Aarushhh/wikipedia-simple-splitted huggingface dataset:
Natural selection 

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:
 All living things have such fertility that their population size could increase rapidly forever.
 However, population sizes do not increase forever. Mostly, population sizes remain about the same.
 Food and other resources are limited. Therefore, there is competition for food and resources.
 No two individuals are alike. Therefore, they will not have the same chances to live and reproduce.
 Much of this variation can be inherited. Parents pass traits to their children through their genes.
 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. Natural selection is really a process of elimination.p117 The elimination is being caused by the relative fit between individuals and the environment they live in.
Selection in natural populations 
There are now many cases where natural selection has been proved to occur in wild populations. Almost every case investigated of camouflage, mimicry and polymorphism has shown strong effects of selection.

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.p182 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. Therefore, lactase persistence is often cited as an example of recent human evolution. As lactase persistence is genetic, but animal husbandry a cultural trait, that is gene–culture coevolution.

Adaptation
Adaptation 

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

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). A favourite example used today to study the interplay of adaptation and speciation is the evolution of cichlid fish in African rivers and lakes.

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 modern 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.

Limitations 
Not all features of an organism are adaptations.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
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.p29 It is therefore "a very weak evolutionary force in large populations".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.
Drift reduces genetic variation in populations, potentially reducing a population’s ability to survive new selective pressures.
 Genetic drift acts faster and has more drastic results in smaller populations. Small populations usually become extinct.
 Genetic drift may contribute to speciation (starting a new species) if the small group does survive.
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. ♦ 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.
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.
Species 

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.

Species splitting 
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. 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".
This was an early account of the importance of geographical separation. Another biologist who thought geographical separation was critical was Ernst Mayr.
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.

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.

Modern evolutionary synthesis 

This was an important movement in evolutionary biology, which started in the 1930s and finished in the 1950s. 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. Sewall Wright explained genetic drift in 1931.
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.
Thinking in terms of populations, rather than individuals, is important. The genetic variety existing in natural populations is a key factor in evolution.
Evolution and fossils: the same factors which act today also acted in the past.
Gradualism: evolution is gradual, and usually takes place by small steps. There are some exceptions to this, notably polyploidy, especially in plants.
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.
Genetic drift can be important in small populations.
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.p292, 397

Some areas of research

Co-evolution
Co-evolution 

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. 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.
Tree of life 
 
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. Below is a simplified version of present-day understanding.

Macroevolution
Macroevolution 

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.p87 For some palaeontologists, what they see in the fossil record cannot be explained just by the gradualist evolutionary synthesis. They are in the minority.

Altruism and group selection
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. 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.
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. The warning note from Ernst Mayr, and the work of William Hamilton are both important to this discussion.

Hamilton's equation 
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:
  is the reproductive cost to the altruist,
  is the reproductive benefit to the recipient of the altruistic behavior, and
  is the probability, above the population average, of the individuals sharing an altruistic gene – the "degree of relatedness".

Sexual reproduction
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.

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.

"When populations are outcrossed 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 populations, individuals are largely homozygous and recombination has no effect".
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. 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.

What evolution is used for today 
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.
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 
In 2010 the journal Nature selected 15 topics as 'Evolution gems'. These were:

Gems from the fossil record 
Land-living ancestors of whales
From water to land (see tetrapod)
The origin of feathers (see origin of birds)
The evolutionary history of teeth
The origin of vertebrate skeleton
Gems from habitats 
Natural selection in speciation
Natural selection in lizards
A case of co-adaptation
Differential dispersal in wild birds
Selective survival in wild guppies
Evolutionary history matters

Gems from molecular processes 
Darwin's Galapagos finches
Microevolution meets macroevolution
Toxin resistance in snakes and clams
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.

Responses to the idea of evolution

Debates about the fact of evolution 

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. 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.

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. 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.
Other fields, like cosmology and earth science 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
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

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

Using evolution for other purposes 
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 
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.

Eugenics
Eugenics 

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

Social Darwinism 
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. Today, most biologists and philosophers say that the theory of evolution should not be applied to social policy.

Controversy 
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.

