Domestication is a multi-generational mutualistic relationship in which an animal species, such as humans or , takes over control and care of another species, such as sheep or fungi, to obtain from them a steady supply of resources, such as meat, milk, or labor. The process is gradual and geographically diffuse, based on trial and error. Domestication affected genes for behavior in animals, making them less aggressive. In plants, domestication affected genes for morphology, such as increasing seed size and stopping the shattering of cereal seedheads. Such changes both make domesticated organisms easier to handle and reduce their ability to survive in the wild.
The first animal to be domesticated by humans was the dog, as a Commensalism, at least 15,000 years ago. Other animals, including , sheep, and , were domesticated around 11,000 years ago. Among birds, the chicken was first domesticated in East Asia, seemingly for cockfighting, some 7,000 years ago. The horse came under domestication around 5,500 years ago in central Asia as a working animal. Among , the silkworm and the western honey bee were domesticated over 5,000 years ago for silk and honey, respectively.
The domestication of plants began around 13,000–11,000 years ago with such as wheat and barley in the Middle East, alongside crops such as lentil, pea, chickpea, and flax. Beginning around 10,000 years ago, Indigenous peoples in the Americas began to cultivate , squash, maize, , cotton, and cassava. Rice was first domesticated in China some 9,000 years ago. In Africa, crops such as sorghum were domesticated. Agriculture developed in some 13 centres around the world, domesticating different crops and animals.
Three groups of insects, namely , , and fungus-growing termites have independently domesticated species of fungi, on which they feed. In the case of the termites, the relationship is a fully obligate symbiosis on both sides.
Definitions
Domestication (not to be confused with the
tame animal of an individual animal
), is from the
Latin language domesticus, 'belonging to the house'.
The term remained loosely defined until the 21st century, when the American archaeologist Melinda A. Zeder defined it as a long-term relationship in which humans take over control and care of another organism to gain a predictable supply of a resource, resulting in mutual benefits. She noted further that it is not synonymous with agriculture since agriculture depends on domesticated organisms but does not automatically result from domestication.
Michael D. Purugganan notes that domestication has been hard to define, despite the "instinctual consensus" that it means "the plants and animals found under the care of humans that provide us with benefits and which have evolved under our control."
Domestication syndrome is the suite of phenotype traits that arose during the initial domestication process and which distinguish crops from their .
Cause and timing
The domestication of animals and plants by humans was triggered by the climatic and environmental changes that occurred after the peak of the Last Glacial Maximum and which continue to this present day. These changes made obtaining food by
Hunter-gatherer difficult.
The first animal to be domesticated was the dog at least 15,000 years ago.
The
Younger Dryas 12,900 years ago was a period of intense cold and aridity that put pressure on humans to intensify their foraging strategies but did not favour agriculture. By the beginning of the
Holocene 11,700 years ago, a warmer climate and increasing human populations led to small-scale animal and plant domestication and an increased supply of food.
| + Timeline of some major domestication events |
|
> 23,000 |
> 15,000 |
13,000–11,000 |
| 13,000–11,000 |
| Cannabis | East Asia | Textiles | 12,000 |
11,000–10,000 |
9,000 |
7,000 |
5,500 |
> 5,000 |
The appearance of the domestic dog in the archaeological record, at least 15,000 years ago, was followed by domestication of livestock and of crops such as wheat and barley, the invention of agriculture, and the transition of humans from foraging to farming in different places and times across the planet.
In the Fertile Crescent 11,000–10,000 years ago, zooarchaeology indicates that goats, pigs, sheep, and taurine cattle were the first livestock to be domesticated. Two thousand years later, humped zebu cattle were domesticated in what is today Baluchistan in Pakistan. In East Asia 8,000 years ago, pigs were domesticated from wild boar genetically different from those found in the Fertile Crescent.
File:Centres of origin and spread of agriculture labelled.svg|Vavilov center and spread of agriculture in the Neolithic Revolution as understood in 2003
Animals
Desirable traits
The domestication of vertebrate animals is the relationship between non-human vertebrates and humans who have an influence on their care and reproduction.
In his 1868 book
The Variation of Animals and Plants Under Domestication,
Charles Darwin recognized the small number of traits that made domestic species different from their wild ancestors. He was also the first to recognize the difference between conscious selective breeding in which humans directly select for desirable traits and unconscious selection, in which traits evolve as a by-product of natural selection or from selection on other traits.
There is a difference between domestic and wild populations; some of these differences constitute the domestication syndrome, traits presumed essential in the early stages of domestication, while others represent later improvement traits.
Certain animal species, and certain individuals within those species, make better candidates for domestication because of their behavioral characteristics:
-
The size and organization of their social structure
-
The availability and the degree of selectivity in their choice of mates
-
The ease and speed with which the parents bond with their young, and the maturity and mobility of the young at birth
-
The degree of flexibility in diet and habitat tolerance
-
Responses to humans and new environments, including reduced flight response and reactivity to external stimuli.
Mammals
The beginnings of mammal domestication involved a protracted
process with multiple stages along different pathways. There are three proposed major pathways that most mammal domesticates followed into domestication:
-
Commensalism, adapted to a human niche (e.g., dogs, cats, possibly pigs)
-
prey animals sought for food (e.g., sheep, goats, cattle, water buffalo, Domestic yak, pig, reindeer, llama and alpaca)
-
animals targeted pack animal and Equestrianism (e.g., horse, donkey, camel).
