Domestication
Domestication (from Latin domesticus) or taming - is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. A defining characteristic of domestication is artificial selection by humans.
Humans have brought these populations under their control and care for a wide range of reasons: to produce food or valuable commodities (such as wool, cotton, or silk), for help with various types of work (such as transportation, protection, and warfare), scientific research, or simply to enjoy as companions.
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.
Humans have brought these populations under their control and care for a wide range of reasons: to produce food or valuable commodities (such as wool, cotton, or silk), for help with various types of work (such as transportation, protection, and warfare), scientific research, or simply to enjoy as companions.
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 and those domesticated plants that are essentially no different from their wild counterparts (assuming domestication does not necessarily imply physical modification). Animals domesticated for home companionship are usually called pets while those domesticated for food or work are called livestock or farm animals.
Charles Darwin describes 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 as species adjust 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 man's perspective as processes of artificial selection.
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 man's 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 critical change came about as a result of a random mutation near the beginning of wheat's cultivation. Wheat with this mutation was harvested and became the seed for the next crop. Therefore, without realizing, early farmers selected for this mutation, which would otherwise have died out. The result is domesticated wheat, which relies on farmers for its own reproduction and dissemination.
There is evidence that this critical change came about as a result of a random mutation near the beginning of wheat's cultivation. Wheat with this mutation was harvested and became the seed for the next crop. Therefore, without realizing, early farmers selected for this mutation, which would otherwise have died out. The result is domesticated wheat, which relies on farmers for its own reproduction and dissemination.
Mutation is not the only way in which natural and artificial selection operate. Darwin describes how natural variations in individual plants and animals also support the selection of new traits. It is speculated that tamer than average wolves, less wary of humans, selected themselves as domestic dogs over many generations.
These wolves were able to thrive by following humans to scavenge for food near camp fires and garbage dumps. Eventually a symbiotic relationship developed between people and these proto-dogs. The dogs fed on human food scraps, and humans found that dogs could warn them of approaching dangers, help with hunting, act as pets, provide warmth, or supplement their food supply.
As this relationship evolved, humans eventually began to keep these self-tamed wolves and breed from them the types of dogs that we have today.
These wolves were able to thrive by following humans to scavenge for food near camp fires and garbage dumps. Eventually a symbiotic relationship developed between people and these proto-dogs. The dogs fed on human food scraps, and humans found that dogs could warn them of approaching dangers, help with hunting, act as pets, provide warmth, or supplement their food supply.
As this relationship evolved, humans eventually began to keep these self-tamed wolves and breed from them the types of dogs that we have today.
In recent times, selective breeding may best explain how continuing processes of domestication often work. Some of the best-known evidence of the power of selective breeding comes from an experiment by Russian scientist, Dmitri K. Belyaev, in the 1950s. His team spent many years breeding the Silver Fox (Vulpes vulpes) and selecting only those individuals that showed the least fear of humans.
Eventually, Belyaev's team selected only those that showed the most positive response to humans. He ended up with a population of grey-coloured 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. Fascinatingly, these foxes had floppy ears, smaller skulls, rolled tails and other traits commonly found in dogs.
Eventually, Belyaev's team selected only those that showed the most positive response to humans. He ended up with a population of grey-coloured 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. Fascinatingly, 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. The zebra is one example. Despite the fact that four species of zebra can interbreed with and are part of the same genus as 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.
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.
According to evolutionary biologist Jared Diamond, animal species must meet six criteria in order to be considered for domestication:
- 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 animal tissue, which requires the expenditure of many animals, though they may exploit sources of meat not utilized by humans, such as scraps and vermin.
- 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. Large animals such as elephants require many years before they reach a useful size.
- 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.
- 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 US West, it is much too dangerous to be regarded as truly domesticated. Although similar to the domesticated pig in many ways, the American peccary and Africa's warthog and bushpig are also dangerous in captivity.
- 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.
- Modifiable social hierarchy — Social creatures that recognize a hierarchy of dominance can be raised to recognize a human as the pack leader.
Study of the Molecular Basis of Tame and Aggressive Behavior in the Silver Fox Model International Collaborative Study between The James A. Baker Institute for Animal Health, Cornell University, USA, The Institute of Cytology and Genetics, Russian Academy of Sciences, Russia, and Department of Biology, University of Utah, USA.
Behavior of all foxes included in the study is tested by the standardized scheme. Video demonstrate behavior of foxes from aggressive and tame populations in the standard test.
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The standard test includes five steps:
1- observer approaching fox cage; 2- observer stays near closed cage; 3- observer is near open cage but does not initiate tactile contact; 4- tactile contact; 5- observer stays near closed cage. Each step (except step one) is 1 minute long (in the movie the length of each step was decreased about two times). Fox behavior during the entire test is videotaped to preserve a permanent record, and to allow subsequent detailed analyses of fox behavior during the test. Each fox is tested at least twice at several age points by the same observer. |
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These experiments and studies are ongoing to this day - one wonders why - after more than 50 years of studies, the results should be detectable and there is no reason to continue to force wild or tamed animals to live in cramped cages, it is animal cruelty - But this farm may still works as a fur farm?
History of the domestication of animals
Hunting species: 20,000-10,000 years ago During the most recent ice age, from about 20,000 years ago (see Ice Ages), large mammals such as bison roam on the sub-arctic tundra of Europe and Asia.
They are preyed upon by two groups of hunters, both much smaller and weaker than themselves - but both with a sufficiently developed social system to enable them to hunt and kill in packs.
These hunters are humans and wolves - The typical pack of wolves and of humans is surprisingly similar. It is family-based, led by a dominant male whose female partner is likely to have an authority second only to his.
They are preyed upon by two groups of hunters, both much smaller and weaker than themselves - but both with a sufficiently developed social system to enable them to hunt and kill in packs.
