refers to change of inherited traits among reproductive populations over generations, which is summarily defined as "descent with [inherit genetic] modification" as coined by Charles Darwin. It is a natural phenomenon that encompasses the diversity of all life. One of the driving mechanisms behind this process is "natural selection".

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You cannot escape your own heritage.

The theory of evolution is the scientific model that explains how and why biological evolution occurs, as well as explaining the unity and diversity of life (not its origins) by concluding that every known species extant or extinct, is the result of evolution through common descent (and a few other processes such as "horizontal gene transfer" and "endosymbiosis"). As a result of the overwhelming evidence in favor of the theory, it represents the consensus of the scientists in the field of biology and science in general, thereby making it one of the strongest and well-supported theories in science. The theory of evolution is the very backbone of modern biology and understanding evolution has become a fundamental aspect in that particular field of science.

Understanding evolution (especially how it works) isn't easy. In order to adequately understand evolution, you need to have a basic understanding of many different things, including cellular biology, genetics, anatomy, geology, palaeontology, taxonomy, and more. It is a very complex subject and passing biology classes in college requires following many lessons on evolution, depending on what schools you are talking about. Many notable scientists throughout history have devoted their entire careers to this very subject, and many still do. Despite this, there are quite a few people who simply dismiss the entire scientific paradigm by asserting that evolution is "just a theory, not a fact" (among other asinine statements), as if they know better than every expert anywhere ever. The bulk of this category consists mainly of scientifically illiterate morons.

Etymology and Semantics

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Semantics: what every argument eventually boils down to.

Origin and Evolution of the Word

The word "evolution" (from the Latin root word "evolutio", meaning "to unroll" or the act of opening a book) traces its origins back to the 17th century when it was used to mean various things, including the description of physical movement, such as a tactical wheeling maneuver to realign the troops or ships. In early science, it was used as a synonym of "growth" and "development". Eventually the term came to be used in a more general way to describe progressive change. Ironically, Charles Darwin didn't prefer this word to describe the process of population level changes across generations. He used the phrases "transmutation by means of natural selection" and "descent with modification". Darwin used the word "evolution" only once in his book "On the origins of species".

"There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."

Contemporary scientists, such as Julian Huxley (aka Darwin's Bulldog), adopted that word and is still in use by scientists today as the accepted technical term, although scientists do use the word in differently at different times. Cosmologists often refer to the process of how stars are "born", change and "die" as "Stellar Evolution". Under this general and rather nebulous usage, "evolution" simply means "change over time".

Straw-man Definitions

Creationists often exploit semantics to misrepresent evolutionary theory. One infamous example is the "6 types of evolution" by Kent Hovind, wherein big bang cosmology, nucleosynthesis, stellar/planetary accretion, abiogenesis, and biological evolution are all erroneously lumped together under one banner called "evilution(ism)" as if they were all part of the same theory wherein "everything came from nothing without God". The creationists do this to create the illusion that their denial of science is limited to just one thing, not to multiple aspects of many different scientific theories spanning many independent fields of science. They also do this to make it seem like a person cannot accept biological evolutionary theory without also accepting all the other theories that they have equated with evolution, meaning that they must also accept that the Genesis isn't literal and that God doesn't exist, so a person cannot be a "true" christian and also accept evolutionary theory. This is obviously erroneous and is the 1st Foundational Falsehood of Creationism as stated by AronRa. Creationist attempts to straw-man evolution is an easy excuse to explain why most people have such a fucked-up view of what evolution is, but it isn't always their fault. Even popular media that seem to promote evolution as a positive, progressive thing such as "Pokemon", "The X-men" and various movies that use evolution as a plot device, only spread misconceptions more often than correct them.

The Modern Scientific Usage

Unless the context is specified to be something else, "evolution" refers to an aspect of population genetics - in which case, it is summarily defined as "Descent with Inherent [genetic] modification". Paraphrased for clarity,  

Evolution is a process of changing genetic (alleles) frequencies among reproductive populations over generations, which leads to changes in the morphology and/or physiology of descendant subsets. When compiled over many generations, these changes can expand biodiversity when increasing variation between genetically-isolated groups eventually lead to one or more descendant branches that are increasingly distinct from their ancestors and/or cousins. - Or if you prefer, the process by which life forms diversify via "descent with modification".

