Domestication

Dogs and sheep were among the first animals to be domesticated.

Domestication (from the Latin domesticus: "of the home") is the cultivating or taming of a population of organisms in order to accentuate traits that are desirable to the cultivator or tamer. The desired traits may include a particular physical appearance, behavioral characteristic, individual size, litter size, hair/fur quality or color, growth rate, fecundity, lifespan, ability to use marginal grazing resources, production of certain by-products, and many others. Domesticated organisms may become dependent on humans or human activities, since they sometimes lose their ability to survive in the wild.

Domestication differs from taming in that it may refer not simply to a change in organisms' behaviors or environmental socialization, but also potentially even in their phenotypical expressions and genotypes. The word domestication also is more commonly used to mean a change within whole populations, while taming is more commonly used to mean a change within individuals. Furthermore, taming typically applies only to animals and their becoming habituated to human presence, while domestication is a broader term and can include plants, fungi, and other types of organisms.

Plants domesticated primarily for aesthetic enjoyment in and around the home are usually called house plants or ornamentals, while those domesticated for large-scale food production are generally called crops. A distinction can be made between those domesticated plants that have been deliberately altered or selected for special desirable characteristics (see cultigen) and those plants that are used for human benefit, but are essentially no different from the wild populations of the species. Animals domesticated for home companionship are usually called pets, while those domesticated for food or work are called livestock or farm animals.

Definitions

Domestication

Domestication has been defined as "a sustained multi-generational, mutualistic relationship in which one organism assumes a significant degree of influence over the reproduction and care of another organism in order to secure a more predictable supply of a resource of interest, and through which the partner organism gains advantage over individuals that remain outside this relationship, thereby benefitting and often increasing the fitness of both the domesticator and the target domesticate." This definition recognizes both the biological and the cultural components of the domestication process and the impacts on both humans and the domesticated animals and plants. All past definitions of domestication have included a relationship between humans with plants and animals, but their differences lay in who was considered as the lead partner in the relationship. This new definition recognizes a mutualistic relationship in which both partners gain benefits. Domestication has vastly enhanced the reproductive output of crop plants, livestock, and pets far beyond that of their wild progenitors. Domesticates have provided humans with resources that they could more predictably and securely control, move, and redistribute, which has been the advantage that had fueled a population explosion of the agro-pastoralists and their spread to all corners of the planet.

This biological mutualism is not restricted to humans with domestic crops and livestock but is well-documented in nonhuman species, especially among a number of social insect domesticators and their plant and animal domesticates, for example the ant–fungus mutualism that exists between leafcutter ants and certain fungii.

Domestication syndrome

Domestication syndrome is a term often used to describe the suite of phenotypic traits arising during domestication that distinguish crops from their wild ancestors. The term is also applied to animals and includes increased docility and tameness, coat color changes, reductions in tooth size, changes in craniofacial morphology, alterations in ear and tail form (e.g., floppy ears), more frequent and nonseasonal estrus cycles, alterations in adrenocorticotropic hormone levels, changed concentrations of several neurotransmitters, prolongations in juvenile behavior, and reductions in both total brain size and of particular brain regions.

Background

Charles Darwin was the first to describe the connection between domestication, selection and evolution. Darwin described how the process of domestication can involve both unconscious and methodical elements. Routine human interactions with animals and plants create selection pressures that cause adaptation to human presence, use or cultivation. Deliberate selective breeding has also been used to create desired changes, often after initial domestication. These two forces, unconscious natural selection and methodical selective breeding, may have both played roles in the processes of domestication throughout history. Both have been described from human perspective as processes of artificial selection.

The domestication of wheat provides an example. Wild wheat falls to the ground to reseed itself when ripe, but domesticated wheat stays on the stem for easier harvesting. There is evidence that this change was possible because of a random mutation that happened in the wild populations at the beginning of wheat's cultivation. Wheat with this mutation was harvested more frequently and became the seed for the next crop. Therefore, without realizing, early farmers selected for this mutation, which may otherwise have died out. The result is domesticated wheat, which relies on farmers for its own reproduction and dissemination.