These hunters are humans and wolves - The typical pack of wolves and of humans is surprisingly similar. It is family-based, led by a dominant male whose female partner is likely to have an authority second only to his.
Members of the group are friendly to each other but deeply suspicious of outsiders. All members (not just the parents) are protective of the newly born and the young. Both species are good at interpreting the moods of others in the group, whether through facial expression or other forms of body language.
Legend acknowledges these shared characteristics in stories of children suckled by wolves. The other side of the same coin, in real life, means that wolf cubs adapt easily to life among humans.
Legend acknowledges these shared characteristics in stories of children suckled by wolves. The other side of the same coin, in real life, means that wolf cubs adapt easily to life among humans.
For mutual benefit - Humans and wolves are competing for the same prey, but there are advantages for both in teaming up. For the wolf, human ingenuity and the use of weapons mean a share in a greater number of kills - and perhaps even an occasional taste of larger victims, such as mammoth. For humans, the wolf's speed and ferocity is equivalent to a new weapon.
The partnership is natural. So, undoubtedly, is how it first comes about. People love to nurture any abandoned young animal, and a wolf cub is well adapted to learn the rules of a hierarchical human society (in which its place will be low). From this partnership all dogs derive. Unbelievable though it seems, every single breed of dog is descended from wolves.
The partnership is natural. So, undoubtedly, is how it first comes about. People love to nurture any abandoned young animal, and a wolf cub is well adapted to learn the rules of a hierarchical human society (in which its place will be low). From this partnership all dogs derive. Unbelievable though it seems, every single breed of dog is descended from wolves.
For a species to become domesticated, it must be willing to breed in man's company. 'Breed in captivity', the more usual phrase, implies a simple case of exploitation. The reality is more complex. In terms of survival, those species which have developed a relationship with man have far outstripped their wild cousins.
The most numerous large mammals, apart from humans, are cows, sheep, goats, pigs, horses and dogs. Domestic cats easily outnumber their wild equivalents, as do chickens and turkeys. The domestication of animals is based on an ancient contract, with benefits on both sides, between man and the ancestors of the breeds familiar to us today.
The most numerous large mammals, apart from humans, are cows, sheep, goats, pigs, horses and dogs. Domestic cats easily outnumber their wild equivalents, as do chickens and turkeys. The domestication of animals is based on an ancient contract, with benefits on both sides, between man and the ancestors of the breeds familiar to us today.
Dogs: from 12,000 years ago - The earliest known evidence of a domesticated dog is a jawbone found in a cave in Iraq and dated to about 12,000 years ago. It differs from a wolf in that it has been bred to have a smaller jaw and teeth.
Selective breeding affects a species quite rapidly, and is a natural process for man to initiate - probably at first by accident rather than intention. A particular puppy in a litter is favoured because it has an attractive coat, barks well, is unusually friendly or obedient, noticeably large or small. This is the dog which is kept and in its turn has puppies. Its desirable characteristics become perpetuated.
Selective breeding affects a species quite rapidly, and is a natural process for man to initiate - probably at first by accident rather than intention. A particular puppy in a litter is favoured because it has an attractive coat, barks well, is unusually friendly or obedient, noticeably large or small. This is the dog which is kept and in its turn has puppies. Its desirable characteristics become perpetuated.
Scientists disagree on when the first domesticated dog occurred and how to define domestication. It has been found a skull (30.000 years old) which shows a shift towards wolves' heads, but it does not say that these changes have anything to human influence to do. Evidence that humans domesticated wolves to dogs can be seen later, and also that there is evidence of burial remains, in which man and dog living together.
Images in Egyptian paintings, Assyrian sculptures and Roman mosaics reveal that by the time of these civilizations there are many different shapes and sizes of dog. To use the word 'breed' may be anachronistic, though there is evidence that a dog very like the present-day Pekingese (almost as far as one can get from a wolf) exists in China by the 1st century AD.
By that time Roman ladies also have lap dogs; their warmth is believed to be a cure for stomach ache.
Images in Egyptian paintings, Assyrian sculptures and Roman mosaics reveal that by the time of these civilizations there are many different shapes and sizes of dog. To use the word 'breed' may be anachronistic, though there is evidence that a dog very like the present-day Pekingese (almost as far as one can get from a wolf) exists in China by the 1st century AD.
By that time Roman ladies also have lap dogs; their warmth is believed to be a cure for stomach ache.
A Roman writer of the period gives similarly practical reasons for selecting the colour of a dog: shepherds' dogs should be white (to distinguish them from wolves in the dark) but a farmyard dog should have a black coat (to frighten thieves)s.
Sheep and goats, cattle and pigs: 9000-7000 BC The first animals known to have been domesticated as a source of food are sheep in the Middle East. The proof is the high proportion of bones of one-year-old sheep discarded in a settlement at Shanidar, in what is now northern Iraq.
Goats follow soon after, and these two become the standard animals of the nomadic pastoralists - tribes which move all year long with their flocks, guided by the availability of fresh grass. Cattle and pigs, associated more with settled communities, are domesticated slightly later - but probably not long after 7000 BC. The ox may first have been bred by humans in western Asia. The pig is probably first domesticated in China.
Goats follow soon after, and these two become the standard animals of the nomadic pastoralists - tribes which move all year long with their flocks, guided by the availability of fresh grass. Cattle and pigs, associated more with settled communities, are domesticated slightly later - but probably not long after 7000 BC. The ox may first have been bred by humans in western Asia. The pig is probably first domesticated in China.
The first reason for herding sheep and goats, or keeping cattle and pigs in the village, is to secure a regular supply of fresh meat. The hunter is dependent on the luck of the chase; if more animals are killed than can be immediately consumed, meals from the surplus will be increasingly unpleasant as the days go by. The herdsman, by contrast, has a living larder always to hand and a supply of dairy products as well.
