Definition of the word evolution

Last Updated:
30 Mar 2023
— Updated example sentences

Evolution is a biological process. It is how living things change over time and how new species develop. The theory of evolution explains how evolution works, and how living and extinct things have come to be the way they are.^[1] The theory of evolution is a very important idea in biology. Theodosius Dobzhansky, a well-known evolutionary biologist, said: «Nothing in biology makes sense except in the light of evolution».^[2]

Evolution has been happening since life started on Earth and is happening now. Evolution is caused mostly by natural selection. Living things are not identical to each other. Even living things of the same species look, move, and behave differently to some extent. Some differences make it easier for living things to survive and reproduce. Differences may make it easier to find food, hide from danger, or give birth to offspring which survive. The offspring have some of the things which made it easier for their parents to have them. Over time, these differences continue, and living things change enough to become new species.

It is known that living things have changed over time, because their remains can be seen in the rocks. These remains are called ‘fossils’. This proves that the animals and plants of today are different from those of long ago. The older the fossils, the bigger the differences from modern forms.^[3] This has happened because evolution has taken place. That evolution has taken place is a fact, because it is overwhelmingly supported by many lines of evidence.^[4][5][6] At the same time, evolutionary questions are still being actively researched by biologists.

Comparison of DNA sequences allows organisms to be grouped by how similar their sequences are. In 2010 an analysis compared sequences to phylogenetic trees, and supported the idea of common descent. There is now «strong quantitative support, by a formal test»,^[7] for the unity of life.^[8]

Evidence[change | change source]

The evidence for evolution is given in a number of books.^{[9][10][11][12]} Some of this evidence is discussed here.

Fossils show that change has occurred[change | change source]

The realization that some rocks contain fossils was a very important event in natural history. There are three parts to this story:

1. The realization that things in rocks which looked organic actually were the altered remains of living things. This was settled in the 16th and 17th centuries by Conrad Gessner, Nicolaus Steno, Robert Hooke and others.^[13][14]

2. The realization that many fossils represented species which do not exist today. It was Georges Cuvier, the comparative anatomist, who proved that extinction occurred and that different strata contained different fossils.^[15]p108

3. The realization that early fossils were simpler organisms than later fossils. Also, the later the rocks, the more like the present day are the fossils.^[16]

«The most convincing evidence for the occurrence of evolution is the discovery of extinct organisms in older geological strata… The older the strata are…the more different the fossil will be from living representatives… that is to be expected if the fauna and flora of the earlier strata had gradually evolved into their descendants. Ernst Mayr ^[1]p13

Geographical distribution[change | change source]

Where species live is a topic which fascinated both Charles Darwin and Alfred Russel Wallace.^[17][18][19] When new species occur, usually by the splitting of older species, this takes place in one place in the world. Once it is established, a new species may spread to some places and not others.

Australasia[change | change source]

Australasia has been separated from other continents for many millions of years. In the main part of the continent, Australia, 83% of mammals, 89% of reptiles, 90% of fish and insects, and 93% of amphibians are endemic.^[20] Its native mammals are mostly marsupials like kangaroos, bandicoots, and quolls.^[21] By contrast, marsupials are today totally absent from Africa and form a small portion of the mammalian fauna of South America, where opossums, shrew opossums, and the monito del monte occur (see the Great American Interchange).

The only living representatives of primitive egg-laying mammals (monotremes) are the echidnas and the platypus. They are only found in Australasia, which includes Tasmania, New Guinea, and Kangaroo Island. These monotremes are totally absent in the rest of the world.^[22] On the other hand, Australia is missing many groups of placental mammals that are common on other continents (carnivora, artiodactyls, shrews, squirrels, lagomorphs), although it does have indigenous bats and rodents, which arrived later.^[23]

The evolutionary story is that placental mammals evolved in Eurasia, and wiped out the marsupials and monotremes wherever they spread. They did not reach Australasia until more recently. That is the simple reason why Australia has most of the world’s marsupials and all the world’s monotremes.

Evolution of horses[change | change source]

The evolution of the horse family (Equidae) is a good example of the way that evolution works. The oldest fossil of a horse is about 52 million years old. It was a small animal with five toes on the front feet and four on the hind feet. At that time, there were more forests in the world than today. This horse lived in woodland, eating leaves, nuts and fruit with its simple teeth. It was only about as big as a fox.^[24]

About 30 million years ago the world started to become cooler and drier. Forests shrank; grassland expanded, and horses changed. They ate grass, they grew larger, and they ran faster because they had to escape faster predators. Because grass wears teeth out, horses with longer-lasting teeth had an advantage.

For most of this long period of time, there were a number of horse types (genera). Now only one genus exists: the modern horse, Equus. It has teeth which grow all its life, hooves on single toes, great long legs for running, and the animal is big and strong enough to survive in the open plain.^[24] Horses lived in western Canada until 12,000 years ago,^[25] but all horses in North America became extinct about 11,000 years ago. The causes of this extinction are not yet clear. Climate change and over-hunting by humans are suggested.

So, scientists can see that changes have happened. They have happened slowly over a long time. How these changes have come about is explained by the theory of evolution.

Hawaiian Drosophila (fruit flies)[change | change source]

In about 6,500 sq mi (17,000 km²), the Hawaiian Islands have the most diverse collection of Drosophila flies in the world, living from rainforests to mountain meadows. About 800 Hawaiian fruit fly species are known.

Genetic evidence shows that all the native fruit fly species in Hawaiʻi have descended from a single ancestral species that came to the islands, about 20 million years ago. Later adaptive radiation was caused by a lack of competition and a wide variety of vacant niches. Although it would be possible for a single pregnant female to colonise an island, it is more likely to have been a group from the same species.^{[26][27][28][29]}

Distribution of Glossopteris[change | change source]

The combination of continental drift and evolution can explain what is found in the fossil record. Glossopteris is an extinct species of seed fern plants from the Permian period on the ancient supercontinent of Gondwana.^[30]

Glossopteris fossils are found in Permian strata in southeast South America, southeast Africa, all of Madagascar, northern India, all of Australia, all of New Zealand, and scattered on the southern and northern edges of Antarctica.

During the Permian, these continents were connected as Gondwana. This is known from magnetic striping in the rocks, other fossil distributions, and glacial scratches pointing away from the temperate climate of the South Pole during the Permian.^[11]p103

Common descent[change | change source]

When biologists look at living things, they see that animals and plants belong to groups which have something in common. Charles Darwin explained that this followed naturally if «we admit the common parentage of allied forms, together with their modification through variation and natural selection».^{[17]p402[9]p456}

For example, all insects are related. They share a basic body plan, whose development is controlled by master regulatory genes.^[31] They have six legs; they have hard parts on the outside of the body (an exoskeleton); they have eyes formed of many separate chambers, and so on. Biologists explain this with evolution. All insects are the descendants of a group of animals who lived a long time ago. They still keep the basic plan (six legs and so on) but the details change. They look different now because they changed in different ways: this is evolution.^[32]

It was Darwin who first suggested that all life on Earth had a single origin, and from that beginning «endless forms most beautiful and most wonderful have been, and are being, evolved».^[9]p490[17] Evidence from molecular biology in recent years has supported the idea that all life is related by common descent.^[33]

Vestigial structures[change | change source]

Strong evidence for common descent comes from vestigial structures.^[17]p397 The useless wings of flightless beetles are sealed under fused wing covers. This can be simply explained by their descent from ancestral beetles which had wings that worked.^[12]p49

Rudimentary body parts, those that are smaller and simpler in structure than corresponding parts in ancestral species, are called vestigial organs. Those organs are functional in the ancestral species but are now either nonfunctional or re-adapted to a new function. Examples are the pelvic girdles of whales, halteres (hind wings) of flies, wings of flightless birds, and the leaves of some xerophytes (e.g. cactus) and parasitic plants (e.g. dodder).

However, vestigial structures may have their original function replaced with another. For example, the halteres in flies help balance the insect while in flight, and the wings of ostriches are used in mating rituals and aggressive displays. The ear ossicles in mammals are former bones of the lower jaw.

«Rudimentary organs plainly declare their origin and meaning…» (p262). «Rudimentary organs… are the record of a former state of things, and have been retained solely through the powers of inheritance… far from being a difficulty, as they assuredly do on the old doctrine of creation, might even have been anticipated in accordance with the views here explained» (p402). Charles Darwin.^[17]

In 1893, Robert Wiedersheim published a book on human anatomy and its relevance to man’s evolutionary history. This book contained a list of 86 human organs that he considered vestigial.^[34] This list included examples such as the appendix and the 3rd molar teeth (wisdom teeth).