Selective breeding may best explain how continuing processes of domestication often work. Evidence of the power of selective breeding comes from the Farm-Fox Experiment by the Russian scientist, Dmitri K. Belyaev, in the 1950s. His team bred the domesticated silver fox (Vulpes vulpes) and selected the individuals that showed the least fear of humans. Then Belyaev's team selected only those that showed the most positive response to humans. He ended up with a population of grey foxes whose behavior and appearance was significantly changed. They no longer showed any fear of humans and often wagged their tails and licked their human caretakers to show affection. These foxes had floppy ears, smaller skulls, rolled tails and other traits commonly found in dogs. Despite the success of this experiment, it appears that selective breeding cannot always achieve domestication. Attempts to domesticate many kinds of wild animals have been unsuccessful. Although the four species of zebra can interbreed with the horse and the donkey, attempts at domestication have failed. Factors such as temperament, social structure and ability to breed in captivity play a role in determining whether a species can be successfully domesticated. In human history to date, only a few species of large animal have been domesticated. In approximate order of their earliest domestication these are: dog, sheep, goat, pig, ox, yak, reindeer, water buffalo, horse, donkey, llama, alpaca, Bactrian camel and Arabian camel.

Domestication of animals

The zoomass of wild vertebrates is now decreasingly small compared to the biomass of domestic animals, with the calculated biomass of domestic cattle alone being greater than that of all wild mammals. Because the evolution of domestic animals is ongoing, the process of domestication has a beginning but not an end. Various criteria have been established to provide a definition of domestic animals, but all decisions about exactly when an animal can be labelled "domesticated" in the zoological sense are arbitrary, although potentially useful.

Universal features of domesticated animals

Domestication is a fluid and nonlinear process that may start, stop, reverse, or go on unexpected paths with no clear or universal threshold that separates the wild from the domestic. However, there are universal features held in common by all domesticated animals.

Sheep with an ear tag that is part of a national livestock identification system

Behavioral preadaption

Certain animal species, and certain individuals within those species, make better candidates for domestication than others because they exhibit certain behavioral characteristics: (1) the size and organization of their social structure; (2) the degree of selectivity in their choice of mates; (3) the ease and speed with which the parent bonds with young, and the maturity and mobility of the young at birth; (4) the degree of flexibility in diet and habitat tolerance; and (5) responses to humans and new environments, including flight responses and reactivity to external stimuli. Reduced wariness to humans and low reactivity to both humans and other external stimuli are a key pre-adaptation for domestication, and these behaviors are also the primary target of the selective pressures experienced by the animal undergoing domestication. This implies that not all animals can be domesticated, e.g. a wild member of the horse family, the Zebra.

Brain size and function

The sustained selection for lowered reactivity among animal domesticates has resulted in profound changes in brain form and function. The larger the size of the brain to begin with and the greater its degree of folding, the greater the degree of brain-size reduction under domestication. Foxes that had been selectively bred for tameness over 40 years had experienced a significant reduction in cranial height and width and by inference in brain size, which supports the hypothesis that brain-size reduction is an early response to the selective pressure for tameness and lowered reactivity that is the universal feature of animal domestication. The most affected portion of the brain in domestic mammals is the limbic system, which in domestic dogs, pigs, and sheep show a 40% reduction in size compared with their wild species. This portion of the brain regulates endocrine function that influences behaviors such as aggression, wariness, and responses to environmentally induced stress - the key attributes of domestic animals.

Pleiotropy

Pleiotropy occurs when one gene influences two or more seemingly unrelated phenotypic traits. These linked traits include the animal passing through fewer development stages so that as an adult it resembles a juvenile form of its ancestor. Pedomorphosis in development can result in a neotenization of skull morphology, making the animal a more attractive and tractable domestic companion. Lop ears may be be caused by neotonization that essentially freezes the formation of cartilage in the ears at more juvenile stage. Piebald or spotted coat coloration may be caused by a linkage in the biochemical pathways of melanins (involved in coat coloration) and neurotransmitters (dopamine) that help shape behavior and cognition. These linked traits may arise from mutations in a few key regulatory genes. Mutations in only a few regulatory genes can have a major impact on a network of linked genes, resulting in major phenotypic changes. A similar mechanism controls some of the responses of plants to domestication.

Limited reversion

Feral dogs, cats, goats, donkeys, pigs, and ferrets that have lived apart from humans for generations show no sign of regaining the brain mass of their wild progenitors. Dingos have lived apart from humans for thousands of years but still have the same brain size as that of a domestic dog. Feral dogs that actively avoid human contact are still dependent on the human niche for survival and have not reverted to the self-sustaining behaviors of their wolf ancestors.

Other commenters

According to Jared Diamond, animal species must meet six criteria in order to be considered for domestication:

Hereford cattle, domesticated for beef production.