These animals also provide for almost every other need of neolithic man. While they are alive, they produce dung to manure the crops. When they are dead, leather and wool for garments; horn and bone for sharp points, of needles or arrows; fat for tallow candles; hooves for glue.
These animals also provide for almost every other need of neolithic man. While they are alive, they produce dung to manure the crops. When they are dead, leather and wool for garments; horn and bone for sharp points, of needles or arrows; fat for tallow candles; hooves for glue.
Draught animals: from 4000 BC - Of the four basic farm animals, cattle represent the most significant development in village life. Not only does the cow provide much more milk than its own offspring require, but the brute strength of the ox is an unprecedented addition to man's muscle power.
From about 4000 BC oxen are harnessed and put to work. They drag sledges and, somewhat later, ploughs and wheeled wagons (an almost simultaneous innovation in the Middle East and in Europe). The plough immeasurably increases the crop of wheat or rice. The wagon enables it to be brought home from more distant fields.
India and southeast Asia use another version of the domesticated ox, well adapted to hot wet conditions - the water buffalo.
From about 4000 BC oxen are harnessed and put to work. They drag sledges and, somewhat later, ploughs and wheeled wagons (an almost simultaneous innovation in the Middle East and in Europe). The plough immeasurably increases the crop of wheat or rice. The wagon enables it to be brought home from more distant fields.
India and southeast Asia use another version of the domesticated ox, well adapted to hot wet conditions - the water buffalo.
Whether dragging a plough-like tool through a flooded field or hauling a cart on a dry track, the buffalo is ideally suited to the role of a farm animal in rice-growing areas. Like other members of the ox family, it also provides a good supply of milk.
The buffalo is first domesticated somewhere in the near-tropical regions of Asia. Precisely where or when is not known, but buffaloes feature as domestic animals on the seals of the Indus civilization.
The buffalo is first domesticated somewhere in the near-tropical regions of Asia. Precisely where or when is not known, but buffaloes feature as domestic animals on the seals of the Indus civilization.
Cats: from before 3000 BC - Apart from dogs, cats are the only domesticated animals to dwell indoors with humans. It is also the only one which is solitary in the wild, as opposed to living in packs, herds or flocks. As a result the cat has been able to take what it wants from man (food, shelter, play) and to pay its dues in return (pest control) without losing contact with its original identity.
Cats have remained closer than other domesticated animals to their wild cousins, partly because it is so difficult to control their breeding. And they are more able than any other to fend for themselves, in the country or even in a city, if human support is withdrawn.
Cats have remained closer than other domesticated animals to their wild cousins, partly because it is so difficult to control their breeding. And they are more able than any other to fend for themselves, in the country or even in a city, if human support is withdrawn.
It is not known when cats are first domesticated. But by the time of the earliest civilization they have already acquired in the human mind a characteristic which they have never lost - the quality of mystery.
In the temples of Egypt cats are sacred animals, and are mummified in their millions. In folk stories of all nations a cat is the natural companion for people who possess an alarming second sight, such as witches.
In the temples of Egypt cats are sacred animals, and are mummified in their millions. In folk stories of all nations a cat is the natural companion for people who possess an alarming second sight, such as witches.
Horses: 3000 BC - Humans acquire their most important single ally from the animal kingdom when they domesticate the horse, in about 3000 BC.
Wild horses of various kinds have spread throughout most of the world by the time human history begins. Their bones feature among the remains of early human meals, and they appear in cave paintings with other animals of the chase.
Some of their earliest fossil remains have been found in America, but after arriving across the Bering Land Bridge they become extinct in that continent. They are reintroduced by European colonists in the 16th century.
Wild horses of various kinds have spread throughout most of the world by the time human history begins. Their bones feature among the remains of early human meals, and they appear in cave paintings with other animals of the chase.
Some of their earliest fossil remains have been found in America, but after arriving across the Bering Land Bridge they become extinct in that continent. They are reintroduced by European colonists in the 16th century.
A natural habitat of the wild horse is the steppes of central Asia. Here, with its ability to move fast and far, it can gallop out of harm's way and make the most of scarce grazing. And here, some 5000 years ago, humans first capture, tame and breed the horse. The original purpose, as with cattle, is to acquire a reliable source of meat and subsequently milk. But then, in a crucial development, tribesmen discover that they have at their disposal a means of transport.
With a horse beneath him, man's ability to move is improved out of all recognition. The next comparable moment in the story of human speed does not arrive for another 5000 years - with steam trains.
The first domesticated horses are of a size which we would describe as ponies. Horses of this kind were still living in the wild in Mongolia until quite recent times. Discovered there in the 1870s, and named Przewalski's horse, they survive now only in zoos.
The entire range of horses known to us, from the mighty carthorse down to the smallest ponies, is the result of human breeding. Other wild breeds, now extinct, have been added to the stock. One such example is the tarpan, which was the native breed in Europe.
The first domesticated horses are of a size which we would describe as ponies. Horses of this kind were still living in the wild in Mongolia until quite recent times. Discovered there in the 1870s, and named Przewalski's horse, they survive now only in zoos.
The entire range of horses known to us, from the mighty carthorse down to the smallest ponies, is the result of human breeding. Other wild breeds, now extinct, have been added to the stock. One such example is the tarpan, which was the native breed in Europe.
Asses: 3000 BC - At much the same time as the wild horse is being domesticated in the region of the Black Sea and the Caspian, its cousin the ass or donkey (a member of the same equus family) is tamed in Egypt.
At this time the donkey appears to have roamed wild in northeast Africa and up through the Fertile Crescent into Mesopotamia. So both horse and the ass, from north and from south, become available to two of the earliest civilizations - in Mesopotamia and Egypt.