The strong grip of a baby is another example.^[35] It is a vestigial reflex, a remnant of the past when pre-human babies clung to their mothers’ hair as the mothers swung through the trees. Human babies’ feet curl up when they are sitting down, while primate babies can grip with their feet as well. All primates except modern man have thick body hair which an infant can grasp, unlike modern humans. The grasp reflex allows the mother to escape danger by climbing a tree using both hands and feet.^[11][36]

Vestigial organs often have some selection against them. The original organs take resources to build and maintain. If they no longer have a function, reducing their size improves fitness. There is direct evidence of selection. Some cave crustacea reproduce more successfully with smaller eyes than do those with larger eyes. This may be because the nervous tissue dealing with sight now becomes available to handle other sensory input.^[37]p310

Embryology[change | change source]

From the eighteenth century, it was known that embryos of different species were much more similar than the adults. In particular, some parts of embryos reflect their evolutionary past. For example, the embryos of land vertebrates develop gill slits like fish embryos. Of course, this is only a temporary stage, which gives rise to many structures in the neck of reptiles, birds, and mammals. The proto-gill slits are part of a complicated system of development: that is why they persisted.^[31]

Another example is the embryonic teeth of baleen whales.^[38] They are later lost. The baleen filter is developed from different tissue, called keratin. Early fossil baleen whales did actually have teeth as well as the baleen.^[39]

A good example is the barnacle. It took many centuries before natural historians discovered that barnacles were crustacea. Their adults look so unlike other crustacea, but their larvae are very similar to those of other crustacea.^[40]

Artificial selection[change | change source]

Charles Darwin lived in a world where animal husbandry and domesticated crops were vitally important. In both cases, farmers selected individuals for breeding that had desirable characteristics and prevented the breeding of individuals with less desirable characteristics. The eighteenth and early nineteenth centuries saw growth in scientific agriculture. Some of that growth was due to artificial breeding.

Darwin discussed artificial selection as a model for natural selection in the 1859 first edition of his work On the Origin of Species, in Chapter IV: Natural selection:

«Slow though the process of selection may be, if feeble man can do much by his powers of artificial selection, I can see no limit to the amount of change… which may be effected in the long course of time by nature’s power of selection».^[9]p109[41]

Nikolai Vavilov showed that rye, originally a weed, came to be a crop plant by unintentional selection. Rye is a tougher plant than wheat: it survives in harsher conditions. Having become a crop like wheat, rye was able to become a crop plant in harsh areas, such as hills and mountains.^[42][43]

There is no real difference in the genetic processes underlying artificial and natural selection, and the concept of artificial selection was used by Charles Darwin as an illustration of the wider process of natural selection. There are practical differences. Experimental studies of artificial selection show that «the rate of evolution in selection experiments is at least two orders of magnitude (that is 100 times) greater than any rate seen in nature or the fossil record».^[44]p157

Artificial new species[change | change source]

Some have thought that artificial selection could not produce new species. It now seems that it can.

New species have been created by domesticated animal husbandry, but the details are not known or not clear. For example, domestic sheep were created by hybridisation, and no longer produce viable offspring with Ovis orientalis, one species from which they are descended.^[45] Domestic cattle, on the other hand, can be considered the same species as several varieties of wild ox, gaur, yak, etc., as they readily produce fertile offspring with them.^[46]

The best-documented new species came from laboratory experiments in the late 1980s. William Rice and G.W. Salt bred fruit flies, Drosophila melanogaster, using a maze with three different choices of habitat such as light/dark and wet/dry. Each generation was put into the maze, and the groups of flies that came out of two of the eight exits were set apart to breed with each other in their respective groups.

After thirty-five generations, the two groups and their offspring were isolated reproductively because of their strong habitat preferences: they mated only within the areas they preferred, and so did not mate with flies that preferred the other areas.^[47][48]

Diane Dodd was also able to show how reproductive isolation can develop from mating preferences in Drosophila pseudoobscura fruit flies after only eight generations using different food types, starch, and maltose.^[49]

Dodd’s experiment has been easy for others to repeat. It has also been done with other fruit flies and foods.^[50]

Observable changes[change | change source]

Some biologists say that evolution has happened when a trait that is caused by genetics becomes more or less common in a group of organisms.^[51] Others call it evolution when new species appear.

Changes can happen quickly in smaller, simpler organisms. For example, many bacteria that cause disease can no longer be killed with some antibiotic medicines. These medicines have only been in use since the 1940s, and at first, they worked extremely well. The bacteria have evolved so that they are less affected by antibiotics.^[52] The drugs killed off all the bacteria except a few which had some resistance. These few resistant bacteria reproduced, and their offspring had the same drug resistance.

The Colorado beetle is famous for its ability to resist pesticides. Over the last 50 years it has become resistant to 52 chemical compounds used in insecticides, including cyanide.^[53] This is natural selection sped up by artificial conditions. However, not every population is resistant to every chemical.^[54] The populations only become resistant to chemicals used in their area.

History[change | change source]

Although there were a number of natural historians in the 18th century who had some idea of evolution, the first well-formed ideas came in the 19th century. Four biologists are considered the most important.

Lamarck[change | change source]

Jean-Baptiste de Lamarck (1744–1829), a French biologist, claimed that animals changed according to natural laws. He said that animals could pass on traits they had acquired during their lifetime to their offspring, using inheritance. Today, his theory is known as Lamarckism. Its main purpose is to explain adaptations by natural means.^[55] He proposed a tendency for organisms to become more complex, moving up a ladder of progress, plus use and disuse.

Lamarck’s idea was that a giraffe’s neck grew longer because it tried to reach higher up. This idea failed because it conflicts with heredity (Mendel’s work). Mendel made his discoveries about half a century after Lamarck’s work.

Darwin[change | change source]

Charles Darwin (1809–1882) wrote his On the Origin of Species in 1859. In this book, he put forward much evidence that evolution had occurred. He also proposed natural selection as the way evolution had taken place. But Darwin did not understand genetics and how traits were actually passed on. He could not accurately explain what made children look like their parents.

Nevertheless, Darwin’s explanation of evolution was fundamentally correct. In contrast to Lamarck, Darwin’s idea was that the giraffe’s neck became longer because those with longer necks survived better.^[17]p177/9 These survivors passed their genes on, and in time the whole species got longer necks.

Wallace[change | change source]

Alfred Russel Wallace OM FRS (1823–1913) was a British naturalist, explorer, biologist, and social activist. He proposed a theory of natural selection at about the same time as Darwin. His idea was published in 1858 together with Charles Darwin’s idea.

Mendel[change | change source]

An Austrian monk called Gregor Mendel (1822–1884) bred plants. In the mid-19th century, he discovered how traits were passed on from one generation to the next.

He used peas for his experiments: some peas have white flowers and others have red ones. Some peas have green seeds and others have yellow seeds. Mendel used artificial pollination to breed the peas. His results are discussed further in Mendelian inheritance. Darwin thought that the inheritance from both parents blended together. Mendel proved that the genes from the two parents stay separate, and may be passed on unchanged to later generations.

Mendel published his results in a journal that was not well-known, and his discoveries were overlooked. Around 1900, his work was rediscovered.^[56][57] Genes are bits of information made of DNA which work like a set of instructions. A set of genes are in every living cell. Together, genes organise the way an egg develops into an adult. With mammals, and many other living things, a copy of each gene comes from the father and another copy from the mother. Some living organisms, including some plants, only have one parent, so get all their genes from them. These genes produce the genetic differences that evolution acts on.

Darwin’s theory[change | change source]

Darwin’s On the Origin of Species has two themes: the evidence for evolution, and his ideas on how evolution took place. This section deals with the second issue.

Variation[change | change source]

The first two chapters of the Origin deal with variations in domesticated plants and animals, and variations in nature.

All living things show variation. Every population which has been studied shows that animals and plants vary as much as humans do.^[58][59]p90 This is a great fact of nature, and without it evolution would not occur. Darwin said that, just as man selects what he wants in his farm animals, so in nature the variations allow natural selection to work.^[60]

The features of an individual are influenced by two things, heredity and environment. First, development is controlled by genes inherited from the parents. Second, living brings its own influences. Some things are entirely inherited, others partly, and some not inherited at all.

The colour of eyes is entirely inherited; they are a genetic trait. Height or weight is only partly inherited, and language is not at all inherited. The fact that humans can speak is inherited, but what language is spoken depends on where a person lives and what they are taught. Another example: a person inherits a brain of somewhat variable capacity. What happens after birth depends on many things such as home environment, education, and other experiences. When a person is an adult, their brain is what their inheritance and life experience have made it.

Evolution only concerns the traits which can be inherited, wholly or partly. The hereditary traits are passed on from one generation to the next through genes. A person’s genes contain all the characteristics that they inherit from their parents. The accidents of life are not passed on. Each person lives a somewhat different life, which increases the differences.

Organisms in any population vary in reproductive success.^[61]p81 From the point of view of evolution, ‘reproductive success’ means the total number of offspring which live to breed and leave offspring themselves.

Inherited variation[change | change source]

Variation can only affect future generations if it is inherited. Because of the work of Gregor Mendel, we know that much variation is inherited. Mendel’s ‘factors’ are now called genes. Research has shown that almost every individual in a sexually reproducing species is genetically unique.^[62]p204

Genetic variation is increased by gene mutations. DNA does not always reproduce exactly. Rare changes occur, and these changes can be inherited. Many changes in DNA cause faults; some are neutral or even advantageous. This gives rise to genetic variation, which is the seed corn of evolution. Sexual reproduction, by the crossing over of chromosomes during meiosis, spreads variation through the population. Other events, like natural selection and drift, reduce variation. A population in the wild always has variation, but the details are always changing.^[59]p90

Natural selection[change | change source]

Evolution mainly works by natural selection. What does this mean? Animals and plants which are best suited to their environment will, on average, survive better. There is a struggle for existence. Those who survive will reproduce and create the next generation. Their genes will be passed on, and the genes of those who did not reproduce will not. This is the basic mechanism which changes the characteristics of a population and causes evolution.