1. Flexible diet – Creatures that are willing to consume a wide variety of food sources and can live off less cumulative food from the food pyramid (such as corn or wheat), particularly food that is not utilized by humans (such as grass and forage) are less expensive to keep in captivity. Carnivores by definition feed primarily or only on flesh, which requires the domesticators to raise additional animals just to feed them, though they may exploit sources of meat not utilized by humans, such as scraps and vermin.
2. Reasonably fast growth rate – Fast maturity rate compared to the human life span allows breeding intervention and makes the animal useful within an acceptable duration of caretaking. Some large animals require many years before they reach a useful size.
3. Ability to be bred in captivity – Creatures that are reluctant to breed when kept in captivity do not produce useful offspring, and instead are limited to capture in their wild state. Creatures such as the panda, antelope and giant forest hog are territorial when breeding and cannot be maintained in crowded enclosures in captivity.
4. Pleasant disposition – Large creatures that are aggressive toward humans are dangerous to keep in captivity. The African buffalo has an unpredictable nature and is highly dangerous to humans; similarly, although the American bison is raised in enclosed ranges in the Western United States, it is much too dangerous to be regarded as truly domesticated. Although similar to the domesticated pig in many ways, Africa's warthog and bushpig are also dangerous in captivity.
5. Temperament which makes it unlikely to panic – A creature with a nervous disposition is difficult to keep in captivity as it may attempt to flee whenever startled. The gazelle is very flighty and it has a powerful leap that allows it to escape an enclosed pen. Some animals, such as the domestic sheep, still have a strong tendency to panic when their flight zone is encroached upon. However, most sheep also show a flocking instinct, whereby they stay close together when pressed. Livestock with such an instinct may be herded by people and dogs.
6. Modifiable social hierarchy – Social creatures whose herds occupy overlapping ranges and recognize a hierarchy of dominance can be raised to recognize a human as the pack leader:
   1. Tapirs and rhinoceroses are solitary and do not tolerate being penned with each other.
   2. Antelope and deer—except for reindeer—are territorial when breeding and live in herds only for the rest of the year.
   3. Bighorn sheep and peccaries have non-hierarchical herd structures and do not follow any definite leader; instead, males fight continuously with each other for mating opportunities.
   4. Musk ox herds, although they have a defined leader, maintain mutually exclusive territories and two herds will fight if kept together.

Cow domestication in North India for milk production.

However, this list is of limited use because it fails to take into account the profound changes that domestication has on a species. While it is true that some animals retain their wild instincts even if born in captivity, e.g. laying hens, pigs and laboratory mice, some factors must be taken into consideration.

Number (5) may not be a prerequisite for domestication, but rather a natural consequence of a species' having been domesticated. In other words, wild animals are naturally timid and flighty because they are constantly faced by predators; domestic animals do not need such a nervous disposition, as they are protected by their human owners. The same holds true for number (4) – aggressive temperament is an adaptation to the danger from predators. A Cape buffalo can kill even an attacking lion, but most modern large domestic animals were descendants of aggressive ancestors. The wild boar, ancestor of the domestic pig, is certainly renowned for its ferocity; other examples include the aurochs (ancestor of modern cattle), horse, Bactrian camels and yaks, all of which are no less dangerous than their undomesticated wild relatives such as zebras and buffalos. Others have argued that the difference lies in the ease with which breeding can improve the dispositions of wild animals, a view supported by the failure to domesticate the kiang and onager. On the other hand, for thousands of years humans have managed to tame dangerous species like bears and cheetahs whose failed domestications had little to do with their aggressiveness.

Number (6), while it does apply to most domesticated species, also has exceptions, most notably in the domestic cat and ferret, which are both descended from strictly solitary wild ancestors but which tolerate and even seek out social interaction in their domestic forms. For example, some feral domestic cats may form colonies around concentrated food sources, and will even share prey and rear kittens communally, while African wildcats remain solitary even in the presence of such food sources. Zoologist Marston Bates devoted a chapter on domestication in his 1960 book The Forest and the Sea, in which he talks a great deal about how domestication alters a species. Dispersal mechanisms tend to disappear for the reason stated above, and additionally, because people provide transportation for them, domestic chickens and turkeys have a greatly reduced ability to fly. Similarly, domestic animals cease to have a definite mating season, so the need to be territorial when mating loses its value, and if some of the males in a herd are castrated, the problem is reduced even further. What he says suggests that the process of domestication can itself make a creature domesticable. Besides, the first steps towards agriculture may have involved hunters keeping young animals, who are always more impressionable than the adults, after killing their mothers.