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That's right: language isn't intelligently designed either.

Such a definition, especially the short-hand version "change in allele frequencies within a population over time" (which is based on the Hardy–Weinberg principle) is, though very useful, not applicable to all cases. When dealing with evolution observed in the fossil record, where no change in genetic frequencies can be directly determined, the change in morphology is used. A broader definition can also be made that includes other processes that parallel the evolution of life forms, but don't involve life. Viruses are not considered to be alive, but they do reproduce and inherit genetic material with mutations, so they also can evolve. Self-replicating molecules have the potential to evolve as well, and is posited to be one factor that explains the origin of life. While evolution may be a part of abiogenesis by this broader definition, this isn't true the other way around (the assertion that abiogenesis part of evolution), since abiogenesis involves chemical processes that don't count as evolution. Other examples are computer programs such as genetic/evolutionary algorithms and how human language has changed. The evolution of language parallels the evolution of life almost perfectly such that it can be used as a very good analogy to explain to laymen what evolution is and how it works (see the figure above).

A Historical Overview

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Time table showing The History of Evolutionary Thought - from evolution.berkeley.edu

The idea that animals could descent from different animals (including humans) wasn't made-up by Charles Darwin. Earlier concepts of it existed, most of them were dead wrong and laughable compared to our current understanding, which is also true for the earliest concepts of other scienctific paradigms.

From Antiquity to Medieval Times

Greek philosophers proposed their own evolutionary ideas. One of them was the pre-Socratic Greek philosopher Anaximander of Miletus, who proposed that the first animals must have lived in water and that the first land-dwelling ancestors of humans would've been amphibious, spending most of their time in the water to give birth and partially to forage onto land. That was quite accurate, surprisingly so, especially considering that this man lived over 2500 years ago. However, more influential philosophers proposed that all things, not just living ones, were immutable by divine design according to Plato's essentialism, and Aristotle proposed that everything was part of a hierarchy called "scala naturae" (Great Chain of Being), sometimes erroneously called "the evolutionary ladder". This hierarchy was constructed according to the degree of "perfection", with "higher forms (of life)" at the top. Obviously, humans were put as the highest form among living things, just below divine beings. The Islamic world preserved these ideas and reintroduced them to medieval Europe, where these ideas were accepted by Christian thinkers, such as Thomas Aquinas, and later adapted to fit their theology by putting God on top of the scale and Hell at the bottom. Life forms were organized as species, each species occupied its own unique place on this scale. As it was believed that every species was created by God to be unchanging, species moving (or evolving) from its position to a higher or lower one wasn't considered as a possibility.