Natural selection explains why living organisms change over time, and explains the anatomy, functions, and behavior that they have. It works like this:

1. All living things have such fertility that their population size could increase rapidly forever.
2. However, population sizes do not increase forever. Mostly, population sizes remain about the same.
3. Food and other resources are limited. Therefore, there is competition for food and resources.
4. No two individuals are alike. Therefore, they will not have the same chances to live and reproduce.
5. Much of this variation can be inherited. Parents pass traits to their children through their genes.
6. The next generation can only come from those that survive and reproduce. After many generations of this, the population will have more helpful genetic differences, and fewer harmful ones.^[63] Natural selection is really a process of elimination.^[1]p117 The elimination is being caused by the relative fit between individuals and the environment they live in.

Selection in natural populations[change | change source]

There are now many cases where natural selection has been proved to occur in wild populations.^[4][64][65] Almost every case investigated of camouflage, mimicry and polymorphism has shown strong effects of selection.^[66]

The force of selection can be much stronger than was thought by the early population geneticists. The resistance to pesticides has grown quickly. Resistance to warfarin in Norway rats (Rattus norvegicus) grew rapidly because those that survived made up more and more of the population. Research showed that, in the absence of warfarin, the resistant homozygote was at a 54% disadvantage to the normal wild type homozygote.^[59]p182[67] This great disadvantage was quickly overcome by the selection for warfarin resistance.

Mammals normally cannot drink milk as adults, but humans are an exception. Milk is digested by the enzyme lactase, which switches off as mammals stop taking milk from their mothers. The human ability to drink milk during adult life is supported by a lactase mutation which prevents this switch-off. Human populations have a high proportion of this mutation wherever milk is important in the diet. The spread of this ‘milk tolerance’ is promoted by natural selection, because it helps people survive where milk is available. Genetic studies suggest that the oldest mutations causing lactase persistence only reached high levels in human populations in the last ten thousand years.^[68][69] Therefore, lactase persistence is often cited as an example of recent human evolution.^[70][71] As lactase persistence is genetic, but animal husbandry a cultural trait, this is gene–culture coevolution.^[72]

Adaptation[change | change source]

Adaptation is one of the basic phenomena of biology.^[73] Through the process of adaptation, an organism becomes better suited to its habitat.^[74]

Adaptation is one of the two main processes that explain the diverse species we see in biology. The other is speciation (species-splitting or cladogenesis).^[75][76] A favourite example used today to study the interplay of adaptation and speciation is the evolution of cichlid fish in African rivers and lakes.^[77][78]

When people speak about adaptation they often mean something which helps an animal or plant survive. One of the most widespread adaptations in animals is the evolution of the eye. Another example is the adaptation of horses’ teeth to grinding grass. Camouflage is another adaptation; so is mimicry. The better-adapted animals are the most likely to survive and reproduce successfully (natural selection).

An internal parasite (such as a fluke) is a good example: it has a very simple bodily structure, but still the organism is highly adapted to its particular environment. From this we see that adaptation is not just a matter of visible traits: in such parasites, critical adaptations take place in the life cycle, which is often quite complex.^[79]

Limitations[change | change source]

Not all features of an organism are adaptations.^[59]p251 Adaptations tend to reflect the past life of a species. If a species has recently changed its life style, a once valuable adaptation may become useless, and eventually become a dwindling vestige.

Adaptations are never perfect. There are always tradeoffs between the various functions and structures in a body. It is the organism as a whole that lives and reproduces, therefore it is the complete set of adaptations that is passed on to future generations.

Genetic drift and its effect[change | change source]

In populations, there are forces that add variation to the population (such as mutation), and forces that remove it. Genetic drift is the name given to random changes which remove variation from a population. Genetic drift gets rid of variation at the rate of 1/(2N) where N = population size.^[44]p29 It is therefore «a very weak evolutionary force in large populations».^[44]p55

Genetic drift explains how random chance can affect evolution in surprisingly big ways, but only when populations are quite small. Overall, its action is to make the individuals more similar to each other, and hence more vulnerable to disease or to chance events in their environment.

1. Drift reduces genetic variation in populations, potentially reducing a population’s ability to survive new selective pressures.
2. Genetic drift acts faster and has more drastic results in smaller populations. Small populations usually become extinct.
3. Genetic drift may contribute to speciation (starting a new species) if the small group does survive.
4. Bottleneck events: when a large population is suddenly and drastically reduced in size by some event, the genetic variety will be very much reduced. Infections and extreme climate events are frequent causes. Occasionally, invasions by more competitive species can be devastating.^[80]
   ♦ In late 1800s, hunting reduced the Northern elephant seal to only about 20 individuals. Although the population has rebounded, its genetic variability is much less than that of the Southern elephant seal.
   ♦ Cheetahs have very little variation. We think the species was reduced to a small number at some recent time. Because it lacks genetic variation, it is in danger of infectious diseases.^[81]
5. Founder events: these occur when a small group buds off from a larger population. The small group then lives separately from the main population. The human species is often quoted as having been through such stages. For example, when groups left Africa to set up elsewhere (see human evolution). Apparently, we have less variation than would be expected from our worldwide distribution.
   Groups that arrive on islands far from the mainland are also good examples. These groups, by virtue of their small size, cannot carry the full range of alleles to be found in the parent population.^[82][83]

Species[change | change source]

How species form is a major part of evolutionary biology. Darwin interpreted ‘evolution’ (a word he did not use at first) as being about speciation. That is why he called his famous book On the Origin of Species.

Darwin thought most species arose directly from pre-existing species. This is called anagenesis: new species by older species changing. Now we think most species arise by previous species splitting: cladogenesis.^[84][85]

Species splitting[change | change source]

Two groups that start the same can become very different if they live in different places. When a species gets split into two geographical regions, a process starts. Each adapts to its own situation. After a while, individuals from one group can no longer reproduce with the other group. Two separate species have evolved from one.

A German explorer, Moritz Wagner, during his three years in Algeria in the 1830s, studied flightless beetles. Each species is confined to a stretch of the north coast between rivers which descend from the Atlas mountains to the Mediterranean. As soon as one crosses a river, a different but closely related species appears.^[86] He wrote later:

«… a [new] species will only [arise] when a few individuals [cross] the limiting borders of their range… the formation of a new race will never succeed… without a long continued separation of the colonists from the other members of their species».^[87]

This was an early account of the importance of geographical separation. Another biologist who thought geographical separation was critical was Ernst Mayr.^[88]

One example of natural speciation is the three-spined stickleback, a sea fish that, after the last ice age, invaded freshwater, and set up colonies in isolated lakes and streams. Over about 10,000 generations, the sticklebacks show great differences, including variations in fins, changes in the number or size of their bony plates, variable jaw structure, and colour differences.^[89]

The wombats of Australia fall into two main groups, common wombats and hairy-nosed wombats. The two types look very similar, apart from the hairiness of their noses. However, they are adapted to different environments. Common wombats live in forested areas and eat mostly green food with lots of moisture. They often feed in the daytime. Hairy-nosed wombats live on hot dry plains where they eat dry grass with very little water or nutrition in it. Their metabolic rate is slow and they sleep most of the day underground.

When two groups that started the same become different enough, then they become two different species. Part of the theory of evolution is that all living things started the same, but then split into different groups over billions of years.^[90]

Modern evolutionary synthesis[change | change source]

This was an important movement in evolutionary biology, which started in the 1930s and finished in the 1950s.^[91][92] It has been updated regularly ever since.
The synthesis explains how the ideas of Charles Darwin fit with the discoveries of Gregor Mendel, who found out how we inherit our genes. The modern synthesis brought Darwin’s idea up to date. It bridged the gap between different types of biologists: geneticists, naturalists, and palaeontologists.

When the theory of evolution was developed, it was not clear that natural selection and genetics worked together. But Ronald Fisher showed that natural selection would work to change species.^[93] Sewall Wright explained genetic drift in 1931.^[94]

• Evolution and genetics: evolution can be explained by what we know about genetics, and what we see of animals and plants living in the wild.^[91][92]
• Thinking in terms of populations, rather than individuals, is important. The genetic variety existing in natural populations is a key factor in evolution.^[95]
• Evolution and fossils: the same factors which act today also acted in the past.^[96]
• Gradualism: evolution is gradual, and usually takes place by small steps. There are some exceptions to this, notably polyploidy, especially in plants.^[97][98]
• Natural selection: the struggle for existence of animals and plants in the wild causes natural selection. The strength of natural selection in the wild was greater than even Darwin expected.^[65]
• Genetic drift can be important in small populations.^[44]
• The rate of evolution can vary. There is very good evidence from fossils that different groups can evolve at different rates, and that different parts of an animal can evolve at different rates.^{[59]p292, 397}

Some areas of research[change | change source]

Co-evolution[change | change source]

Co-evolution is where the existence of one species is tightly bound up with the life of one or more other species.

New or ‘improved’ adaptations which occur in one species are often followed by the appearance and spread of related features in the other species. The life and death of living things is intimately connected, not just with the physical environment, but with the life of other species.