Another strong factor in deciding whether a species will be considered for domestication is quite simply the availability of more suitable (or, better yet, already domesticated) alternatives. For example, a community that had been introduced to domestication by neighboring peoples will generally find it much more practical, economical, and time saving to import already domesticated species than experiment with wild animals, even if they are of the same species. Generally speaking, the species of animals originally domesticated by early humans in the interconnected landmasses of Eurasia and Africa were far superior, both in working capacity and in food production, than the species found in the other continents, namely the Americas and Oceania.

Domestication pathways

Since 2012, a multi-stage model of animal domestication has been accepted by two groups. The first group proposed that animal domestication proceeded along a continuum of stages from anthropophily, commensalism, control in the wild, control of captive animals, extensive breeding, intensive breeding, and finally to pets in a slow, gradually intensifying relationship between humans and animals.

The second group proposed that there were three major pathways that most animal domesticates followed into domestication: (1) commensals, adapted to a human niche (e.g., dogs, cats, fowl, possibly pigs); (2) prey animals sought for food (e.g., sheep, goats, cattle, water buffalo, yak, pig, reindeer, llama and alpaca); and (3) targeted animals for draft and nonfood resources (e.g., horse, donkey, camel). The beginnings of animal domestication involved a protracted coevolutionary process with multiple stages along different pathways. Humans did not intend to domesticate animals from, or at least they did not envision a domesticated animal resulting from, either the commensal or prey pathways. In both of these cases, humans became entangled with these species as the relationship between them, and the human role in their survival and reproduction, intensified. Although the directed pathway proceeded from capture to taming, the other two pathways are not as goal-oriented and archaeological records suggest that they take place over much longer time frames.

Domestication of plants

See also: History of agriculture, Cultigen, and Horticulture

Farmers with wheat and cattle - Ancient Egyptian art 1,422 YBP

Industrialized wheat harvest - North America today

The earliest human attempts at plant domestication occurred in South-Western Asia. There is early evidence for conscious cultivation and trait selection of plants by pre-Neolithic groups in Syria: grains of rye with domestic traits have been recovered from Epi-Palaeolithic (c. 11,050 BC) contexts at Abu Hureyra in Syria, but this appears to be a localised phenomenon resulting from cultivation of stands of wild rye, rather than a definitive step towards domestication.

By 10,000 BC the bottle gourd (Lagenaria siceraria) plant, used as a container before the advent of ceramic technology, appears to have been domesticated. The domesticated bottle gourd reached the Americas from Asia by 8000 BC, most likely due to the migration of peoples from Asia to America.

Cereal crops were first domesticated around 9000 BC in the Fertile Crescent in the Middle East. The first domesticated crops were generally annuals with large seeds or fruits. These included pulses such as peas and grains such as wheat. The Middle East was especially suited to these species; the dry-summer climate was conducive to the evolution of large-seeded annual plants, and the variety of elevations led to a great variety of species. As domestication took place humans began to move from a hunter-gatherer society to a settled agricultural society. This change would eventually lead, some 4000 to 5000 years later, to the first city states and eventually the rise of civilization itself.

Continued domestication was gradual, a process of trial and error that occurred intermittently. Over time perennials and small trees began to be domesticated including apples and olives. Some plants were not domesticated until recently such as the macadamia nut and the pecan.

In other parts of the world very different species were domesticated. In the Americas squash, maize, beans, and perhaps manioc (also known as cassava) formed the core of the diet. In East Asia millet, rice, and soy were the most important crops. Some areas of the world such as Southern Africa, Australia, California and southern South America never saw local species domesticated.

Domesticated plants often differ from their wild relatives in the way they spread to a more diverse environment and have a wider geographic range; they may also have a different ecological preference; flower and fruit simultaneously; may lack shattering or scattering of seeds, and may have lost their dispersal mechanisms completely; have larger fruits and seeds, and so lower efficiency of dispersal; may have been converted from a perennial to annual; have lost seed dormancy and photoperiodic controls; lack normal pollinating organs; may have a different breeding system; may lack defensive adaptations such as hairs, spines and thorns, protective coverings and sturdiness; may have better palatability and chemical composition, rendering them more likely to be eaten by animals; may be more susceptible to diseases and pests; may develop seedless parthenocarpic fruits; may have undergone selection for double flowers, which may involve conversion of stamens into petals; may have become sexually sterile and therefore only reproduce vegetatively.