At this time the donkey appears to have roamed wild in northeast Africa and up through the Fertile Crescent into Mesopotamia. So both horse and the ass, from north and from south, become available to two of the earliest civilizations - in Mesopotamia and Egypt.
Silk moths: 3000 BC - In China an indigenous silk moth is co-opted for man's purposes. Bombyx mori is still the only insect to have been fully domesticated (in the sense that, unlike the bee, it cannot live in the wild and is not known in a wild form).
The silk moth has lost the power to fly; its caterpillar can find no mulberry leaves for itself. The species exists, and survives, only because humans like silk.
The earliest known silk from bombyx mori was found in a bamboo basket unearthed by archaeologists in China. Other pieces in the same basket were from wild silkworms. The fragments date from between 2850 and 2650 BC.
The silk moth has lost the power to fly; its caterpillar can find no mulberry leaves for itself. The species exists, and survives, only because humans like silk.
The earliest known silk from bombyx mori was found in a bamboo basket unearthed by archaeologists in China. Other pieces in the same basket were from wild silkworms. The fragments date from between 2850 and 2650 BC.
Camels: 3000-1500 BC - As beasts of burden and transport, camels occupy an important place alongside horses and donkeys. Two small members of the camel family, the llama and the alpaca of south America, are domesticated first - probably before 3000 BC.
At that time both species appear to have been on the verge of extinction. Domestication by the American Indians saves them. Neither the llama nor the alpaca exists now in the wild.
The larger of the two, the llama, is primarily a beast of burden, while the shaggy alpaca is valuable for its wool. Neither animal is strong enough to pull a plough or drag a cart - two important steps in the story of civilization which are denied to the early Americans.
At that time both species appear to have been on the verge of extinction. Domestication by the American Indians saves them. Neither the llama nor the alpaca exists now in the wild.
The larger of the two, the llama, is primarily a beast of burden, while the shaggy alpaca is valuable for its wool. Neither animal is strong enough to pull a plough or drag a cart - two important steps in the story of civilization which are denied to the early Americans.
Poultry and pigeons: 2000 BC - The red jungle fowl, a member of the pheasant family, lives in the forests and bamboo jungles of India and southeast Asia.
The male makes an impressive crowing sound and is dignified by a comb on his head and wattles under his beak. Jungle fowl of this kind are captured and kept for their eggs and their flesh by about 2000 BC in Asia. It is thought that all domestic poultry in the world today are descended from this one species.
At much the same period, in Egypt, pigeons are first persuaded to live and breed in the proximity of humans - again as a reliable source of protein. But some 3000 years later it is discovered that they have an extra and unusual talent. Some of them can be trained to fly home.
The male makes an impressive crowing sound and is dignified by a comb on his head and wattles under his beak. Jungle fowl of this kind are captured and kept for their eggs and their flesh by about 2000 BC in Asia. It is thought that all domestic poultry in the world today are descended from this one species.
At much the same period, in Egypt, pigeons are first persuaded to live and breed in the proximity of humans - again as a reliable source of protein. But some 3000 years later it is discovered that they have an extra and unusual talent. Some of them can be trained to fly home.
Elephants: 2000 BC - India is the region where elephants are first tamed, during the Indus civilization. The two species of elephant are at this time widespread - the Indian elephant throughout temperate Asia as far west as Syria, and the African elephant in regions north and south of the Sahara.
It is not known when elephants are first trained to take part in war, but by the 3rd century BC they are a valuable military force in both India and north Africa. An ability to learn tricks also makes the elephant a performing animal, popular in the arena of the Roman circus.
It is not known when elephants are first trained to take part in war, but by the 3rd century BC they are a valuable military force in both India and north Africa. An ability to learn tricks also makes the elephant a performing animal, popular in the arena of the Roman circus.
The honey of the bee: before the 6th century BC - No doubt hunter-gatherers, when they find the honey of bees in a hollow tree, often risk a sting for the pleasure of sweetness.
The story of beekeeping can be described as the search for safer and more convenient ways of robbing a bees' nest.
The turning point in the domestication of the bee is the discovery that a swarm of bees can be coaxed into a specific nest - one designed by man for his own convenience in collecting the honey, and with it the useful substance of beeswax.
The story of beekeeping can be described as the search for safer and more convenient ways of robbing a bees' nest.
The turning point in the domestication of the bee is the discovery that a swarm of bees can be coaxed into a specific nest - one designed by man for his own convenience in collecting the honey, and with it the useful substance of beeswax.
It is not known when the beehive is first developed, but the Greeks in classical times use a design which for centuries remains standard in much of Europe.
Known as a skep, it is a dome constructed from a continuous coil of woven straw - looking much like an upturned basket. It stands on a wooden platform with a hole in, through which the bees enter.
The disadvantage of such a system is that the removal of the honey involves disturbing the nest of the bees. From the 17th century, when wooden hives come into use, extra chambers are added for the collection of honey. But the major improvement in beekeeping techniques is the achievement of a 19th-century clergyman, L.L. Langstroth.
Known as a skep, it is a dome constructed from a continuous coil of woven straw - looking much like an upturned basket. It stands on a wooden platform with a hole in, through which the bees enter.
The disadvantage of such a system is that the removal of the honey involves disturbing the nest of the bees. From the 17th century, when wooden hives come into use, extra chambers are added for the collection of honey. But the major improvement in beekeeping techniques is the achievement of a 19th-century clergyman, L.L. Langstroth.
Rabbits: from the 1st century BC - Since Roman times, if not before, people have encouraged rabbits to breed in captivity for the sake of their meat, and have then regretted doing so because of the animal's ability to burrow to freedom and eat the crops.