Further reading
Further reading

Evidence for evolution 
These books are mostly about the evidence for evolution.
Coyne, Jerry A. 2009 Why evolution is true. Oxford University Press, Oxford.  (pbk)
Dawkins, Richard 2009. The greatest show on Earth. Bantam, London.  (hbk)
Futuyma D.J. 1983. Science on trial: the case for evolution. Pantheon Books, New York. ; 2nd ed 1995 Sinauer Associates, Sunderland, Massachusetts. .
Prothero, Donald R. 2007. Evolution: what the fossils say and why it matters. Columbia University Press, New York.  (hbk)
The process of evolution
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. . Strong in molecular evolution; brings together molecular biology with evolutionary concepts.
Futuyma D.J. 1979. Evolutionary biology. 1st ed. Sinauer Associates, Sunderland, Massachusetts. ; 2nd ed 1986 Sinauer. ; 3rd ed 1998 Sinauer. . Widely used textbook, available second-hand. For students and teachers.
 Futuyma D.J. 2005. Evolution. Sinauer Associates, Sunderland, Massachusetts. ; 2nd ed 2009 Sinauer. . Successor to above; but basically a different book. For students and teachers.
Freeman, Scott & Herron, Jon; 1997. Evolutionary analysis. Prentice Hall ; 2nd ed 2000 ; 3rd ed 2004 Cummings ; 4th ed 2007 Cummings . Modern topics such as phylogenetic trees based on genomics, genetics, molecular biology. Has website:   For students and teachers.
Ridley, Mark 1993. Evolution. Blackwell ; 2nd ed 1996 Wiley-Blackwell ; 3rd ed 2003 Wiley . Comprehensive: case studies, commentary, dedicated website and CD. For students and teachers.
 Mayr, Ernst. 2001. What evolution is. Weidenfeld & Nicolson, London. . Clearly written, for a general audience.
Related pages
Evolutionary biology
Coevolution
Human evolution
Adaptation
Natural selection
Sociobiology