Degrees

The distinctions between surviving wild populations and domestic clades can be vague, forming a spectrum of decreasing wildness:

• Wild: These populations experience their full life cycles with little or no deliberate human intervention. Not to be confused with feral, a description of domesticated populations that are not subject to continued selective breeding by humans (see below).
• Raised in captivity (usually captured from the wild, for in zoos, botanical gardens, or human gain): These populations are nurtured by humans, and (among animal species) may or may not be tamed to some extent for safer interaction with facility staff. They usually are not bred under human control, by may be, e.g. in zoos and wildlife preservation facilities, laboratories, and gardens. They remain as a group essentially indistinguishable in appearance or innate behaviour from their wild counterparts. Examples include Asian elephants, the sloth bears and cobras used by showmen in India, Asian black bears (farmed for their bile), and zoo animals, kept in captivity as examples of their species. Zoos and botanical gardens sometimes also exhibit domesticated (including feral) animals and plants such as camels, mustangs, and some orchids.
• Captive-bred (raised commercially): These populations are ranched or farmed in large numbers for food, commodities, the exotic pet trade, and canned hunts. Animal species are often tamed and trained if expected to interact with humans. As a group they are often not substantially altered in appearance or behavior from their wild counterparts, but may be, due to genetic isolation and intentional selective breeding short of full domestication. Examples include the ostrich, various deer, alligator, cricket, honeybee, pearl oyster, raptors used in falconry, ball python, and lion. These populations are sometimes referred to as partially domesticated or semi-domesticated.
• Domesticated: These populations are selectively bred and raised under human control for many generations, and are substantially altered as a group in both appearance and behaviour from their wild progenitor stocks (which in some cases are extinct). Examples include pigs, ferrets, turkeys, canaries, domestic pigeons, budgerigars, goldfish, koi carp, silkworms, dogs, cats, sheep, cattle, chickens, llamas, guinea pigs, mice and rats, horses, goats and silver foxes, among others, including many of the plants humans use as food staples. The domestic category includes standardized breeds and cultivars, as well as less strictly breeding-controlled landraces, and feral populations of both animals and crop plants which are no longer selectively bred but often managed.

This overview does not account for various complicating factors including genetically modified organisms and interspecific hybridization. Many species that are farmed or ranched are now being genetically modified, which alters the organisms as a group in ways that may be unlike traditional domestication. Hybrids can be wild, domesticated, or both: a liger is a hybrid of two wild animals, a mule is a hybrid of two domesticated animals, and a beefalo is a cross between a wild and a domestic animal.

Tame or domesticated

A herd of Pryor Mustangs

A great difference exists between a tamed animal and a domesticated animal. The term domesticated refers to an entire population (often forming a unique subspecies), while the term tame can refer to just one individual within a species or variety. Humans have tamed various animals that have never been truly domesticated. These some that are frequently tamed include elephants, bears and lions. Some wild animals closely related to domesticates are unusually resistant to taming, such as zebras despite their close genetic relationship to horses and donkeys. There is debate over whether certain species have been domesticated or just tamed. Some state that some populations of the elephant have been domesticated, and it has also been argued that the cat has never been fully domesticated. Dividing lines include whether a specimen born to wild parents would differ in appearance or behavior from one born to domesticated parents. For instance, a dog is certainly domesticated because even a wolf (which genetically shares a common ancestor with all dogs) raised from a pup would be very different from a dog, in both appearance and behaviour.

Some languages use the same word for both the "tamed" and "domesticated" concepts, and similarly use a single word for both "wild" and "feral", and/or a single word for both "breed" and "subspecies" or "biological race", distinguishing between the concepts with additional descriptive wording.

Negative aspects

Selection of animals for visible "desirable" traits may make them unfit in other, unseen, ways.

1. REDIRECT Template:POV-statement The consequences for the captive and domesticated animals were reduction in size, piebald color, shorter faces with smaller and fewer teeth, diminished horns, weak muscle ridges, and less genetic variability. Poor joint definition, late fusion of the limb bone epiphyses with the diaphyses, hair changes, greater fat accumulation, smaller brains, simplified behavior patterns, extended immaturity, and more pathology are a few of the defects of domestic animals. All of these changes have been documented in direct observations of the rat in the 19th century, by archaeological evidence, and confirmed by animal breeders in the 20th century. A 2014, a study proposed that many of these features may arise due to mild neural crest deficits that also cause tameness; hence, selectively breeding tame animals also selects for these negative traits.

One side effect of domestication has been zoonotic diseases. For example, cattle have given humanity various viral poxes, measles, and tuberculosis; pigs and ducks have given influenza; and horses have given the rhinoviruses. Humans share over sixty diseases with dogs. Many parasites also have their origins in domestic animals. The advent of domestication resulted in denser human populations which provided ripe conditions for pathogens to reproduce, mutate, spread, and eventually find a new host in humans.