The only safe place to keep rabbits is on an island. (Almost every island of the world has rabbits on, brought by humans to establish a living larder for passing ships).
Rabbits are inaccessible in their burrows, so man domesticates a species of polecat (in the form of the ferret) to flush them out. As early as the 1st century AD Pliny describes the use of ferrets in the Balearic islands, as the inhabitants struggle to control the rabbits.
The only safe place to keep rabbits is on an island. (Almost every island of the world has rabbits on, brought by humans to establish a living larder for passing ships).
Rabbits are inaccessible in their burrows, so man domesticates a species of polecat (in the form of the ferret) to flush them out. As early as the 1st century AD Pliny describes the use of ferrets in the Balearic islands, as the inhabitants struggle to control the rabbits.
The turkey: from the 14th century - The turkey is indigenous to central and north America. It is kept as a domestic fowl by the Aztecs in Mexico from the 14th century, and no doubt has been domesticated considerably earlier by their predecessors.
Turkeys are brought to Europe by the Spanish in the early 16th century. They become popular throughout the continent, and in the 17th century they are taken back across the Atlantic by English settlers.
Interbred with wild turkeys of north America, develop into the breeds known there today.
Turkeys are brought to Europe by the Spanish in the early 16th century. They become popular throughout the continent, and in the 17th century they are taken back across the Atlantic by English settlers.
Interbred with wild turkeys of north America, develop into the breeds known there today.
The bee space: AD 1851 - An American clergyman, the Rev. L.L. Langstroth, puts to practical use the very precise habits of bees. Other beekeepers in the 19th century have begun putting into the hives removable frames, in which the bees will build their honeycombs, but the bees clog the spaces up with wax and honey.
In 1851 Langstroth discovers that if the frames are an exact distance apart (a little more than a quarter of an inch), the workers will keep each honey-filled frame neat and separate. A gap which is larger or smaller does not have the same effect. The 'bee space' becomes an established principle, and the Langstroth hive is still the type used by beekeepers today.
In 1851 Langstroth discovers that if the frames are an exact distance apart (a little more than a quarter of an inch), the workers will keep each honey-filled frame neat and separate. A gap which is larger or smaller does not have the same effect. The 'bee space' becomes an established principle, and the Langstroth hive is still the type used by beekeepers today.
The ostrich: 19th - 20th century - In addition to the standard domesticated animals, many others have been kept or are now kept by humans for a wide range of purposes.
A good example is the ostrich. In the late 19th-century the fashion for ostrich feathers, in hats or fans, causes farmers to domesticate and breed this largest of birds. In the late 20th-century there is more interest in it for its meat.
A good example is the ostrich. In the late 19th-century the fashion for ostrich feathers, in hats or fans, causes farmers to domesticate and breed this largest of birds. In the late 20th-century there is more interest in it for its meat.
The hamster: 1930 - In the ongoing story of domestication, the remarkable case of the golden hamster is a good detail for a closing chapter. In 1930 a female hamster with twelve young is captured at Aleppo in Syria.
Taken to the laboratory at the Hebrew university in Jerusalem, they are bred for use in experiments. Each female has several litters a year, so the numbers rapidly grow.
Other laboratories secure their own supply from Jerusalem. Then somebody notices that this little animal - chubby, with puffed out cheeks and soft fur - has considerable charm as a pet for children.
Half a century on the golden hamster is a common domesticated animal. Every single hamster in captivity descends from that first Syrian litter.
Source: Wikipedia and Historyworld
Taken to the laboratory at the Hebrew university in Jerusalem, they are bred for use in experiments. Each female has several litters a year, so the numbers rapidly grow.
Other laboratories secure their own supply from Jerusalem. Then somebody notices that this little animal - chubby, with puffed out cheeks and soft fur - has considerable charm as a pet for children.
Half a century on the golden hamster is a common domesticated animal. Every single hamster in captivity descends from that first Syrian litter.
Source: Wikipedia and Historyworld
Experimental evolution
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In evolutionary and experimental biology, the field of experimental evolution is concerned with testing hypotheses and theories of evolution by use of controlled experiments.
Evolution may be observed in the laboratory as populations adapt to new environmental conditions and/or change by such stochastic processes as random genetic drift. With modern molecular tools, it is possible to pinpoint the mutations that selection acts upon, what brought about the adaptations, and to find out how exactly these mutations work. |
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Because of the large number of generations required for adaptation to occur, evolution experiments are typically carried out with microorganisms such as bacteria, yeast or viruses.
However, laboratory studies with foxes and with rodents have shown that notable adaptations can occur within as few as 10-20 generations and experiments with wild guppies have observed adaptations within comparable numbers of generations. Evolution experiments throughout human history - Unwittingly, humans have carried out evolution experiments for as long as they have been domesticating plants and animals. Selective breeding of plants and animals has led to varieties that differ dramatically from their original wild-type ancestors. |
Examples are the cabbage varieties, maize, or the large number of different dog breeds. The power of human breeding to create varieties with extreme differences from a single species was already recognized by Charles Darwin.
In fact, he started out his book The Origin of Species with a chapter on variation in domestic animals. In this chapter, Darwin discussed in particular the pigeon. He wrote:
Altogether at least a score of pigeons might be chosen, which if shown to an ornithologist, and he were told that they were wild birds, would certainly, I think, be ranked by him as well-defined species.
Moreover, I do not believe that any ornithologist would place the English carrier, the short-faced tumbler, the runt, the barb, pouter, and fantail in the same genus; more especially as in each of these breeds several truly-inherited sub-breeds, or species as he might have called them, could be shown him.
I am fully convinced that the common opinion of naturalists is correct, namely, that all have descended from the rock-pigeon (Columba livia), including under this term several geographical races or sub-species, which differ from each other in the most trifling respects.