References

Other websites 

 
 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
Up to 1900 
 192 - Narcissus murders Roman Emperor Commodus.
 406 - Vandals, Alans and Suebians cross the Rhine, beginning the invasion of Gaul.
 1225 – The Ly Dynasty in Vietnam ends after 216 years, as Tran Thai Tong, still a boy, becomes Emperor. This is the beginning of the Tran Dynasty.
 1472 – The throwing of snowballs is banned in Amsterdam.
 1494 - First Italian War: Troops of King Charles VIII of France enter Rome.
 1600 – The British East India Company is created.
 1660 - James II of England is named Duke of Normandy by Louis XIV of France.
 1687 - The first Huguenots set sail from France for the Cape of Good Hope.
 1695 - Window tax is introduced in England. As a result, many people brick up their windows in order not to have to pay the tax.
 1703 – An earthquake and tsunami damage Tokyo, Odawara and several nearby towns, killing around 10,000 people.
 1720 – A storm flood ravages the North German coast, separating a dune on Heligoland from the main island.
1775 – American Revolutionary War: In the Battle of Quebec, British forces repulse an attack by Continental Army General Richard Montgomery.
 1790 - Efimeris, the oldest Greek newspaper still in print, is published for the first time.
 1796 - Baltimore, Maryland, is incorporated as a city.
 1857 – Queen Victoria chooses Ottawa as the capital of Canada.
 1862 – Abraham Lincoln signs the Act creating the state of West Virginia and thus splitting Virginia in two.
 1862 - American Civil War: The Battle of Stones River in Tennessee begins.
 1862 - The battleship USS Monitor sinks in a storm in heavy seas off Cape Hatteras, North Carolina.
 1878 - In Mannheim, Germany, Karl Benz files a patent on his reliable two-stroke gas engine.
 1879 – Thomas Edison publicly demonstrates incandescent light in Menlo Park, New Jersey.
 1891 – A new immigration depot is opened on Ellis Island, New York.
1901  2000 
 1904 – What is now Times Square, New York, holds its first New Year celebration.
 1909 – The Manhattan Bridge is opened.
 1917 - British troop transporter Osmanieh hits a mine laid by German U-boat UC 34 off Alexandria, Egypt, sinking with 99 deaths.
 1923 – The BBC broadcasts the chimes of Big Ben in London for the first time.
 1929 - The Glen Cinema Disaster in Paisley, Scotland, kills 70 children.
 1944 – World War II: Hungary declares war on Germany.
 1946 – President of the United States Harry S. Truman officially declares an end to hostilities in World War II.
 1948 - The 100,000th landing of the Berlin Airlift occurs.
 1951 - The Marshall Plan expires after giving over $ 13.3 billion to help war-torn parts of Europe.
 1955 - General Motors becomes the first US Corporation to make over a billion US Dollars in a year.
 1960 - The farthing coin stops being the legal tender in the United Kingdom.
1963 – The Central African Federation officially breaks apart, and eventually becomes Zambia, Malawi and Rhodesia.
 1964 – A three-day census in East Germany ends, determining the population to be 17,003,632.
 1965 – Jean-Bedel Bokassa leads a coup against David Dacko in the Central African Republic.
 1968 – Marien Ngouabi becomes President of the Republic of the Congo.
 1973 - AC/DC is formed.
 1981 – In a military coup in Ghana, Jerry Rawlings takes control.
 1983 – A military coup in Nigeria is led by Muhammadu Buhari.
 1986 – In San Juan, Puerto Rico a fire at the Dupont Plaza Hotel kills 97 people.
 1987 – Robert Mugabe becomes President of Zimbabwe.
 1988 - Pittsburgh Penguins' Mario Lemieux becomes the only NHL player, to this date, to score goals in five different ways - even strength, shorthand, power play, penalty shot and empty net, in an 8-6 win over the New Jersey Devils.
 1989 – Arved Fuchs and Reinhold Messner reach the South Pole on their cross-Antarctica journey.
1990 – Garry Kasparov successfully defends his world chess title against Anatoly Karpov.
 1991 – The Soviet Union officially comes to an end.
 1992 – Czechoslovakia peacefully dissolves, splitting into the Czech Republic and Slovakia the next day.
 1994 – This date is skipped altogether in Kiribati, as the International Date Line is shifted to the east of the Line Islands and Phoenix Islands.
 1999 – Boris Yeltsin resigns as President of Russia.
 1999 – The Panama Canal is transferred from US control to Panama's control.
From 2001 
 2004 – The Taipei 101 tower is opened in Taipei, Taiwan.
 2006 - The total of US troops killed in the Iraq War reaches 3,000.
 2009 – In Espoo, Finland, Ibrahim Shkupolli shoots his former girlfriend dead, then shoots four people to death at a shopping mall before committing suicide.
 2009 – The Ignalina power station in Lithuania is shut down.
 2014 - The first same-sex marriages in Scotland take place.
 2014 - US and UK forces withdraw from Afghanistan.
 2014 - Beji Caid Essebsi becomes President of Tunisia.
 2014 - A crush at a New Year celebration in Shanghai kills 36 people.
 2015 - Fire breaks out at a hotel near the Burj Khalifa in Dubai.
 2016 - Bomb attacks in Baghdad kill at least 28 people.
 2017 - A bus crash near Migaa, Kenya, kills at least 36 people.