Other negative aspects of domestication have been explored. For example, Paul Shepherd writes "Man substitutes controlled breeding for natural selection; animals are selected for special traits like milk production of passivity, at the expense of overall fitness and naturewide relationships...Though domestication broadens the diversity of forms – that is, increases visible polymorphism – it undermines the crisp demarcations that separate wild species and cripples our recognition of the species as a group. Knowing only domestic animals dulls our understanding of the way in which unity and discontinuity occur as patterns in nature, and substitutes an attention to individuals and breeds. The wide variety of size, color, shape, and form of domestic horses, for example, blurs the distinction among different species of Equus that once were constant and meaningful."

Going further, some anarcho-primitivist authors describe domestication as the process by which previously nomadic human populations shifted towards a sedentary or settled existence through agriculture and animal husbandry. They claim that this kind of domestication demands a totalitarian relationship with both the land and the plants and animals being domesticated. They say that whereas, in a state of wildness, all life shares and competes for resources, domestication destroys this balance. Domesticated landscape (e.g. pastoral lands/agricultural fields and, to a lesser degree, horticulture and gardening) ends the open sharing of resources; where "this was everyone's," it is now "mine." Anarcho-primitivists state that this notion of ownership laid the foundation for social hierarchy as property and power emerged. It also involved the destruction, enslavement, or assimilation of other groups of early people who did not make such a transition.

To primitivists, domestication enslaves both the domesticated species as well as the domesticators. Advances in the fields of psychology, anthropology, and sociology allows humans to quantify and objectify themselves, until they too become commodities.

Dates and places

Early domestication: cow being milked in ancient Egypt.

Since the process of domestication inherently takes many generations over a long period of time, and the spread of breed and husbandry techniques is also slow, it is not meaningful to give a single "date of domestication". However, it is believed that the first attempt at domestication of both animals and plants were made in the Old World by peoples of the Mesolithic Period. The tribes that took part in hunting and gathering wild edible plants, started to make attempts to domesticate dogs, goats, and possibly sheep, which was as early as 9000 BC. However, it was not until the Neolithic Period that primitive agriculture appeared as a form of social activity, and domestication was well under way. The great majority of domesticated animals and plants that still serve humans were selected and developed during the Neolithic Period, a few other examples appeared later. The rabbit for example, was not domesticated until the Middle Ages, while the sugar beet came under cultivation as a sugar-yielding agricultural plant in the 19th century. As recently as the 20th century, mink became an object of agricultural production, and animal breeding programs to produce high-quality fur were started in the same time period.

The methods available to estimate domestication dates introduce further uncertainty, especially when domestication has occurred in the distant past. So the dates given here should be treated with caution; in some cases evidence is scanty and future discoveries may alter the dating significantly.

Dates and places of domestication are mainly estimated by archaeological methods, more precisely archaeozoology. These methods consist of excavating or studying the results of excavation in human prehistorical occupation sites. Animal remains are dated with archaeological methods, the species they belong to is determined, the age at death is also estimated, and if possible the form they had, that is to say a possible domestic form. Various other clues are taken advantage of, such as slaughter or cutting marks. The aim is to determine if they are game or raised animal, and more globally the nature of their relationship with humans. For example, the skeleton of a cat found buried close to humans is a clue that it may have been a pet cat. The age structure of animal remains can also be a clue of husbandry, in which animals were killed at the optimal age.

New technologies and especially mitochondrial DNA, which are simple DNA found in the mitochondria that determine its function in the cell provide an alternative angle of investigation, and make it possible to reestimate the dates of domestication based on research into the genealogical tree of modern domestic animals.

It is admitted for several species that domestication occurred in several places distinctly. For example, research on mitochondrial DNA of the modern cattle Bos taurus supports the archaeological assertions of separate domestication events in Asia and Africa. This research also shows that Bos taurus and Bos indicus haplotypes are all descendants of the extinct wild ox Bos primigenius. However, this does not rule out later crossing inside a species; therefore it appears useless to look for a separate wild ancestor for each domestic breed.

The dog was the first domesticated animal dating 18,000-32,000 years ago, which supports the hypothesis that dog domestication preceded the emergence of agriculture and occurred in the context of European hunter-gatherer cultures. This preceded the domestication of other species by several millennia. In the Neolithic a number of important species such as goats, sheep, pigs and cattle were domesticated, as part of the spread of farming which characterises this period. The goat, sheep and pig in particular were domesticated independently in the Levant and Asia.

There is early evidence of beekeeping, in the form of rock paintings, dating to 13,000 BC.