These relationships may continue for millions of years, as it has in the pollination of flowering plants by insects.^[99][100] The gut contents, wing structures, and mouthparts of fossilized beetles and flies suggest that they acted as early pollinators. The association between beetles and angiosperms during the Lower Cretaceous period led to parallel radiations of angiosperms and insects into the late Cretaceous. The evolution of nectaries in Upper Cretaceous flowers signals the beginning of the mutualism between hymenoptera and angiosperms.^[101]

Tree of life[change | change source]

Charles Darwin was the first to use this metaphor in biology. The evolutionary tree shows the relationships among various biological groups. It includes data from DNA, RNA and protein analysis. Tree of life work is a product of traditional comparative anatomy, and modern molecular evolution and molecular clock research.

The major figure in this work is Carl Woese, who defined the Archaea, the third domain (or kingdom) of life.^[102] Below is a simplified version of present-day understanding.^[103]

Macroevolution[change | change source]

Macroevolution: the study of changes above the species level, and how they take place. The basic data for such a study are fossils (palaeontology) and the reconstruction of ancient environments. Some subjects whose study falls within the realm of macroevolution:

• Adaptive radiation, such as the Cambrian Explosion.
• Changes in biodiversity through time.
• Mass extinctions.
• Speciation and extinction rates.
• The debate between punctuated equilibrium and gradualism.
• The role of development in shaping evolution: heterochrony; hox genes.
• Origin of major categories: cleidoic egg; origin of birds.

It is a term of convenience: for most biologists it does not suggest any change in the process of evolution.^{[4][104][105]p87} For some palaeontologists, what they see in the fossil record cannot be explained just by the gradualist evolutionary synthesis.^[106] They are in the minority.

Altruism and group selection[change | change source]

Altruism – the willingness of some to sacrifice themselves for others – is widespread in social animals. As explained above, the next generation can only come from those who survive and reproduce. Some biologists have thought that this meant altruism could not evolve by the normal process of selection. Instead a process called «group selection» was proposed.^[107][108] Group selection refers to the idea that alleles can become fixed or spread in a population because of the benefits they bestow on groups, regardless of the alleles’ effect on the fitness of individuals within that group.

For several decades, critiques cast serious doubt on group selection as a major mechanism of evolution.^{[109][110][111][112]}

In simple cases it can be seen at once that traditional selection suffices. For example, if one sibling sacrifices itself for three siblings, the genetic disposition for the act will be increased. This is because siblings share on average 50% of their genetic inheritance, and the sacrificial act has led to greater representation of the genes in the next generation.

Altruism is now generally seen as emerging from standard selection.^{[113][114][115][116][117]} The warning note from Ernst Mayr, and the work of William Hamilton are both important to this discussion.^[118][119]

Hamilton’s equation[change | change source]

Hamilton’s equation describes whether or not a gene for altruistic behaviour will spread in a population. The gene will spread if rxb is greater than c:

where:

Sexual reproduction[change | change source]

Main article: Sex

At first, sexual reproduction might seem to be at a disadvantage compared with asexual reproduction. In order to be advantageous, sexual reproduction (cross-fertilisation) has to overcome a two-fold disadvantage (takes two to reproduce) plus the difficulty of finding a mate. Why, then, is sex so nearly universal among eukaryotes? This is one of the oldest questions in biology.^[120]

The answer has been given since Darwin’s time: because the sexual populations adapt better to changing circumstances. A recent laboratory experiment suggests this is indeed the correct explanation.^[121][122]

«When populations are outcrossed^[123] genetic recombination occurs between different parental genomes. This allows beneficial mutations to escape deleterious alleles on its original background, and to combine with other beneficial alleles that arise elsewhere in the population. In selfing^[124] populations, individuals are largely homozygous and recombination has no effect».^[121]

In the main experiment, nematode worms were divided into two groups. One group was entirely outcrossing, the other was entirely selfing. The groups were subjected to a rugged terrain and repeatedly subjected to a mutagen.^[125] After 50 generations, the selfing population showed a substantial decline in fitness (= survival), whereas the outcrossing population showed no decline. This is one of a number of studies that show sexuality to have real advantages over non-sexual types of reproduction.^[126]

What evolution is used for today[change | change source]

An important activity is artificial selection for domestication. This is when people choose which animals to breed from, based on their traits. Humans have used this for thousands of years to domesticate plants and animals.^[127]

More recently, it has become possible to use genetic engineering. New techniques such as ‘gene targeting’ are now available. The purpose of this is to insert new genes or knock out old genes from the genome of a plant or animal. A number of Nobel Prizes have already been awarded for this work.

However, the real purpose of studying evolution is to explain and help our understanding of biology. After all, it is the first good explanation of how living things came to be the way they are. That is a big achievement. The practical things come mostly from genetics, the science started by Gregor Mendel, and from molecular and cell biology.

Evolution gems[change | change source]

In 2010 the journal Nature selected 15 topics as ‘Evolution gems’. These were:

Gems from the fossil record[change | change source]

1. Land-living ancestors of whales
2. From water to land (see tetrapod)
3. The origin of feathers (see origin of birds)
4. The evolutionary history of teeth
5. The origin of vertebrate skeleton

Gems from habitats[change | change source]

1. Natural selection in speciation
2. Natural selection in lizards
3. A case of co-adaptation
4. Differential dispersal in wild birds
5. Selective survival in wild guppies
6. Evolutionary history matters

Gems from molecular processes[change | change source]

1. Darwin’s Galapagos finches
2. Microevolution meets macroevolution
3. Toxin resistance in snakes and clams
4. Variation versus stability

• Nature is the oldest scientific weekly journal. The link downloads as a free text file, complete with references. The idea is to make the information available to teachers.^[128]

Responses to the idea of evolution[change | change source]

Debates about the fact of evolution[change | change source]

The idea that all life evolved had been proposed before Charles Darwin published On the Origin of species. Even today, some people still discuss the concept of evolution and what it means to them, their philosophy, and their religion. Evolution does explain some things about our human nature.^[130] People also talk about the social implications of evolution, for example in sociobiology.

Some people have the religious belief that life on Earth was created by a god. In order to fit in the idea of evolution with that belief, people have used ideas like guided evolution or theistic evolution. They say that evolution is real, but is being guided in some way.^{[15][131][132][133]}

There are many different concepts of theistic evolution. Many creationists believe that the creation myth found in their religion goes against the idea of evolution.^[134] As Darwin realised, the most controversial part of the evolutionary thought is what it means for human origins.

In some countries, especially in the United States, there is tension between people who accept the idea of evolution and those who do not accept it. The debate is mostly about whether evolution should be taught in schools, and in what way this should be done.^[135]

Other fields, like cosmology^[136] and earth science^[137] also do not match with the original writings of many religious texts. These ideas were once also fiercely opposed. Death for heresy was threatened to those who wrote against the idea that Earth was the center of the universe.

Evolutionary biology is a more recent idea. Certain religious groups oppose the idea of evolution more than other religious groups do. For instance, the Roman Catholic Church now has the following position on evolution: Pope Pius XII said in his encyclical Humani Generis published in the 1950s:

«The Church does not forbid that (…) research and discussions (..) take place with regard to the doctrine of evolution, in as far as it inquires into the origin of the human body as coming from pre-existent and living matter,» Pope Pius XII Humani Generis^[138]

Pope John Paul II updated this position in 1996. He said that Evolution was «more than a hypothesis»:

«In his encyclical Humani Generis, my predecessor Pius XII has already [said] that there is no conflict between evolution and the doctrine of the faith regarding man and his vocation. (…) Today, more than a half-century after (..) that encyclical, some new findings lead us toward the recognition of evolution as more than an hypothesis. In fact it is remarkable that this theory has had progressively greater influence on the spirit of researchers, following a series of discoveries in different scholarly disciplines,» Pope John Paul II speaking to the Pontifical Academy of Science^[139]

The Anglican Communion also does not oppose the scientific account of evolution.

Using evolution for other purposes[change | change source]

Many of those who accepted evolution were not much interested in biology. They were interested in using the theory to support their own ideas on society.

Racism[change | change source]

Some people have tried to use evolution to support racism. People wanting to justify racism claimed that certain groups, such as black people, were inferior. In nature, some animals do survive better than others, and it does lead to animals better adapted to their circumstances. With humans groups from different parts of the world, all evolution can say is that each group is probably well suited to its original situation. Evolution makes no judgements about better or worse. It does not say that any human group is superior to any other.^[140]

Eugenics[change | change source]

The idea of eugenics was rather different. Two things had been noticed as far back as the 18th century. One was the great success of farmers in breeding cattle and crop plants. They did this by selecting which animals or plants would produce the next generation (artificial selection). The other observation was that lower class people had more children than upper-class people. If (and it’s a big if) the higher classes were there on merit, then their lack of children was the exact reverse of what should be happening. Faster breeding in the lower classes would lead to the society getting worse.

The idea to improve the human species by selective breeding is called eugenics. The name was proposed by Francis Galton, a bright scientist who meant to do good.^[141] He said that the human stock (gene pool) should be improved by selective breeding policies. This would mean that those who were considered «good stock» would receive a reward if they reproduced. However, other people suggested that those considered «bad stock» would need to undergo compulsory sterilization, prenatal testing and birth control. The German Nazi government (1933–1945) used eugenics as a cover for their extreme racial policies, with dreadful results.^[142]

The problem with Galton’s idea is how to decide which features to select. There are so many different skills people could have, you could not agree who was «good stock» and who was «bad stock». There was rather more agreement on who should not be breeding. Several countries passed laws for the compulsory sterilisation of unwelcome groups.^[143] Most of these laws were passed between 1900 and 1940. After World War II, disgust at what the Nazis had done squashed any more attempts at eugenics.