Births
Up to 1900 
 695 – Muhammad bin Qasim al-Thaqafi, founded Islam in South Asia (d. 715)
 1378 – Pope Callixtus III (d. 1458)
 1491 – Jacques Cartier, French explorer (d. 1557)
 1499 - Diane de Poitiers (d. 1566)
 1514 - Andreas Vesalius, Flemish anatomist (d. 1564)
 1572 – Emperor Go-Yozei of Japan (d. 1617)
 1585 - Gonzalo Fernandez de Cordoba, Spanish military leader and politician (d. 1645)
 1668 - Herman Boerhaave, Dutch humanist and physician (d. 1738)
 1720 – Charles Edward Stuart, pretender to the British throne (d. 1788)
 1738 – Charles Cornwallis, 1st Marquess Cornwallis, British general (d. 1805)
 1741 – Isabella Maria of Parma (d. 1763)
 1798 - Friedrich Robert Faehlmann, Estonian physician, philologist and academic (d. 1850)
 1815 - George G. Meade, American general and engineer (d. 1872)
 1830 – Isma'il Pasha, Governor of Egypt (d. 1895)
 1830 - Alexander Smith, Scottish poet (d. 1861)
 1838 - Emile Loubet, President of France (d. 1929)
 1842 – Giovanni Boldini, Italian painter (d. 1931)
1844 - Ebe W. Tunnell, Governor of Delaware (d. 1917)
 1846 - Ferdinand Domela Nieuwenhuis, Dutch politician (d. 1919)
 1855 – Giovanni Pascoli, Italian poet (d. 1912)
 1857 - King Kelly, American baseball player (d. 1894)
 1860 - Berthold Lasker, German chess player (d. 1928)
 1863 – Alfredo Panzini, Italian writer (d. 1939)
 1864 - Hans am Ende, German painter (d. 1918)
 1864 - Robert Grant Aitken, American astronomer (d. 1951)
 1869 – Henri Matisse, French painter (d. 1954)
 1874 - Julius Meier, German-American politician, 20th Governor of Oregon (d. 1937)
 1877 – Viktor Dyk, Czech poet, dramatist and politician (d. 1931)
 1878 – Elizabeth Arden, Canadian businesswoman (d. 1966)
 1878 – Horacio Quiroga, Argentine-Uruguayan writer (d. 1937)
 1880 – George Marshall, 50th United States Secretary of State (d. 1959)
 1880 - Fred Beebe, American baseball player (d. 1957)
 1881 – Max Pechstein, German painter (d. 1955)
 1884 – Bobby Byrne, American baseball player (d. 1964)
1885 - Princess Victoria Adelaide of Schleswig-Holstein (d. 1970)
 1899 – Silvestre Revueltas, Mexican composer (d. 1940)
1901  1950 
 1901 - Karl-August Fagerholm, Prime Minister of Finland (d. 1984)
 1903 - Nathan Milstein, Ukrainian-born violinist (d. 1992)
 1904 - Umm Kulthum, Egyptian singer (d. 1975)
 1905 - Jules Styne, American songwriter (d. 1994)
 1905 - Guido Mollet, Prime Minister of France (d. 1975)
 1908 – Simon Wiesenthal, Austrian Holocaust survivor (d. 2005)
 1909 - Jonah Jones, American jazz trumpeter (d. 2000)
 1910 - Archie M. Gubbrud, Governor of South Dakota (d. 1987)
 1914 - Yrjö Nikkanen, Finnish javelin thrower (d. 1985)
 1918 - Ray Graves, American football player and coach (d. 2015)
 1919 - Recy Taylor, American rape victim and civil rights activist (d. 2017)
 1924 - Kjell Arnljot Wig, Norwegian media personality (d. 2015)
 1924 – Taylor Mead, American actor (d. 2013)
 1928 - Hugh McElhenny, American football player
 1928 – Amarillo Slim, American professional poker player (d. 2012)
 1928 - Veijo Meri, Finnish writer (d. 2015)
 1928 - Siné, French cartoonist (d. 2016)
1929 - Mies Bouwman, Dutch entertainer (d. 2018)
 1930 - Odetta, American singer (d. 2008)
 1931 - George Ardisson, Italian actor (d. 2014)
 1931 - Tom Rolf, Swedish-American film editor (d. 2014)