— Charles Darwin, The Origin of Species
In fact, he started out his book The Origin of Species with a chapter on variation in domestic animals. In this chapter, Darwin discussed in particular the pigeon. He wrote:
Altogether at least a score of pigeons might be chosen, which if shown to an ornithologist, and he were told that they were wild birds, would certainly, I think, be ranked by him as well-defined species.
Moreover, I do not believe that any ornithologist would place the English carrier, the short-faced tumbler, the runt, the barb, pouter, and fantail in the same genus; more especially as in each of these breeds several truly-inherited sub-breeds, or species as he might have called them, could be shown him.
I am fully convinced that the common opinion of naturalists is correct, namely, that all have descended from the rock-pigeon (Columba livia), including under this term several geographical races or sub-species, which differ from each other in the most trifling respects.
— Charles Darwin, The Origin of Species
Early experimental evolution - One of the first to carry out a controlled evolution experiment was William Dallinger. In the late 19th century, he cultivated small unicellular organisms in a custom-built incubator over a time period of seven years (1880–1886).
Dallinger slowly increased the temperature of the incubator from an initial 60 °F up to 158 °F. The early cultures had shown clear signs of distress at a temperature of 73 °F, and were certainly not capable of surviving at 158 °F.
The organisms Dallinger had in his incubator at the end of the experiment, on the other hand, were perfectly fine at 158 °F. However, these organisms would no longer grow at the initial 60 °F.
Dallinger concluded that he had found evidence for Darwinian adaptation in his incubator, and that the organisms had adapted to live in a high-temperature environment. Unfortunately, Dallinger's incubator was accidentally destroyed in 1886, and Dallinger could not continue this line of research.
Dallinger slowly increased the temperature of the incubator from an initial 60 °F up to 158 °F. The early cultures had shown clear signs of distress at a temperature of 73 °F, and were certainly not capable of surviving at 158 °F.
The organisms Dallinger had in his incubator at the end of the experiment, on the other hand, were perfectly fine at 158 °F. However, these organisms would no longer grow at the initial 60 °F.
Dallinger concluded that he had found evidence for Darwinian adaptation in his incubator, and that the organisms had adapted to live in a high-temperature environment. Unfortunately, Dallinger's incubator was accidentally destroyed in 1886, and Dallinger could not continue this line of research.
Modern experimental evolution - From the 1880s to 1980, experimental evolution was intermittently practiced by a variety of evolutionary biologists, including the highly influential Theodosius Dobzhansky.
Like other experimental research in evolutionary biology during this period, much of this work lacked extensive replication and was carried out only for relatively short periods of evolutionary time.
But by 1980, a variety of evolutionary biologists realized that the key to successful experimentation lay in extensive parallel replication of evolving lineages as well as a larger number of generations of selection.
One of the first of a new wave of experiments using this strategy was the laboratory "evolutionary radiation" of Drosophila melanogaster populations that Michael R. Rose started in February, 1980.
Like other experimental research in evolutionary biology during this period, much of this work lacked extensive replication and was carried out only for relatively short periods of evolutionary time.
But by 1980, a variety of evolutionary biologists realized that the key to successful experimentation lay in extensive parallel replication of evolving lineages as well as a larger number of generations of selection.
One of the first of a new wave of experiments using this strategy was the laboratory "evolutionary radiation" of Drosophila melanogaster populations that Michael R. Rose started in February, 1980.
This system started with ten populations, five cultured at later ages, and five cultured at early ages. Since then more than 200 different populations have been created in this laboratory radiation, with selection targeting multiple characters.
Some of these highly differentiated populations have also been selected "backward" or "in reverse," by returning experimental populations to their ancestral culture regime. Hundreds of people have worked with these populations over the better part of three decades. Much of this work is summarized in the papers collected in the book Methuselah Flies.
Lenski's long-term evolution experiment with Escherichia coli - On February 15, 1988, Richard Lenski started a long-term evolution experiment with the bacterium E. coli.
The experiment continues to this day, and is by now probably the largest controlled evolution experiment ever undertaken. Since the inception of the experiment, the bacteria have grown for more than 50,000 generations. Lenski and colleagues regularly publish updates on the status of the experiments.
Some of these highly differentiated populations have also been selected "backward" or "in reverse," by returning experimental populations to their ancestral culture regime. Hundreds of people have worked with these populations over the better part of three decades. Much of this work is summarized in the papers collected in the book Methuselah Flies.
Lenski's long-term evolution experiment with Escherichia coli - On February 15, 1988, Richard Lenski started a long-term evolution experiment with the bacterium E. coli.
The experiment continues to this day, and is by now probably the largest controlled evolution experiment ever undertaken. Since the inception of the experiment, the bacteria have grown for more than 50,000 generations. Lenski and colleagues regularly publish updates on the status of the experiments.
Garland's long-term experiment with laboratory house mice - In 1993, Theodore Garland, Jr. and colleagues started a long-term experiment that involves selective breeding for high voluntary activity levels on running wheels - movie.
This experiment also continues to this day (> 50 generations). Mice from the four replicate "High Runner" lines evolved to run 3 times as many running-wheel revolutions per day as compared with the four unselected control mice groups, mainly by running faster than the control mice rather than running for more minutes/day.
This experiment also continues to this day (> 50 generations). Mice from the four replicate "High Runner" lines evolved to run 3 times as many running-wheel revolutions per day as compared with the four unselected control mice groups, mainly by running faster than the control mice rather than running for more minutes/day.
The HR mice exhibit an elevated maximal aerobic capacity when tested on a motorized treadmill and a variety of other traits that appear to be adaptations that facilitate high levels of sustained endurance running (e.g., larger hearts, more symmetrical hindlimb bones).