The Renaissance and Enlightenment

During and between the 16th and the 18th century, modern science emerged out of the major developments that were made by the intellectuals of that period, which is known as the "scientific revolution". These advancements had profound impact on how society viewed the world, sometimes pissing off the church, especially with this absurd notion that were are not the center of everything. Along the way, there were many scientists doing groundbreaking work that laid the foundation upon which evolutionary science would eventually be build. In 1543, Flemish anatomist Andreas Vesalius 1514-1564 published his book called "De humans corporis fabrica libri septem" (Latin: "On the fabric of the human body in seven books")- "Fabrica" for short. It showed many anatomical traits that humans shared with other animals with little unique traits remaining (which is true for any other animal), thereby making humans not so unique. In 1667, Danish scientist Nicolas Steno (original name: Niels Steensen) 1638-1686 published his work wherein he made the comparison of the shark teeth with fossils called "tongue stones". Based on this proposed that tiny particles in living material, such as shark teeth, could be replaced bit by bit period by tiny particles of minerals, and be preserved as rock without loosing its shape. In his book "Dissertationis prodromus" of 1669, Steno proposed four principles to explain how fossils could be embedded in deep layers of solid rock: 1) Law of superposition, 2) Principle of original horizontality, 3) Principle of lateral continuity and 4) Principle of cross-cutting relationships. This marked the beginning of paleontology and geology. In 1735, Carl Linnaeus (Carl von Linné) 1707-1778 published the first edition of his book "Systema Naturæ" wherein he introduced a two-word naming system of organisms called "binomial nomenclature", with the first identifying its genus and the second its species, because naming a tomato with 7 latin words is just absurd. In this book, he also established a system of classification called "Linnaean Taxonomy". Unlike the linear scale of the Aristotelian "great chain of being", Linnaean taxonomy was a "twin-nested" hierarchy, a system that looks like boxes within larger boxes, each box contained at least 2 smaller boxes and so on, based on characteristics shared by members of each box, called a taxon. This demonstrated that life isn't composed of separate "kinds" as modern creationists claim, which is ironic since Linnaeus was a christian creationist himself. Darwin recognized that this pattern of shared traits among different species that Linnaeus had discovered is exactly what evolution via common descent would produce (the twin nested hierarchy of taxonomy reflects a tree of life). To add insult to injury, Linnaeus classified humans as primates, more specifically alongside monkeys, and more specifically still, among the other apes, because there was (and there still is) no way to objectively classify humans outside the ape category, just like it is impossible to place humans outside the mammal or vertebrate category. In response to other scientists criticizing him for classifying them alongside these "damn, dirty apes", Linnaeus wrote (note: "simian" is another word for "monkey"):

"It does not please [you] that I've placed Man among the Anthropomorpha, perhaps because of the term 'with human form', but man learns to know himself. Let's not quibble over words. It will be the same to me whatever name we apply. But I seek from you and from the whole world a generic difference between man and simian that [follows] from the principles of Natural History. I absolutely know of none. If only someone might tell me a single one! If I would have called man a simian or vice versa, I would have brought together all the theologians against me. Perhaps I ought to have by virtue of the law of the discipline."