 1931 – Mildred Scheel, German physician, cancer campaigner and First Lady (d. 1985)
 1934 - Michael Bonallack, English golfer
 1935 – Peter Herbolzheimer, German musician (d. 2010)
 1935 - King Salman of Saudi Arabia
 1936 – Siw Malmkvist, Swedish singer
 1936 - Umaru Dikko, Nigerian politician (d. 2014)
 1937 – Avram Hershko, Israeli biologist
 1937 – Anthony Hopkins, Welsh actor
 1937 - Carl Emil Christiansen, Danish footballer (d. 2018)
 1938 – Rosalind Cash, American actress (d. 1995)
 1938 - Marien Ngouabi, Congolese politician (d. 1977)
 1939 - Peter Camejo, American politician (d. 2008)
 1940 - Tim Considine, American actor
 1941 – Alex Ferguson, Scottish football manager
 1941 - Sean S. Cunningham, American movie director and writer
 1941 - Sarah Miles, English actress
1942 - Taufiq Kiemas, First Gentleman of Indonesia (d. 2013)
 1942 – Andy Summers, British guitarist
 1943 – Ben Kingsley, British actor
 1943 – John Denver, American singer-songwriter (d. 1997)
 1943 - Pete Quaife, British musician (d. 2010)
 1944 - Neil Ross, American voice actor
 1944 – Taylor Hackford, American director and producer
 1945 - Diane von Fürstenberg, Belgian-American fashion designer
 1946 - Lyudmila Pakhamova, Soviet ice dancer (d. 1986)
 1946 - Boris Dubin, Russian sociologist and translator (d. 2014)
 1947 - Burton Cummings, Canadian keyboardist
 1947 - Tim Matheson, American actor
 1948 – Donna Summer, American disco singer (d. 2012)
 1948 - Sandy Jardine, Scottish footballer (d. 2014)
 1948 - Joe Dallesandro, American actor
 1948 - Viktor Mikhailovich Afanasyev, Soviet-Russian cosmonaut
1951  1975 
 1951 – Tom Hamilton, American bassist (Aerosmith)
 1954 – Alex Salmond, Scottish politician, 4th First Minister of Scotland
 1954 – Hermann Tilke, German racing circuit designer
 1954 – Ingibjorg Solrun Gisladottir, Icelandic politician
 1956 - Robert Goodwill, English politician
 1958 – Bebe Neuwirth, American actress
 1959 – Baron Waqa, Nauruan musician and politician, President of Nauru
 1959 – Val Kilmer, American actor
 1959 – Paul Westerberg, American musician
 1960 – Steve Bruce, English footballer
 1960 – John Allen Muhammad, American spree killer (d. 2009)
 1961 - Rick Aguilera, American baseball player
 1961 - Jeremy Heywood, English economist and civil servant
 1963 - Scott Ian, American guitarist
 1964 - Michael McDonald, American actor and comedian
 1965 – Gong Li, Chinese actress
 1965 – Nicholas Sparks, American writer
 1966 - Lisa Joyner, American journalist and actress
 1970 – Bryon Russell, American basketball player
 1972 – Grégory Coupet, French footballer
From 1976 
 1976 - Matthew Hoggard, English cricketer
 1977 - Psy, South Korean rapper
 1977 - Donald Trump Jr., son of Donald Trump
 1979 – Bob Bryar, drummer in My Chemical Romance
 1980 – Richie McCaw, New Zealand rugby player
 1980 – Fumie Suguri, Japanese figure skater
 1981 – Margaret Simpson, Ghanaian athlete
 1981 - Nathan Robinson, Canadian ice hockey player
 1982 – Craig Gordon, Scottish footballer
 1984 – Corey Crawford, Canadian ice hockey goaltender
 1984 - Calvin Zola, Congolese footballer
 1986 - Bronson Pelletier, Canadian actor
 1987 - Javaris Crittenton, American basketball player
 1987 - Emilie Le Pennec, French gymnast
 1990 – Patrick Chan, Canadian figure skater
 1991 - Camila Giorgi, Italian tennis player
 1995 - Gabrielle Douglas, American gymnast