Algorithm design[change | change source]

Some equations can be solved using algorithms that simulate evolution. Evolutionary algorithms work like that.

[change | change source]

Another example of using ideas about evolution to support social action is social Darwinism. Social Darwinism is a term given to the ideas of the 19th century social philosopher Herbert Spencer. Spencer believed the survival of the fittest could and should be applied to commerce and human societies as a whole.

Again, some people used these ideas to claim that racism, and ruthless economic policies were justified.^[144] Today, most biologists and philosophers say that the theory of evolution should not be applied to social policy.^[145][146]

Controversy[change | change source]

Some people disagree with the idea of evolution. They disagree with it for a number of reasons. Most often these reasons are influenced by or based on their religious beliefs instead of science. People who do not agree with evolution usually believe in creationism or intelligent design.

Despite this, evolution is one of the most successful theories in science. People have discovered it to be useful for different kinds of research. None of the other suggestions explain things, such as fossil records, as well. So, for almost all scientists, evolution is not in doubt.^{[2][147][148][149]}

Further reading[change | change source]

Evidence for evolution[change | change source]

These books are mostly about the evidence for evolution.

• Coyne, Jerry A. 2009 Why evolution is true. Oxford University Press, Oxford. ISBN 0670-02053-2 (pbk)
• Dawkins, Richard 2009. The greatest show on Earth. Bantam, London. ISBN 978-0-593-06173-2 (hbk)
• Futuyma D.J. 1983. Science on trial: the case for evolution. Pantheon Books, New York. ISBN 0-394-52371-7; 2nd ed 1995 Sinauer Associates, Sunderland, Massachusetts. ISBN 0-87893-184-8.
• Prothero, Donald R. 2007. Evolution: what the fossils say and why it matters. Columbia University Press, New York. ISBN 978-0-231-13962-5 (hbk)

The process of evolution[change | change source]

These books cover most evolutionary topics.

• Barton N.H; Briggs D.E.G; Eisen J.A; Goldstein D.B. & Patel N.H. 2007. Evolution. New York: Cold Spring Harbor Laboratory Press. ISBN 978-0-879-69684-9. Strong in molecular evolution; brings together molecular biology with evolutionary concepts.
• Futuyma D.J. 1979. Evolutionary biology. 1st ed. Sinauer Associates, Sunderland, Massachusetts. ISBN 0-87893-199-6; 2nd ed 1986 Sinauer. ISBN 0-87893-188-0; 3rd ed 1998 Sinauer. ISBN 0-87893-189-9. Widely used textbook, available second-hand. For students and teachers.
• Futuyma D.J. 2005. Evolution. Sinauer Associates, Sunderland, Massachusetts. ISBN 0-87893-187-2; 2nd ed 2009 Sinauer. ISBN 978-0-87893-223-8. Successor to above; but basically a different book. For students and teachers.
• Freeman, Scott & Herron, Jon; 1997. Evolutionary analysis. Prentice Hall ISBN 0-13-568023-9; 2nd ed 2000 ISBN 0-13-017291-X; 3rd ed 2004 Cummings ISBN 978-0-13-101859-4; 4th ed 2007 Cummings ISBN 0-13-227584-8. Modern topics such as phylogenetic trees based on genomics, genetics, molecular biology. Has website: [4] Archived 2012-12-15 at the Wayback Machine For students and teachers.
• Ridley, Mark 1993. Evolution. Blackwell ISBN 0-86542-226-5; 2nd ed 1996 Wiley-Blackwell ISBN 0-86542-495-0; 3rd ed 2003 Wiley ISBN 978-1-4051-0345-9. Comprehensive: case studies, commentary, dedicated website and CD. For students and teachers.
• Mayr, Ernst. 2001. What evolution is. Weidenfeld & Nicolson, London. ISBN 0-297-60741-3. Clearly written, for a general audience.

[change | change source]

• Evolutionary biology
• Coevolution
• Human evolution
• Adaptation
• Natural selection
• Sociobiology

References[change | change source]

Other websites[change | change source]

• Video (1980; Cosmos animation; 8:01): «Evolution» – Carl Sagan at YouTube
• Understanding Evolution — a guide prepared by the University of California, Berkeley
• Darwin Online Darwin’s publications; papers and bibliography; biographies and reviews.
• Talk Origins in depth website on information about evolution and the evidence for it
• National Center for Science Education Information on how evolution works
• Article about evolution — PBS

English[edit]

Wikiversity

Etymology[edit]

Borrowed from Latin ēvolūtiō, ēvolūtiōnis (“the act of unrolling, unfolding or opening (of a book)”), from ēvolūtus, perfect passive participle of ēvolvō (“unroll, unfold”), from ex + volvō (“roll”).

Pronunciation[edit]

• (Received Pronunciation) IPA^(key): /ˌiːvəˈluːʃ(ə)n/, /ɛvəˈluːʃ(ə)n/
• (General American) enPR: ĕv’ə-lo͞oʹshən, ēv’ə-, -lo͞oshʹn, IPA^(key): /ˌɛvəˈluʃ(ə)n/, /ˌivə-/
• Rhymes: -uːʃən
• Hyphenation: evo‧lu‧tion

Noun[edit]

evolution (countable and uncountable, plural evolutions)

1. A change of position.
   1. (military) A manoeuvre of troops or ships. [from 17th c.]

      • 1751, [Tobias] Smollett, chapter 106, in The Adventures of Peregrine Pickle […], volume IV, London: Harrison and Co., […], published 1781, →OCLC:

        Mean while, he never failed to be present, when any regiment, or corps of men, were drawn out to be exercised and reviewed, and accompanied them in all their evolutions […] .

      • 1779, Frances Burney, Journals & Letters, Penguin 2001, p. 117:

        Major Holroyd, who acted as the General, was extremely polite, and attentive, and came to us between every evolution, to explain and talk over the manoeuvres.

   2. (chiefly dance, sports) A turning movement, especially of the body. [from 17th c.]

      • 1751, [Tobias] Smollett, chapter 91, in The Adventures of Peregrine Pickle […], volume III, London: Harrison and Co., […], published 1781, →OCLC:

        Our necromancer […] taking up his wand, waved it around his head in a very mysterious motion, with a view of intimidating these forward visitants, who, far from being awed by this sort of evolution, became more and more obstreperous […] .

      • 1869, Anon., Miss Langley’s Will:

        It was a critical instant: the pirouette — it would fail, she feared. … the rapid whirl achieved in exact time, the whole evolution executed to perfection.

      • 1825, Theodore Edward Hook, Sayings and Doings: Passion and principle:

        … as he beheld the tenfold pirouette of a lovely girl, which presented to the public eye the whole of her form and figure; … to praise the dexterity and ease with which the unfortunate and degraded creature had performed the ungraceful evolution, the only merit of which, is the gross exposition of person, at which modesty shudders […]

      • 1863, Knightley Willia Horlock, The master of the hounds:

        «Look now, that pirouette — my stars! how Beauchamp would stare to see his darling perform such an evolution!»

      • 1869, William Clarke, The boy’s own book:

        By this operation each foot will describe an arc or segment of a circle. … This evolution is performed sometimes on one foot, sometimes on the other …

   3. (obsolete) A turned or twisted shape; an involution, a complex or intricate shape. [18th c.]
      • 1791, James Boswell, Life of Samuel Johnson, Oxford 2008, p. 298:

        ‘It is not in the showy evolutions of buildings, but in the multiplicity of human habitations which are crouded together, that the wonderful immensity of London consists.’

2. An unfolding.
   1. (now rare) The act or process of unfolding or opening out; the progression of events in regular succession. [from 17th c.]
   2. (geometry) The opening out of a curve; now more generally, the gradual transformation of a curve by a change of the conditions generating it. [from 17th c.]
   3. (mathematics, now chiefly historical) The extraction of a root from a given power. [from 17th c.]
   4. (chemistry) The act or an instance of giving off gas; emission. [from 18th c.]
3. Process of development.
   1. Development; the act or result of developing what was implicit in an idea, argument etc. [from 17th c.]

      The ongoing evolution of Lolita subculture fashion includes, among other things, the ballet style.

      • 2005, Eckhart Tolle, A New Earth:

        Suffering has a noble purpose: the evolution of consciousness and the burning up of the ego.

   2. A process of gradual change in a given system, subject, product etc., especially from simpler to more complex forms. [from 18th c.]

      Among other forms of change, the evolution of transportation has involved modification, diversification, convergence, divergence, hybridization, differentiation, and naturally, selection.

      • 1922, Ben Travers, chapter 4, in A Cuckoo in the Nest‎^[1]:

        By some paradoxical evolution rancour and intolerance have been established in the vanguard of primitive Christianity. Mrs. Spoker, in common with many of the stricter disciples of righteousness, was as inclement in demeanour as she was cadaverous in aspect.