Recent archaeological evidence from Cyprus indicates domestication of a type of cat by perhaps 9500 BC.

The earliest secure evidence of horse domestication, bit wear on horse molars at Dereivka in Ukraine, dates to around 4000 BC. The unequivocal date of domestication and use as a means of transport is at the Sintashta chariot burials in the southern Urals, c. 2000 BC. Local equivalents and smaller species were domesticated from the 26th century BC.

The availability of both domesticated vegetable and animal species increased suddenly following the voyages of Christopher Columbus and the contact between the Eastern and Western Hemispheres. This is part of what is referred to as the Columbian Exchange.

Approximate dates and locations of original domestication

Main article: List of domesticated animals

Species	Date	Location
Dog (Canis lupus familiaris)	prior to 33000 BC	Eurasia
Sheep (Ovis orientalis aries)	between 11000 BC and 9000 BC	Southwest Asia
Pig (Sus scrofa domestica)	9000 BC	Near East, China
Goat (Capra aegagrus hircus)	10000 BC	Near East
Cattle (Bos primigenius taurus)	8000 BC	India, Middle East, and North Africa
Cat (Felis catus)	7500 BC	Cyprus and Near East
Chicken (Gallus gallus domesticus)	6000 BC	India and Southeast Asia
Guinea pig (Cavia porcellus)	5000 BC	Peru
Donkey (Equus africanus asinus)	5000 BC	Egypt
Domesticated duck (Anas platyrhynchos domesticus)	4000 BC	China
Water buffalo (Bubalus bubalis)	4000 BC	India, China
Horse (Equus ferus caballus)	3500 BC	Kazakhstan
Dromedary (Camelus dromedarius)	4000 BC	Arabia
Llama (Lama glama)	6000 BC	Peru
Silkworm (Bombyx mori)	3000 BC	China
Reindeer (Rangifer tarandus)	3000 BC	Russia
Rock pigeon (Columba livia)	3000 BC	Mediterranean Basin
Goose (Anser anser domesticus)	3000 BC	Egypt
Bactrian camel (Camelus bactrianus)	2500 BC	Central Asia, Afghanistan
Yak (Bos grunniens)	2500 BC	Tibet
Banteng (Bos javanicus)	Unknown	Southeast Asia
Gayal (Bos gaurus frontalis)	Unknown	Southeast Asia
Alpaca (Vicugna pacos)	1500 BC	Peru
Ferret (Mustela putorius furo)	1500 BC	Europe
Muscovy duck (Cairina momelanotus)	Unknown	South America
Guineafowl	Unknown	Africa
Common carp (Cyprinus carpio)	Unknown	East Asia
Domesticated turkey (Meleagris gallopavo)	500 BC	Mexico
Goldfish (Carassius auratus auratus)	Unknown	China
European rabbit (Oryctolagus cuniculus)	AD 600	Europe

Additional domestications:

Species	Date	Location
Zebu (Bos primigenius indicus)	8000 BC	India
Honey bee	4000 BC	Multiple places
Asian elephant (Elephas maximus) (endangered)	2000 BC	Indus Valley civilization
Fallow deer (Dama dama)	1000 BC	Mediterranean Basin
Indian peafowl (Pavo cristatus)	500 BC	India
Barbary dove (Streptopelia risoria)	500 BC	North Africa
Japanese quail (Coturnix japonica)	1100–1900	Japan
Mandarin duck (Aix galericulata)	Unknown	China
Mute swan (Cygnus olor)	1000–1500	Europe
Canary (Serinus canaria domestica)	1600	Canary Islands, Europe

Modern instances

Species	Date	Location
Fancy rat (Rattus norvegicus)	1800s	UK
Fox (Vulpes vulpes)	1800s	Europe
European mink (Mustela lutreola)	1800s	Europe
Budgerigar (Melopsittacus undulatus)	1850s	Australia
Cockatiel (Nymphicus hollandicus)	1870s	Australia
Zebra finch (Taeniopygia guttata)	1900s	Australia
Hamster (Mesocricetus auratus)	1930s	United States
Silver fox	1950s	Soviet Union
Muskox (Ovibos moschatus)	1960s	United States
Corn snake (Pantherophis guttatus guttatus)	1960s	United States
Ball python (Python regius)	1960s	Africa
Madagascar hissing cockroach (Gromphadorhina portentosa)	1960s	Madagascar
Red deer (Cervus elaphus)	1970s	New Zealand
Hedgehog (Atelerix albiventris)	1980s	United States
Sugar glider (Petaurus breviceps)	1980s	Australia
Skunk (Mephitis mephitis)	1980s	United States
Capybara (Hydrochoerus hydrochaeris)	1990s	United States