In 1749, the French naturalist Georges-Louis Leclerc, Comte de Buffon 1707-1788 published the first volumes of his encyclopedia called "Histoire Naturelle" (French for: Natural history). He wanted it to contain everything that was known about the natural world and its history. It wasn't just regurgitating things that were said by others, he tried to account for the evidence he knew of at that time based on the new (at that time) Newtonian physics. Discussing on the formation of the earth itself, and how mountains had arisen, he realized that the earth had to be allot older than just 6,000 years. He also argued that species were merely varieties, modified from an original form. In 1796, French naturalist George Cuvier (full name: Jean Léopold Nicolas Frédéric Cuvier) 1769-1832 published his paper on fossils of elephants comparing them with living elephants. Most people during that time, even the scientists believed that fossils were from (or the ancestors of) species that were still around in some remote part of the world, however within this paper Cuvier identified mammoths and mastodons as being distinct from anything that was alive. As he showed, these species just vanished from the face of the earth without leaving any living descendants. He was the first to show that extinction was a real natural phenomenon, which was one major shift in paradigms that established vertebrate paleontology. In 1798, political economist Thomas Robert Malthus 1766-1834 published his book "An Essay on the Principle of Population", wherein he demonstrated that humans couldn't multiply indefinitely without limit. He showed that the human population had the potential to increase its numbers in a geometric manner, doubling every 25 years or so. Of course, due to limited resources, homicides, plagues, etc population growth is kept in check. This brute fact of ecology was not only true for humans, but for any other species as well. The reason why we aren't overrun by flies due to the rate at which they produce is because most offspring die before they are able to reproduce in turn. Darwin recognized this as a universal "struggle for existence", which formed one of the key principles of his theory to explain why life evolves. In 1802, Jean-Baptiste (Pierre Antoine de Monet, Chevalier de) Lamarck 1744-1829 published his book "Recherches sur l'Organisation des Corps Vivants" (Research on the Organization of Living Bodies), wherein he put the first theory of evolution. He argued that organisms changed by "use and disuse" during its life and that these changes were passed on. The famous example of giraffes stretching their necks to reach leaves, often comes to mind. Lamarck's theory didn't involve common descent. He thought that each species first originated as simple forms by "spontaneous generation" and increased in complexity over many generations. To him, the rather "simple" microbes had recent origins and that the complex animals had evolved for a longer time. Despite many differences between it and Darwin's theory, Lamarck's pioneering works gave Darwin something to improve upon. In 1815, english geologist William Smith published his drawing of a nation wide geological map of britain showing its geological features. During his work to describe the geological features of his country, he saw that the fossils were arranged in a specific order among layers from top to bottom. The same pattern sequence of fossils in the rock layers occurred even at a different place as he traveled across England. Building upon the work of Nicolas Steno, Smith established Biostratigraphy or the geological column, which revealed different chapters in the history of life. As a result, the rock layers could be as a record for life forms that existed at different times, the older ons at layers below the younger ones. The record revealed clearly that life on earth changed throughout its history. In 1828, scientist Karl Ernst von Baer 1792-1876 worked on the comparison of embryological development of different animal species, arguing against Recapitulation, that development followed the linear progression from "lower" simpler form toward "higher" forms (reminiscent of the Great Chain of Being). Under recapitulation, humans would first become first, then ambiphians, then reptiles and then mammals before becoming humans. But von Baer recognized that development didn't follow a linear progression, but a divergent one. Humans didn't first develop wings or hooves, but the limbs of horses, birds and humans start out as limb buds (similar to each other) before starting their unique developmental path that makes them different. Darwin used this as evidence for common descent, since this pattern (just like in taxonomy) resembles a tree of life. The more closely related two organisms are, the more similar their development was and the more similar they would be in earlier stages in development, which is also true for organisms more distantly related. Humans and other tetrapods look allot like each other when they first develop their limb buds (as pointed out before), but in even earlier stages of development, they show similarities with the early developmental stages of fish as with their pharyngeal pouches (or Gill slits). In 1830-1833, geologist Sir Charles Lyell 1797-1875 published "principles of Geology" wherein he established the ideas made by scientists prior to him. One in particular was James Hutton, who argued that gradual geological processes operating over "deep time" explained the geological features he observed, not unimaginable catastrophes as most scientists believed at that time. Lyell expanded this idea by establishing the principle of uniformitarianism, that geological features are best explained as being the result of the same gradual processes that are observable today, only acting over very long periods of time. We can see rivers eroding rock, inch by inch, each year, which explains how large canyons are formed over a long period of time. These were very influential to Darwin since he adopted the same gradualism approach to his theory. If life evolves to adapt to the environment, and the environment changes by gradual processes, life must also evolve gradually in response.

Darwin's major contribution

One might think that Darwin had nothing original to say after reading what was previously said, but nothing could be more wrong. Rarely, a scientific advancement is made in isolation so of course, there were similar ideas proposed before Darwin came along. What Darwin did was taking this whole mess of distributed clues, that others before him have gathered, and put them together along with his own original work into a coherent frame work, aka a scientific theory.

Steve McRae's Preferred Definition for Discussional Purposes:

Evolution- The change of allele frequency, or heritable traits passed on, in any given population of species from one generation to the next.

Extras

MrIntelligentDesign's comments have been mirrored to his own page, due to its lack of scientific accuracy and coherency. (After MrID wrote the same thing for the second time after removal) Because this page is not intended to be a debate forum, his comments are removed again, but they are still on his own page, where people can still see it (so it isn't censorship). Sorry Edgar, do this on your own page or somewhere else. It doesn't belong here. (After MrID wrote the same thing again for the third time after removal) Dear Edgar, People can clearly see here above that you wrote something on this page. They can click on the link and see what you wrote, so you don't have to put your shit back on this page again and again. If you do place it here again, I will (unfortunately) private the page so that you will not be able to do it again until you accept that this page is not a place for you to pontificate. That's why you have your own page. Please don't force my hand.