      • 1976, Richard Dawkins, The Selfish Gene:

        There are some examples of cultural evolution in birds and monkeys, but […] it is our own species that really shows what cultural evolution can do.

   3. (biology) The transformation of animals, plants and other living things into different forms (now understood as a change in genetic composition) by the accumulation of changes over successive generations. [from 19th c.]

      • 1832, Charles Lyell, chapter I, in Principles of Geology […] , volume II, London: John Murray, page 11:

        […] and thus he [Lamarck] was inclined to assert the priority of the types of marine animals to those of the terrestrial, and to fancy, for example, that the testacea of the ocean existed first, until some of them, by gradual evolution, were improved into those inhabiting the land.

      • 1976, Richard Dawkins, The Selfish Gene:

        [Some books have] made the erroneous assumption that the important thing in evolution is the good of the species (or the group) rather than the good of the individual (or the gene).

Antonyms[edit]

• (accumulation of change): stagnation
• (gradual process): revolution
• (survival through adaptation): extinction

Derived terms[edit]

[edit]

Translations[edit]

See also[edit]

• Darwinism
• neo-Darwinism

References[edit]

• evolution at OneLook Dictionary Search
• evolution in Keywords for Today: A 21st Century Vocabulary, edited by The Keywords Project, Colin MacCabe, Holly Yanacek, 2018.
• «evolution» in Raymond Williams, Keywords (revised), 1983, Fontana Press, page 120.
• “evolution”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.
• evolution in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913

Swedish[edit]

Noun[edit]

evolution c

1. evolution; development
2. (biology) evolution

Declension[edit]

Declension of evolution
	Singular	Plural
Indefinite	Definite	Indefinite	Definite
Nominative	evolution	evolutionen	evolutioner	evolutionerna
Genitive	evolutions	evolutionens	evolutioners	evolutionernas

Derived terms[edit]

• evolutionär

See also[edit]

• utveckling

ev·o·lu·tion

 (ĕv′ə-lo͞o′shən, ē′və-)

n.

1.

a. A gradual process in which something changes into a different and usually more complex or better form.

b. A result of this process; a development: Judo is an evolution of an earlier martial art.

2. Biology

a. Change in the genetic composition of a population during successive generations, often resulting in the development of new species. The mechanisms of evolution include natural selection acting on the genetic variation among individuals, mutation, migration, and genetic drift.

b. The historical development of a related group of organisms; phylogeny.

3. Astronomy Change in the structure, chemical composition, or dynamical properties of a celestial object or system such as a planetary system, star, or galaxy. Evolution often changes the observable or measurable characteristics of the object or system.

4. A movement that is part of a set of ordered movements: naval evolutions in preparation for battle.

5. Mathematics The extraction of a root of a quantity.

---

[Latin ēvolūtiō, ēvolūtiōn-, from ēvolūtus, past participle of ēvolvere, to unroll; see evolve.]

---

ev′o·lu′tion·al, ev′o·lu′tion·ar′y (-shə-nĕr′ē) adj.

ev′o·lu′tion·ar′i·ly adv.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

evolution

(ˌiːvəˈluːʃən)

n

1. (Biology) biology a gradual change in the characteristics of a population of animals or plants over successive generations: accounts for the origin of existing species from ancestors unlike them. See also natural selection

2. a gradual development, esp to a more complex form: the evolution of modern art.

3. (Chemistry) the act of throwing off, as heat, gas, vapour, etc

4. a pattern formed by a series of movements or something similar

5. (Mathematics) an algebraic operation in which the root of a number, expression, etc, is extracted. Compare involution⁶

6. (Military) military an exercise carried out in accordance with a set procedure or plan

[C17: from Latin ēvolūtiō an unrolling, from ēvolvere to evolve]

ˌevoˈlutionary, ˌevoˈlutional adj

Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

ev•o•lu•tion

(ˌɛv əˈlu ʃən; esp. Brit. ˌi və-)

n.

1. any process of formation or growth; development: the evolution of the drama.

2. a product of development; something evolved.

3. Biol.

a. change in the gene pool of a population from generation to generation by such processes as mutation, natural selection, and genetic drift.

b. the development of a species or other group of organisms; phylogeny.

c. the theory that all existing organisms developed from earlier forms by natural selection; Darwinism.

4. a process of gradual, progressive change and development, as in a social or economic structure.

5. a motion incomplete in itself, but combining with coordinated motions to produce a single action, as in a machine.

6. a pattern formed by a series of movements: the evolutions of a figure skater.

7. Math. the extraction of a root from a quantity.

8. a military training exercise.

9. a movement executed by troops in formation.

ev`o•lu′tion•al, ev•o•lu′tion•ar′y, adj.

ev`o•lu′tion•al•ly, ev`o•lu`tion•ar′i•ly, adv.

Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.

ev·o·lu·tion

(ĕv′ə-lo͞o′shən)

The process by which species of organisms arise from earlier life forms and undergo change over a long period of time through natural selection. The genetic makeup of populations of organisms can be traced using fossils and recent advances in DNA technology to determine the relationships between members of a given species. See also natural selection. See Note at Darwin.

Did You Know? Darwin’s theory of evolution by natural selection assumed that tiny adaptations occur in organisms constantly over exceptionally long periods of time. Gradually, a new species develops that is distinct from its ancestors. In the 1970s, however, biologists Niles Eldredge and Stephen Jay Gould proposed that evolution by natural selection was a far more bumpy road. Based on types of fossils that exist around the world, they said that evolution is better described through punctuated equilibrium. That is, for long periods of time, species in fact remain virtually unchanged, not even gradually adapting. They are in equilibrium, in a balance with the environment. But when confronted with environmental challenges—sudden climate change, for example—organisms adapt quite quickly, perhaps in only a few thousand years. These active periods are punctuations, after which a new equilibrium exists and species remain stable until the next punctuation.

The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Evolution

the theory of evolution by natural selection of those species best adapted to survive the struggle for existence. — Darwinian, n., ad).

a principle or theory of evolution. — evolutionist, n., adj.

the theory of organic evolution advanced by the French naturalist Lamarck that characteristics acquired by habit, diseases, or adaptations to change in environment may be inherited. — Lamarckian, n., adj.

the theory that maintains natural selection to be the major factor in plant and animal evolution and denies the possibility of inheriting acquired characteristics. — Neo-Darwinist, n., adj. — Neo-Darwinian, n., adj.

a modern theory based on Lamarckism that states that acquired characteristics are inherited. — Neo-Lamarckian, n., adj.

progressive evolution, leading to the development of a new form, as can be seen through successive generations. See also society. — orthogenetic, adj.

the theory advanced by Darwin, now rejected, that each part of the body is represented in each cell by gemmules, which are the basic units of hereditary transmission. — pangenetic, adj.

the history of the development of a plant, animal, or racial type. — phylogenist, n. — phylogenetic, adj.

a devotion to the conditions which existed at the beginning of creation.

the ability of one species to change into another. — transformist, n.

1. the theory that chance is involved in evolution and that variation within a species is accidental.
2. the belief that chance rather than mere determinism operates in the cosmos. Cf. uniformitarianism.

1. Philosophy. a doctrine that the universe is governed only by rigid, unexceptionable law.
2. Geology. the concept that current geological processes explain all past geological occurrences. — uniformitarian, n., adj.

-Ologies & -Isms. Copyright 2008 The Gale Group, Inc. All rights reserved.

evolution

Change in the characteristics of a population of organisms over time.

Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited

1	0   0 The continuing process of change.

2

0   0 evolution Biologic evolution was contrasted with cultural (social) evolution in 1968 by A.G. Motulsky who pointed out that biologic evolution is mediated by genes, shows a slow rate of change, employs random variation (mutations) and selection as agents of change, new variants are often harmful, these new variants are transmitted from parents to offspring, t [..]

3	0   0 evolution [L. e-, out + volvere, to roll] All the changes that have transformed life on Earth from its earliest beginnings to the diversity that characterizes it today.

4	0   0 evolution 1(biology) the gradual development of plants, animals, etc. over many years as they adapt to changes in their environment the evolution of the human species Darwin’s theory of evolution2 the grad [..]

5	0   0 evolution 1620s, «an opening of what was rolled up,» from Latin evolutionem (nominative evolutio) «unrolling (of a book),» noun of action from past participle stem of evolvere «to unrol [..]

6	0   0 evolution process of how present types of organisms developed from earlier forms of life.

7

0   0 evolution Evolution is the process by which organisms change over time. Mutations produce genetic variation in populations, and the environment interacts with this variation to select those individuals best adapted to their surroundings. The best-adapted individuals leave behind more offspring than less well-adapted individuals. Given enough time, one specie [..]

8	0   0 evolution The long-term process through which a population of organisms accumulates genetic changes that enable its members to successfully adapt to environmental conditions and to better exploit food resources [..]

9	0   0 evolution Darwin’s definition: descent with modification. The term has been variously used and abused since Darwin to include everything from the origin of man to the origin of life.

10	0   0 evolution The life of the software after its initial development cycle; any subsequent cycle, during which the product evolves. [D04726]

11	0   0 evolution Evolution is the process of using Candy to change a Pokémon into an individual of an evolved species of Pokémon.

12	0   0 evolution A law of biology that states that all living organisms on this planet are related through descent from a common ancestor. The guiding principle of all modern biology. "Darwin’s theory of [..]