Researchers at the Max Planck institute in Germany are attempting to find a genetic basis for the processes of taming and domestication. They have obtained two strains of grey rats which were bred by Dmitry Konstantinovich Belyaev at the Institute of Cytology and Genetics in Novosibirsk, Russia, research which was later continued by Irina Plyusnina. One strain had been selected for aggressiveness while the other had been selected for tameness, mimicking the process by which neolithic farmers are thought to have first domesticated animals. A similar experiment studying silver foxes has been ongoing at the same institute since 1959. Richard Wrangham of Harvard suggests that similar genes could be involved in human self-domestication.

Former instances

Some species are said to have been domesticated, but are not any more, either because they have totally disappeared, or since their domestic form no longer exists. Examples include the jaguarundi, the kakapo, the ringtail, caracal, and Bos aegyptiacus.

Hybrid domestic animals

• Alpaca: DNA evidence shows that alpacas are a llama/vicuña hybrid
• Beefalo
• Bengal cat
• Cama (animal)
• Chausie
• Coydog
• Dzo
• Domesticated hedgehog: A cross between the Algerian hedgehog and the four-toed hedgehog.
• Sheep-goat hybrid
• Hinny
• Huarizo
• Iron Age pig
• Mule
• Savannah (cat)
• Wolfdog
• Yakalo
• Zeedonk
• Zorse
• Zony
• Zubron

Genetic pollution

Main article: Genetic pollution

Animals of domestic origin and feral ones sometimes can produce fertile hybrids with native, wild animals which leads to genetic pollution in the naturally evolved wild gene pools, many times threatening rare species with extinction. Cases include the mallard duck, wildcat, wild boar, the rock dove or pigeon, the red junglefowl (Gallus gallus) (ancestor of all chickens), carp, and more recently salmon. Another example is the dingo, itself an early feral dog, which hybridizes with dogs of European origin. On the other hand, genetic pollution seems not to be noticed for rabbits. There is much debate over the degree to which feral hybridization compromises the purity of a wild species. In the case of the mallard, for example, some claim there are no populations which are completely free of any domestic ancestor.

See also

• Animal husbandry
• Anthrozoology
• Columbian Exchange
• Domesticated silver fox
• Domestication of the horse
• Domestication theory
• Experimental evolution
• Genetic engineering
• Genetic erosion
• Genetic pollution
• Genomics of domestication
• History of plant breeding
• Horticulture
• Lion taming
• List of domesticated animals
• List of domesticated fungi and microorganisms
• List of domesticated plants
• Marker assisted selection
• Selective breeding
• Self-domestication
• Timeline of agriculture and food technology
• Ethnozoology

Bibliography

• Darwin, Charles. The Variation of Animals and Plants under Domestication, 1868.
• Diamond, Jared. Guns, germs and steel. A short history of everybody for the last 13,000 years, 1997.
• Hobgood-Oster, Laura. A Dog's History of the World: Canines and the Domestication of Humans, 2014.
• Ryden, Hope. Out of the Wild: The Story of Domesticated Animals, 1995.

Further reading

• Halcrow, S. E., Harris, N. J., Tayles, N., Ikehara-Quebral, R. and Pietrusewsky, M. (2013), From the mouths of babes: Dental caries in infants and children and the intensification of agriculture in mainland Southeast Asia. Am. J. Phys. Anthropol., 150: 409–420. doi: 10.1002/ajpa.22215
• Hayden, B. (2003). Were luxury foods the first domesticates? Ethnoarchaeological perspectives from Southeast Asia. World Archaeology, 34(3), 458-469.

External links

• Crop Wild Relative Inventory and Gap Analysis: reliable information source on where and what to conserve ex-situ, for crop genepools of global importance
• Discussion of animal domestication
• Guns, Germs and Steel by Jared Diamond (ISBN 0-393-03891-2)
• News story about an early domesticated cat find
• Belyaev experiment with the domestic fox
• Use of Domestic Animals in Zoo Education
• The Initial Domestication of Cucurbita pepo in the Americas 10,000 Years Ago
• Cattle domestication diagram
• Major topic "domestication": free full-text articles (more than 100 plus reviews) in National Library of Medicine
• Why don't we ride zebras? an online children's film about animal domestication
• Isidro A. T. Savillo and Villaluz, Elizabeth A. 2013 this introduces a proposed Domesticity Scale for Wild Birds