They also exhibit alterations in motivation and the reward system of the brain. Pharmacological studies point to alterations in dopamine function and the endocannabinoid system. The High Runner lines have been proposed as a model to study human attention-deficit hyperactivity disorder (ADHD), and administration of Ritalin reduces their wheel running approximately to the levels of Control mice.
Source - Experimental evolution
They also exhibit alterations in motivation and the reward system of the brain. Pharmacological studies point to alterations in dopamine function and the endocannabinoid system. The High Runner lines have been proposed as a model to study human attention-deficit hyperactivity disorder (ADHD), and administration of Ritalin reduces their wheel running approximately to the levels of Control mice.
Source - Experimental evolution
Artificial selection
Artificial selection (or selective breeding) describes intentional breeding for certain traits, or combination of traits.
The term was utilized by Charles Darwin in contrast to natural selection, in which the differential reproduction of organisms with certain traits is attributed to improved survival or reproductive ability (“Darwinian fitness”).
As opposed to artificial selection, in which humans favor specific traits, in natural selection the environment acts as a sieve through which only certain variations can pass.
The term was utilized by Charles Darwin in contrast to natural selection, in which the differential reproduction of organisms with certain traits is attributed to improved survival or reproductive ability (“Darwinian fitness”).
As opposed to artificial selection, in which humans favor specific traits, in natural selection the environment acts as a sieve through which only certain variations can pass.
The deliberate exploitation of artificial selection has become very common in experimental biology, as well as the discovery and invention of new drugs. Artificial selection can also be unintentional; it is thought that domestication of crops by early humans was largely unintentional.
Historical development - Artificial selection was practiced by the Romans. Treatises as much as 2,000 years old give advice on selecting animals for different purposes, and these ancient works cite still older authorities, such as Mago the Carthaginian.
The notion of artificial selection was later expressed by the Persian Muslim polymath Abu Rayhan Biruni in the 11th century. He noted the idea in his book titled India, and gave various examples.
The agriculturist selects his corn, letting grow as much as he requires, and tearing out the remainder.
The forester leaves those branches which he perceives to be excellent, whilst he cuts away all others.
The bees kill those of their kind who only eat, but do not work in their beehive.
The notion of artificial selection was later expressed by the Persian Muslim polymath Abu Rayhan Biruni in the 11th century. He noted the idea in his book titled India, and gave various examples.
The agriculturist selects his corn, letting grow as much as he requires, and tearing out the remainder.
The forester leaves those branches which he perceives to be excellent, whilst he cuts away all others.
The bees kill those of their kind who only eat, but do not work in their beehive.
Charles Darwin coined the term as an illustration of his proposed wider process of natural selection. Darwin noted that many domesticated animals and plants had special properties that were developed by intentional animal and plant breeding from individuals that showed desirable characteristics, and discouraging the breeding of individuals with less desirable characteristics.
Darwin used the term twice in the 1859 first edition of his work On the Origin of Species, in Chapter IV: Natural Selection, and in Chapter VI: Difficulties on Theory –
Slow though the process of selection may be, if feeble man can do much by his powers of artificial selection, I can see no limit to the amount of change, to the beauty and infinite complexity of the co-adaptations between all organic beings, one with another and with their physical conditions of life, which may be effected in the long course of time by nature's power of selection.
We are profoundly ignorant of the causes producing slight and unimportant variations; and we are immediately made conscious of this by reflecting on the differences in the breeds of our domesticated animals in different countries, more especially in the less civilized countries where there has been but little artificial selection.
Darwin used the term twice in the 1859 first edition of his work On the Origin of Species, in Chapter IV: Natural Selection, and in Chapter VI: Difficulties on Theory –
Slow though the process of selection may be, if feeble man can do much by his powers of artificial selection, I can see no limit to the amount of change, to the beauty and infinite complexity of the co-adaptations between all organic beings, one with another and with their physical conditions of life, which may be effected in the long course of time by nature's power of selection.
We are profoundly ignorant of the causes producing slight and unimportant variations; and we are immediately made conscious of this by reflecting on the differences in the breeds of our domesticated animals in different countries, more especially in the less civilized countries where there has been but little artificial selection.
Contrast to natural selection - There is no real difference in the genetic processes underlying artificial and natural selection, and the concept of artificial selection was used by Charles Darwin as an illustration of the wider process of natural selection.
The selection process is termed "artificial" when human preferences or influences have a significant effect on the evolution of a particular population or species.
Indeed, many evolutionary biologists view domestication as a type of natural selection and adaptive change that occurs as organisms are brought under the control of human beings.
The selection process is termed "artificial" when human preferences or influences have a significant effect on the evolution of a particular population or species.
Indeed, many evolutionary biologists view domestication as a type of natural selection and adaptive change that occurs as organisms are brought under the control of human beings.
The deliberate exploitation of artificial selection has become very common in experimental biology, as well as the discovery and invention of new drugs. Artificial selection can also be unintentional; it is thought that domestication of crops by early humans was largely unintentional.
Laboratory usage - The deliberate exploitation of selective power has become common in experimental biology, particularly in microbiology and genetics.
In a ubiquitous laboratory technique in genetic engineering, genes are introduced into cells in cell culture, usually bacteria, on a small circular DNA molecule called a plasmid in a process called transfection.
The gene of interest is accompanied on the plasmid by a reporter gene, or "selectable marker", which encodes a specific trait such as antibiotic resistance or ability to grow in high salt concentrations.
The cells can then be cultured in an environment that would kill normal cells, but is hospitable to those that have taken up and expressed the genes on the plasmid. In this way expression of the reporter gene serves as a signal that the gene of interest is also being expressed in the cells.
In a ubiquitous laboratory technique in genetic engineering, genes are introduced into cells in cell culture, usually bacteria, on a small circular DNA molecule called a plasmid in a process called transfection.