13	0   0 evolution development: a process in which something passes by degrees to a different stage (especially a more advanced or mature stage); "the development of his ideas took many years"; [..]

14	0   0 evolution development, an unfolding

15	0   0 evolution n. Development or growth.

16	0   0 evolution Evolution is a process that results in changes in the genetic material of a population over time

17	0   0 evolution The theory that living organisms mutate and change, generally from simple to increasingly complex forms.

18	0   0 evolution The change of biological organisms by means of the adaptation to the demands of the physical environment. Organisms that successfully adapt pass on their genes to future generations thereby changing the species itself.

19	0   0 evolution The process that involves a gradual change in a population’s appearnace that has happened over many generations.

20	0   0 evolution evolutsye

21	0   0 evolution evolution (pop)

22	0   0 evolution When a species slowly develops, changes and adapts. Scientists believe humans evolved from apes.

23	0   0 evolution Evolution is a process of change over time. Generally the term evolution is used and understood as part of the Darwinian theory of evolution in which species are believed to have changed over time as [..]

24	0   0 evolution The process by which life forms of all kinds—from viruses

25	0   0 evolution   Natural selection, the survival of the fittest, is the driving force behind evolution and is measured by a species viability and fecundity. Governed by Darwin’s theory of evolution by natural [..]

26	0   0 evolution An introduction is provided to modern evolutionary theory, population and evolutionary genetics in order to understand the fundamental processes and the genetic make-up of populations.

27	0   0 evolution Change over time

28	0   0 evolution (L: ex=out of; volvere= to roll; to evolve) 1) the concept that life comes only from existing life, and that living things change, giving rise to new life forms. 2) gradual development from a simple f [..]

29

0   0 evolution The theory of evolution as initially formulated by Charles Darwin in 1859 is the central theory of biology. All processes that enable life are the result of the process of evolution over a period estimated to be more than 3 billion years. The mechanism of evolution are mutation and natural selection. These two processes result in changes at the gen [..]

30	0   0 evolution a natural process whereby mutations and recombinations of DNA change in frequency in a population over time due to the differential fitness they confer. Evolution explains the vast diversity of life o [..]

31	0   0 evolution The process by which a population of interbreeding individuals changes over time.

32	0   0 evolution A series of changes, some gradual and some sporadic, that accounts for the present form and function* of objects.

33	0   0 evolution the transformation of a species of organic life over long periods of time (macroevolution) or from one generation to the next (microevolution) due to four evolutionary forces. Anthropologists study both the cultural and biological evolution of the human species.

34	0   0 evolution The development of species over time, caused by heritable traits in the population changing from generation to generation, often in response to environmental pressures that favour certain characterist [..]

35	0   0 evolution Changes in species as a consequence of processes such as mutation and natural selection.

36	0   0 evolution The passing of Spirit into form.

37	0   0 evolution A process in which a population of self-replicating entities undergoes variation, with successful variants spreading and becoming the basis for further variation.

38	0   0 evolution [1] a biological process relating to change in form over time, leading to the rise of new species; [2] a non-biological process relating to gradual change, often from a simple to a more complex form [evolutionary; evolve; evolving]

39	0   0 evolution scientific theory that all animals and plants can have continuous change to adopt to their environment.

40	0   0 evolution Evolution is a process involving the development or growth of something. It describes changes over a period of time that typically result in a better or more complex version of the original form. In t [..]

41	0   0 evolution (n) a process in which something passes by degrees to a different stage (especially a more advanced or mature stage)(n) (biology) the sequence of events involved in the evolutionary development of a [..]

42	0   0 evolution A very slow growth or change.

43	0   0 evolution Darwin’s theory is that different forms of animal and vegetable life are due to small variations, and that natural selection is a main agent in bringing them about. If favourable, these varia [..]

44	0   0 evolution its process, according to biologists.

45	0   0 evolution A change in the traits of living organisms over generations, including the emergence of new species.

46	0   0 evolution n. evolución

47

0   0 evolution A scientific explanation of the development of life from the earliest one-celled animals to the variety of species we see today. The major assertion here is not that there is variation within a species—which is obvious—but that variation can be so fundamental that a new species arises. The mechanism of evolution is Natural Selection. This process [..]

48	0   0 evolution The change in the gene pool of a population from generation to generation by such processes as mutation, natural selection, and genetic drift

49	0   0 evolution The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.

50	0   0 evolution Chemical and physical transformation of the biogenic Elements from their nucleosynthesis in stars to their incorporation and subsequent modification in planetary bodies and terrestrial Biochemistry. I [..]

51	0   0 evolution The process of accumulation of genetic and epigenetic changes over Time in individual Cells and the effect of the changes on Cell Proliferation.

52	0   0 evolution The continuous developmental process of a Culture from simple to complex Forms and from homogeneous to heterogeneous qualities.

53	0   0 evolution The process of cumulative change at the level of DNA; RNA; and Proteins, over successive generations.

54	0   0 evolution The techniques used to produce molecules exhibiting properties that conform to the demands of the experimenter. These techniques combine methods of generating structural changes with methods of select [..]

55	0   0 evolution Creation and development of bodies within solar systems, includes study of early planetary Geology.

56	0   0 evolution Darwin described evolution as «descent with modification»: the change in a lineage of populations between generations. The theory of evolution has four main components: • Population geneti [..]

57	0   0 evolution Refers to any seamanship task that requires special effort or co-ordination. A replenishment at sea or a taking another ship under tow are considered evolutions.

58	0   0 evolution any activity where all hands, or at least a large number of men, work together to accomplish a specific task.

59	0   0 evolution The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.

60	0   0 evolution Chemical and physical transformation of the biogenic elements from their nucleosynthesis in stars to their incorporation and subsequent modification in planetary bodies and terrestrial biochemistry. I [..]

61	0   0 evolution Evolution at the molecular level of DNA sequences and proteins. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)

62	0   0 evolution Creation and development of bodies within solar systems, includes study of early planetary geology.

63	0   0 evolution Genetic change, change in a population’s gene pool from generation to generation (Darwin’s descent with modification).

64	0   0 evolution Evolution is the process by which different species of animals evolve, generally in accordance with natural selection and to make life more successful for the species. For example, certain species of [..]

65	0   0 evolution Uniform sequence of practiced steps by squad carrying out common tasks such as selection and placement of ladders, stowing hoses in hose bed

66	0   0 evolution Any gradual change. Organic evolution is any genetic change in organisms from generation to generation.

67	0   0 evolution The theoretical ability, as postulated by Darwin and others, of a species developing by degrees into a genetically and physically different organism, by a process known as natural selection.

68	0   0 evolution a scientific theory that animals and plants originated from other preexisting types, with distinguishable differences being due to modifications in successive generations resulting from natural select [..]

69	0   0 evolution The process by which all forms of plant and animal life change slowly over time because of slight variations in the genes that one generation passes down to the next.

70	0   0 evolution See Brief definitions

71	0   0 evolution The process of cumulative change occurring over successive generations.

72	0   0 evolution «Evolution is a process of complication of energy.» — Samael Aun Weor, The Perfect Matrimony (1950)

73	0   0 evolution The development of a species from its original to its present state; the theory that all species developed from earlier forms. p.154 Natural Selection:

74	0   0 evolution The process of a Pokémon changing into another Pokémon is known as Evolution. Evolved Pokémon are usually more powerful than their predecessors, and they can often learn moves that are more powerfu [..]

75	0   0 evolution A word peculiar to the military, with no connection to Charles Darwin. An Evolution is an «evolving» exercise, really any exercise. A flight is an evolution. A parade is an evolution. A ball [..]

76	0   0 evolution In Darwinian terms a gradual change in phenotypic frequencies in a population that results in individuals with improved reproductive success.

77	0   0 evolution The process by which novel traits arise in populations and are passed from generation to generation. Its action over time theoretically explains the origin of new species and biological diversity.

78

0   0 evolution In a broad sense, the origin of entities possessing different states of one or more characteristics and changes in the proportions of those entities over time. Organic evolution, or biological evolution, is a change over time in the proportions of individual organisms differing genetically in one or more traits. Such changes transpire by the origin [..]

79	0   0 evolution The change in organisms over generations that gradually results in changes in populations and species.

80	0   0 evolution Changes in allele frequencies over time.

81	0   0 evolution Evolution is a process that results in heritable changes in a population over many generations. Evolution occurs within populations not individuals. Charles Darwin’s Theory of Natural Selection sugg [..]

82	0   0 evolution Change of the genes of a population over time, resulting in new species.

83	0   0 evolution The process of cumulative change , usually gradual.

84	0   0 evolution Whether in the realm of culture or biology, the transformation of one form into another.

85	0   0 evolution evolution

86	0   0 evolution Genetically based changes in populations of organisms, occurring over successive generations.

87	0   0 evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspri [..]

88	0   0 evolution Evolution is the fifth studio album by American rock band Journey, released in March 1979 by Columbia Records. It is the band’s first album to feature drummer Steve Smith. It was the band’s most succe [..]

89	0   0 evolution GNOME Evolution (formerly Novell Evolution and Ximian Evolution, prior to Novell’s 2003 acquisition of Ximian) is the official personal information manager for GNOME. It has been an official part of G [..]