Deaths
Up to 1900 
 192 – Commodus, Roman Emperor (b. 161)
 335 – Saint Silvester, Pope and Saint whose day is marked on December 31
 669 - Li Shiji, Chinese chancellor (b. 594)
 1164 – Margrave Ottokar III of Styria (b. 1124)
 1194 – Leopold V of Austria (killed at a tournament) (b. 1157)
 1302 - Frederick III, Duke of Lorraine (b. 1238)
 1384 – John Wyclif, English theologian (b. 1328)
 1460 - Richard Neville, 5th Earl of Salisbury (b. 1400)
 1510 – Bianca Maria Sforza, wife of Maximilian I, Holy Roman Emperor (b. 1472)
 1568 – Shimazu Tadayoshi, Japanese daimyo (b. 1493)
 1650 – Dorgon, Emperor of China (b. 1612)
 1679 - Giovanni Alfonso Borelli, Italian physiologist and physicist (b. 1608)
 1705 - Catherine of Braganza (b. 1638)
 1719 - John Flamsteed, English astronomer (b. 1646)
 1742 - Karl III Philip, Elector Palatine (b. 1661)
 1830 - Stéphanie Félicité, comtesse de Genlis, French writer (b. 1746)
 1857 - Edward Williams Clay, American artist (b. 1799)
 1865 - Fredrika Bremer, Swedish writer (b. 1801)
1872 – Aleksis Kivi, Finnish writer (b. 1834)
 1876 - Catherine Labouré, French nun and saint (b. 1806)
 1877 – Gustave Courbet, French painter (b. 1819)
 1882 - Léon Gambetta, French politician (b. 1838)
 1888 – Samson Raphael Hirsch, rabbi (b. 1808)
 1894 - Thomas Joannes Stieltjes, Dutch mathematician (b. 1856)
1901  2000 
 1905 - Alexander Popov, Russian physicist (b. 1859)
 1936 – Miguel de Unamuno, Spanish writer, philosopher (b. 1864)
 1948 – Malcolm Campbell, English Grand Prix race car driver (b. 1885)
 1950 – Karl Renner, President of Austria (b. 1870)
 1964 – Olafur Thors, five-time Prime Minister of Iceland (b. 1892)
 1964 – Bobby Byrne, American baseball player (b. 1884)
 1969 – George Lewis, jazz musician (b. 1900)
 1972 – Roberto Clemente, Baseball Hall of Famer (b. 1934)
 1972 - Henry Gerber, German-American activist (b. 1892)
 1977 – Sabah III Al-Salim Al-Sabah, Emir of Kuwait (b. 1924)
 1980 – Marshall McLuhan, Canadian writer (b. 1911)
 1980 – Raoul Walsh, movie director (b. 1887)
 1985 – Ricky Nelson, American singer (b. 1940)
 1989 - Gerhard Schröder, German politician (b. 1910)
 1990 – Vasili Lazarev, Soviet cosmonaut (b. 1928)
 1993 – Zviad Gamsakhurdia, scientist and writer, first President of the Republic of Georgia (b. 1939)
 1993 – Brandon Teena, American murder victim (b. 1972)
1994 – Bruno Pezzey, Austrian footballer (b. 1955)
 1997 – Floyd Cramer, musician (b. 1933)
 1997 – Michael Kennedy, son of Robert F. Kennedy, killed in a skiing accident on Aspen Mountain in Colorado (b. 1958).
 1999 – Elliot Richardson, American politician (b. 1920)
 2000 – Alan Cranston, American politician (b. 1914)
 2000 – José Greco, Spanish Flamenco dancer (b. 1918)
From 2001 
 2003 – Arthur R. von Hippel, German-born American scientist and professor at MIT (b. 1898)
 2004 – Gérard Debreu, French economist (b. 1921)
 2006 – Liese Prokop, Austrian politician (b. 1941)
 2007 – Ettore Sottsass, Italian architect (b. 1917)
 2008 – Donald E. Westlake, American writer (b. 1933)
 2009 - Rashidi Kawawa, former Prime Minister of Tanzania (b. 1926)
 2009 - Cahal Daly, Irish cardinal and archbishop (b. 1917)
 2010 – Syd Ward, New Zealand cricketer (b. 1907)
 2013 - John Fortune, English comedian (b. 1939)
 2013 - Johnny Orr, American basketball player and coach (b. 1927)
 2013 - James Avery, American actor (b. 1945)
 2014 - Arthur Valerian Wellesley, 8th Duke of Wellington, English aristocrat and army officer (b. 1915)
 2014 - Edward Herrmann, American actor (b. 1943)
 2015 - Marvin Panch, American racing driver (b. 1926)
 2015 - Dal Richards, Canadian big band leader (b. 1918)
 2015 - Wayne Rogers, American actor (b. 1933)
 2015 - Natalie Cole, American singer (b. 1950)
2015 - Beth Howland, American actress (b. 1941)
 2016 - William Christopher, American actor (b. 1932)
 2016 - Prince Dimitri Romanov, Russian prince (b. 1926)
 2016 - Henning Christophersen, Danish politician (b. 1939)
 2017 - Prince François, Count of Clermont, French nobleman, self-styled Dauphin of France (b. 1961)
 2021 - Betty White, American actress and comedian (b. 1922)
Holidays 
 New Year's Eve, including Hogmanay (Scotland) and Calennig (Wales)
 St. Sylvester's Day
 Ōmisoka (Japan)