The gene of interest is accompanied on the plasmid by a reporter gene, or "selectable marker", which encodes a specific trait such as antibiotic resistance or ability to grow in high salt concentrations.
The cells can then be cultured in an environment that would kill normal cells, but is hospitable to those that have taken up and expressed the genes on the plasmid. In this way expression of the reporter gene serves as a signal that the gene of interest is also being expressed in the cells.
Another technique used in drug development uses an iterative selective process called in vitro selection to evolve aptamers, or nucleic acid fragments capable of binding specific organic compounds with high binding affinity.
Studies in evolutionary physiology, behavioral genetics, and other areas of organismal biology have also made use of deliberate artificial selection, though longer generation times and greater difficulty in breeding can make such projects challenging in vertebrates. Source - Artificial selection
Studies in evolutionary physiology, behavioral genetics, and other areas of organismal biology have also made use of deliberate artificial selection, though longer generation times and greater difficulty in breeding can make such projects challenging in vertebrates. Source - Artificial selection
Selective breeding
A Belgian Blue cow. The defect in the breed's myostatin gene is maintained through linebreeding and is responsible for its accelerated lean muscle growth
Selective breeding is the process of breeding plants and animals for particular traits. Typically, strains that are selectively bred are domesticated, and the breeding is sometimes done by a professional breeder.
Bred animals are known as breeds, while bred plants are known as varieties, cultigens, or cultivars.
The cross of animals results in what is called a crossbreed, and crossbred plants are called hybrids. The term selective breeding is synonymous with artificial selection.
Selective breeding is the process of breeding plants and animals for particular traits. Typically, strains that are selectively bred are domesticated, and the breeding is sometimes done by a professional breeder.
Bred animals are known as breeds, while bred plants are known as varieties, cultigens, or cultivars.
The cross of animals results in what is called a crossbreed, and crossbred plants are called hybrids. The term selective breeding is synonymous with artificial selection.
In animal breeding techniques such as inbreeding, linebreeding, and outcrossing are utilized. In plant breeding, similar methods are used. Charles Darwin discussed how selective breeding had been successful in producing change over time in his book, Origin of Species. The first chapter of the book discusses selective breeding and domestication of such animals as pigeons, dogs and cattle. Selective breeding was used by Darwin as a springboard to introduce the theory of natural selection, and to support it.
Animal breeding - Animals with homogeneous appearance, behavior, and other characteristics are known as particular breeds, and they are bred through culling particular traits and selecting for others.
Purebred animals have a single, recognizable breed, and purebreds with recorded lineage are called pedigreed.
Crossbreeds are a mix of two purebreds, whereas mixed breeds are a mix of several breeds, often unknown. Animal breeding begins with breeding stock, a group of animals used for the purpose of planned breeding.
When individuals are looking to breed animals, they look for certain valuable traits in purebred stock for a certain purpose, or may intend to use some type of crossbreeding to produce a new type of stock with different, and, it is presumed, superior abilities in a given area of endeavor.
Purebred animals have a single, recognizable breed, and purebreds with recorded lineage are called pedigreed.
Crossbreeds are a mix of two purebreds, whereas mixed breeds are a mix of several breeds, often unknown. Animal breeding begins with breeding stock, a group of animals used for the purpose of planned breeding.
When individuals are looking to breed animals, they look for certain valuable traits in purebred stock for a certain purpose, or may intend to use some type of crossbreeding to produce a new type of stock with different, and, it is presumed, superior abilities in a given area of endeavor.
For example, to breed chickens, a typical breeder intends to receive eggs, meat, and new, young birds for further reproduction.
Thus, the breeder has to study different breeds and types of chickens and analyze what can be expected from a certain set of characteristics before he or she starts breeding them.
Therefore, when purchasing initial breeding stock, the breeder seeks a group of birds that will most closely fit the purpose intended.
Thus, the breeder has to study different breeds and types of chickens and analyze what can be expected from a certain set of characteristics before he or she starts breeding them.
Therefore, when purchasing initial breeding stock, the breeder seeks a group of birds that will most closely fit the purpose intended.
Purebred breeding aims to establish and maintain stable traits, that animals will pass to the next generation.
By "breeding the best to the best," employing a certain degree of inbreeding, considerable culling, and selection for "superior" qualities, one could develop a bloodline superior in certain respects to the original base stock.
Such animals can be recorded with a breed registry, the organization that maintains pedigrees and/or stud books.
However, single-trait breeding, breeding for only one trait over all others, can be problematic. In one case mentioned by animal behaviorist Temple Grandin, roosters bred for fast growth or heavy muscles did not know how to perform typical rooster courtship dances, which alienated the roosters from hens and led the roosters to kill the hens after reproducing with them.
The observable phenomenon of hybrid vigor stands in contrast to the notion of breed purity. However, on the other hand, indiscriminate breeding of crossbred or hybrid animals may also result in degradation of quality.
Source - Selective breeding
By "breeding the best to the best," employing a certain degree of inbreeding, considerable culling, and selection for "superior" qualities, one could develop a bloodline superior in certain respects to the original base stock.
Such animals can be recorded with a breed registry, the organization that maintains pedigrees and/or stud books.
However, single-trait breeding, breeding for only one trait over all others, can be problematic. In one case mentioned by animal behaviorist Temple Grandin, roosters bred for fast growth or heavy muscles did not know how to perform typical rooster courtship dances, which alienated the roosters from hens and led the roosters to kill the hens after reproducing with them.
The observable phenomenon of hybrid vigor stands in contrast to the notion of breed purity. However, on the other hand, indiscriminate breeding of crossbred or hybrid animals may also result in degradation of quality.
Source - Selective breeding