90	0   0 evolution Evolution is change in heritable traits of biological organisms over successive generations. Evolution also may refer to:

91	0   0 evolution Evolution is a collection of short stories that work together to form an episodic science fiction novel by author Stephen Baxter. It follows 565 million years of human evolution, from shrewlike mamma [..]

92	0   0 evolution Evolution: International Journal of Organic Evolution, is a monthly scientific journal that publishes significant new results of empirical or theoretical investigations concerning facts, processes, me [..]

93	0   0 evolution Evolution (進化論), is the eighth album of Twins and was released September 2003. The disc contains 10 songs.

94	0   0 evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspri [..]

95	0   0 evolution Evolution was a heel professional wrestling stable in WWE which was a part of the Raw brand from 2003 to 2005, as well as during 2007 and 2014. At the height of its original existence, the group consi [..]

96	0   0 evolution Evolution is a 2001 American comic science fiction film directed by Ivan Reitman. It stars David Duchovny, Orlando Jones, Seann William Scott, Julianne Moore, and Ted Levine. It was released by Dream [..]

97	0   0 evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspri [..]

98	0   0 evolution Evolution is the fourth studio album by American R&B quartet Boyz II Men, released in September 1997. It is their final album released on Motown Records. A Spanish language version, Evolución, wa [..]

99	0   0 evolution «Evolution» is the first episode of the third season of the syndicated American science fiction television series Star Trek: The Next Generation, the 49th episode overall, it first aired in the United [..]

100	0   0 evolution «Evolution» is a song recorded by Japanese recording artist and lyricist Ayumi Hamasaki, released on January 31, 2001, as the second single from her fourth studio album I Am… (2002). «Evolution» is [..]

101	0   0 evolution Decoded Feedback is a Canadian musical project which incorporates styles of electro-industrial and aggrotech. The duo releases music on the North American distributor Metropolis Records, and the Europ [..]

102	0   0 evolution Evolution is the first of two albums released in 1967 by British pop rock band the Hollies. It is their sixth UK album and peaked at number 13 in the UK album chart.

103	0   0 evolution Evolution is an original novel written by John Peel and based on the long-running British science fiction television series Doctor Who. features the Fourth Doctor and Sarah.

104	0   0 evolution Evolution is a large thrill ride manufactured by FarFabbri in Italy. It consists of four inclined pillars which support a revolving arm. On one end of the arm are some counterweights and on the other [..]

105	0   0 evolution Evolution is a 2001 documentary series by the American broadcaster Public Broadcasting Service (PBS) and WGBH on evolutionary biology, from the producers of NOVA.

106	0   0 evolution Evolution is the third album by Brazilian heavy metal band Viper, release in 1992.

107	0   0 evolution Edge of Sanity was a Swedish death metal band that, alongside Opeth, is commonly regarded as being the first to fuse extreme metal styles like death and black metal with progressive rock. The group wa [..]

108	0   0 evolution Evolution, also called The Evolution Of Beauty, is an advertising campaign launched by Unilever in 2006 as part of its Dove Campaign for Real Beauty, to promote the newly created Dove Self-Esteem Fund [..]

109	0   0 evolution Evolution is the fourth studio album by American country music artist Martina McBride. It was released in August 1997 by RCA Records. The album produced six singles, all of which have charted on the U [..]

110	0   0 evolution Evolution is an EP by American indie rock group Open Hand. It was recorded by Justin Isham at The Loft in Los Angeles, California in January 2000, and released by the American Propaganda label. Guest [..]

111	0   0 evolution «Evolution» is a song by American nu metal band Korn. The song was the first single to be released from the band’s untitled album on June 12, 2007. It is one of the four tracks in which Brooks Wackerm [..]

112	0   0 evolution Evolution is the sixth studio album by guitarist Tony MacAlpine, released on October 10, 1995 through Shrapnel Records.

113	0   0 evolution Evolution is the 12th album by Masami Okui, released on 4 October 2006. The album title came from Okui’s independent record label company name Evolution.

114	0   0 evolution Evolution is a weekly radio show hosted by Markus Schulz on the Sirius XM Radio network. The show began in June 2008 and features two 1 hour continuous mixes. Evolution originally aired exclusively on [..]

115	0   0 evolution Evolution (The Most Recent) is an album by American blues artist Taj Mahal, which was released in 1977.

116	0   0 evolution Evolution is the fourth album (second published worldwide) by the American vocalist, pianist and songwriter Oleta Adams and was released in 1993. The album is the follow up to Adams’ worldwide hit alb [..]

117	0   0 evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspri [..]

118	0   0 evolution Evolution is the fourth EP released by the anarcho-punk band Subhumans. It was also the band’s first vinyl release on their own label, Bluurg Records (bar the «Wessex ’82» split EP). The EP was also r [..]

119	0   0 evolution Evolution is the debut album led by the American trombonist Grachan Moncur III, recorded in 1963 and released on the Blue Note label. Moncur’s band consists of alto saxophonist Jackie McLean, trumpe [..]

120	0   0 evolution Evolution (French: Évolution) is a 1971 Canadian animated short by Michael Mills, offering a humorous portrayal of evolution. Evolution was nominated for the Academy Award for Best Animated Short Fil [..]

121	0   0 evolution «Evolution» is the second EP by the South Korean boy band Infinite. The song «BTD (Before the Dawn)» was used to promote the EP. They released the song «Voice of My Heart» on December 29, 2010 as a te [..]

122	0   0 evolution Evolution is the tenth album by progressive rock band Nektar, released in 2004. It was the first Nektar album since 1977’s Magic Is a Child to feature original drummer Ron Howden, who rejoined other [..]

123	0   0 evolution Evolution is the third album by Latin Rock band Malo, released in 1973. The album has been reissued on CD in 2001 as one of the discs in Rhino Handmade’s Celebración box set, with the addition of sin [..]

124	0   0 evolution Evolution is the second album by session guitarist Dennis Coffey and the Detroit Guitar Army.

125	0   0 evolution Evolution is the sixth studio album by Paul van Dyk released in April 2012. The album features a wide range of collaborations including Arty, Giuseppe Ottaviani, Adam Young, Austin Leeds, Plumb, Johnn [..]

126	0   0 evolution Evolution is the sixth studio album by Paul van Dyk released in April 2012. The album features a wide range of collaborations including Arty, Giuseppe Ottaviani, Adam Young, Austin Leeds, Plumb, Johnn [..]

127	0   0 evolution Evolution is the fourth studio album by British boy band JLS. The album was released on 5 November 2012 through RCA Records. The album marks a new change in direction for the band, described as «a thr [..]

128	0   0 evolution Evolution is the seventh studio album by Detroit hip hop group Slum Village. The album was released on June 25, 2013, by Ne’Astra Music and Traffic Entertainment Group. The album features guest appear [..]

129	0   0 evolution Evolution is the fifth studio album by American electronica duo Blood on the Dance Floor, released internationally on June 19, 2012. It is their first release to appear on the US Billboard 200, and is [..]

130	0   0 evolution Evolution is a retrospective compilation album by the English rock band Magnum, released by SPV/Steamhammer on 11 November 2011 in Germany and 14 November in the UK and the rest of Europe. The album m [..]

131	0   0 evolution Evolution (2012) is the fifth studio album by Greek thrash metal band Memorain. It was released on 7 August 2012 by Metal Maple Records.

132	0   0 evolution Evolution is an album by jazz vibraphonist and pianist Teddy Charles recorded in 1953 and 1955 for the Prestige label.

133	0   0 evolution EVolution is a research project funded by the European Commission under The 7th Framework Programme of the Green Cars initiative. It started on 1 October 2012 with a specified duration of 4 years. The [..]

134	0   0 evolution Evolution is a radio station platform on iHeartRadio and on Clear Channel’s HD2 & HD3 radio and FM translators across the United States that plays commercial free Dance/EDM music 24/7, operated by [..]

135	0   0 evolution Evolution is the ninth studio album by Hed PE released through Pavement Music. This marks the last appearance of Mawk and Jaxon.

136	0   0 evolution Evolution (エボリューション, Eboryūshon) is a professional wrestling stable in the All Japan Pro Wrestling (AJPW) promotion. Originally started as a tag team named Last Revolution (ラスト� [..]

137	0   0 evolution Evolution was a darknet market operating on the Tor network. The site was founded by an individual known as ‘Verto’ who also founded the now defunct Tor Carding Forum. Evolution was active between 14t [..]

138	0   0 evolution Evolution: The Origin of Species is a card game created by Dmitriy Knorre and Sergey Machin in 2010. The game is inspired by the evolutionary biology. It was published by SIA Rightgames RBG. Engli [..]

139	0   0 evolution Evolution (French: Évolution) is a 2015 French horror-thriller film directed by Lucile Hadžihalilović. It was shown in the Vanguard section of the 2015 Toronto International Film Festival.

140	0   0 evolution Evolution (stylized as EVØLUTION) is the third studio album by the American electronic rock band Ghost Town. It was released on November 6, 2015 through Fueled by Ramen. The first single from the alb [..]

141	0   0 evolution Evolution (stylized as EVOLution) is the second studio album by American singer Sabrina Carpenter, released on October 14, 2016, by Hollywood Records. Sabrina began recording the album in 2015, shortl [..]

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