Days of the year
Christmas is celebrated on this day in many Christian and Western countries.

Events
Up to 1900 
 333 - Roman Emperor Constantine I promotes his youngest son Constans to the rank of Caesar.
 336 - Ancient Rome holds its first documented Christmas celebration.
 496 - Clovis I, King of the Franks, is baptized into the Roman Catholic faith in Reims by Saint Remigius.
 597 - Augustine of Canterbury and his fellow labourers baptize over 10,000 Anglo-Saxons in Kent.
 800 – Coronation of Charlemagne as Holy Roman Emperor, in Rome.
 1000 - Hungary is established as a Christian kingdom by Stephen I of Hungary.
 1066 – Coronation of William the Conqueror as king of England, at Westminster Abbey, London.
 1130 - Roger II of Sicily is crowned the first King of Sicily.
 1223 – Saint Francis of Assisi assembles the first Nativity scene.
 1495 - Spanish forces defeat the Guanches, the native people of the Canary Islands, in the Battle of La Victoria de Acentejo - Tenerife is the last island to be taken over by Spain.
1553 - Battle of Tucapel: Mapuche rebels under Lautaro defeat the Spanish conquistadors and execute Governor of Chile Pedro de Valdivia.
 1599 – The city of Natal, Brazil is founded.
 1643 - Christmas Island is found and named in the Indian Ocean near present-day Indonesia by Captain William Mynors.
 1758 – Halley's Comet passes by Earth, just as Edmond Halley had predicted.
 1776 – George Washington and his army cross the Delaware River to attack the monarchy's Hessian mercenaries in Trenton, New Jersey.
 1818 – The first performance of "Silent Night" (Church of St. Nikolaus in Oberndorf, Austria).
 1837 – Battle of Okeechobee – United States forces defeat Seminole Native Americans.
 1868 – US President Andrew Johnson grants unconditional pardon to all Civil War rebels.
 1868 – Ezo Republic founded in Hokkaido by Shogunate rebels.
 1896 - John Philip Sousa composes The Stars and Stripes Forever.
1901  2000 
 1914 – Just after midnight on Christmas morning, German troops on the Western Front cease firing their guns and artillery and start singing Christmas carols.  Crossing the No man's land, they trade gifts with the enemy forces that face them.  The Christmas truce lasts for several days, depending on the location.
 1917 – Why Marry?, first dramatic play to win a Pulitzer Prize, opens at the Astor Theatre in New York City.
 1926 – Hirohito becomes Emperor of Japan, succeeding the Taisho Emperor (Yoshihito).
 1927 - The Vietnamese Nationalist Party is founded.
 1932 – A magnitude 7.6 earthquake in Gansu, China kills ~70,000 people
 1939 – Charles Dickens' A Christmas Carol was read on radio for the first time (CBS radio)
 1939 – Rudolph the Red-Nosed Reindeer is introduced by Montgomery Ward stores
 1941 – Hong Kong surrenders to the Japanese.
 1946 - The first European artificial chain reaction is initiated by the Soviet nuclear reactor F-1.
1947 – The Constitution of the Republic of China goes into effect.
 1952 – Queen Elizabeth II broadcasts her first Christmas message.
 1953 – A fire broke out in Shek Kip Mei, Hong Kong.
 1968 - Apollo 8 performs the very first successful Trans-Earth injection maneuver, sending crew and spacecraft on a trajectory back to Earth from lunar orbit.
 1968 - 42 Dalits are burned alive in Kilavenmani village in Tamil Nadu, India, a retaliation for a campaign for higher wages from Dalit labourers. The Dalits are at the bottom of India's class system, which consists of castes.
 1973 – The ARPANET crashes when a programming bug causes all ARPANET traffic to be routed through the server at Harvard University, causing the server to freeze.
 1974 – Cyclone Tracy devastates Darwin, Australia.
 1974 - Marshall Fields drives a vehicle through the gates of the White House, resulting in a four-hour stand-off.
 1977 – Prime Minister of Israel Menachem Begin meets in Egypt with President of Egypt Anwar Sadat
1989 – Nicolae Ceausescu, former communist dictator of Romania, and his wife Elena were condemned to death and executed under a wide range of charges by a court perceived by many as illegitimate.
 1990 – First trial run of the World Wide Web
 1991 – Mikhail Gorbachev resigns as president of the Soviet Union (the union itself is dissolved the next day).
From 2001 
 2002 – New Delhi Metro was introduced.
 2003 – The space probe Beagle 2 goes missing on the planet Mars.
 2004 – Cassini orbiter releases Huygens probe which will land on Saturn's moon, Titan on January 14, 2005.
 2007 – A tiger escapes from San Francisco Zoo and attacks three people, killing one.
 2009 – Umar Farouk Abdulmutallab attempts a terrorist attack, while on board Northwest Airlines Flight 253.
 2016 - A Russian Defence Ministry Tupolev-154 aircraft crashes into the Black Sea shortly after take-off from Sochi, killing all 92 people on board.

Births