Humans did not intend to domesticate mammals from either the commensal or prey pathways, or at least they did not envision a domesticated animal would result from it. In both of those cases, humans became entangled with these species as the relationship between them intensified, and humans' role in their survival and reproduction gradually led to formalized animal husbandry.
Unlike other domestic species selected primarily for production-related traits, dogs were initially selected for their behaviors.
The archaeological and genetic data suggest that long-term bidirectional gene flow between wild and domestic stocks – such as in , , New and Old World camelids, goats, sheep, and pigs – was common.
The 2023 parasite-mediated domestication hypothesis suggests that endoparasites such as helminths and protozoa could have mediated the domestication of mammals. Domestication involves taming, which has an endocrine component; and parasites can modify endocrine activity and . Genes for resistance to parasites might be linked to those for the domestication syndrome; it is predicted that domestic animals are less resistant to parasites than their wild relatives.
Birds
Domesticated birds principally mean
poultry, raised for meat and eggs:
some
Galliformes (
chicken, turkey,
guineafowl) and
Anseriformes (waterfowl:
,
goose, and
). Also widely domesticated are
cagebirds such as
songbirds and
parrots; these are kept both for pleasure and for use in research.
The
domestic pigeon has been used both for food and as a means of communication between far-flung places through the exploitation of the pigeon's homing instinct; research suggests it was domesticated as early as 10,000 years ago.
Chicken fossils in China have been dated to 7,400 years ago. The chicken's wild ancestor is
Gallus gallus, the red junglefowl of Southeast Asia. The species appears to have been kept initially for
cockfighting rather than for food.
Invertebrates
Two
, the
silkworm and the western honey bee, have been domesticated for over 5,000 years, often for commercial use. The silkworm is raised for the silk threads wound around its
cocoon; the western honey bee, for
honey, and, from the 20th century, for
pollination of crops.
Several other invertebrates have been domesticated, both terrestrial and aquatic, including some such as Drosophila melanogaster fruit flies and the freshwater cnidarian Hydra for research into genetics and physiology. Few have a long history of domestication. Most are used for food or other products such as shellac and cochineal. The phylum involved are Cnidaria, Platyhelminthes (for biological pest control), Annelida, Mollusca, Arthropoda (marine as well as insects and spiders), and Echinodermata. While many marine mollusks are used for food, only a few have been domesticated, including Loligo, cuttlefish and octopus, all used in research on animal behaviour and neurology. Terrestrial snails in the genera Helix are raised for food. Several parasitic or parasitoidal insects, including the fly Eucelatoria, the beetle Chrysolina, and the wasp Aphytis are raised for biological control. Conscious or unconscious artificial selection has many effects on species under domestication; variability can readily be lost by inbreeding, selection against undesired traits, or genetic drift, while in Drosophila, variability in eclosion time (when adults emerge) has increased.
File:Cueva arana.svg|A Honey hunting in a cave painting at Cuevas de la Araña, Spain, c. 8,000–6,000 BC
File:Sericuturist.jpg|Sericulture preparing for spinning of the silk
File:02-Indian-Insect-Life - Harold Maxwell-Lefroy - Kerria-Lacca.jpg|The lac bug Kerria lacca has been kept for shellac resin.
File:Snails for Sale - Djermaa el-Fna (Central Square) - Medina (Old City) - Marrakesh - Morocco.jpg|Snails being sold as food
Plants
Humans
Foraging for wild cereals, seeds, and nuts thousands of years before they were domesticated; wild wheat and barley, for example, were gathered in the
Levant at least 23,000 years ago.
[Weiss, E., Kislev, M.E., Simchoni, O. & Nadel, D. Small-grained wild grasses as staple food at the 23000-year-old site of Ohalo II Economic Botany 58:s125-s134.] societies in West Asia first began to cultivate and then domesticate some of these plants around 13,000 to 11,000 years ago.
The
founder crops of the West Asian Neolithic included cereals (
emmer,
einkorn wheat,
barley), pulses (
lentil,
pea,
chickpea,
Vicia ervilia), and
flax. Other plants were independently domesticated in 13 centers of origin (subdivided into 24 areas) of the Americas, Africa, and Asia (the Middle East, South Asia, the Far East, and New Guinea and Wallacea); in some thirteen of these regions people began to cultivate grasses and grains.
Rice was first cultivated in East Asia.
["New Archaeobotanic Data for the Study of the Origins of Agriculture in China", Zhijun Zhao, Current Anthropology Vol. 52, No. S4, (October 2011), pp. S295-S306] Sorghum was widely cultivated in sub-Saharan Africa,
while peanuts,
squash,
cotton,
,
,
and
cassava were domesticated in the Americas.
Continued domestication was gradual and geographically diffuse – happening in many small steps and spread over a wide area – on the evidence of both archaeology and genetics.
Whereas domestication of animals impacted most on the genes that controlled behavior, that of plants impacted most on the genes that controlled morphology (seed size, plant architecture, dispersal mechanisms) and physiology (timing of germination or ripening),
File:Maler der Grabkammer des Menna 012.jpg|Farmers with wheat and cattle – art 3,400 years ago
File:Harold f Weston - Iran11.jpg|Wild wheat ears shatter when ripe, but domesticated wheat has to be threshing and Winnowing (as shown) to release and separate the grain. Photograph by Harold Weston, Iran, 1920s
Differences from wild plants
Domesticated plants differ from their wild relatives in many ways, including
-
lack of shattering such as of cereal ears (ripe heads),
-
less efficient breeding system (e.g. without normal pollinating organs, making human intervention a requirement), larger seeds with lower success in the wild,
-
better palatability (e.g. higher sugar content, reduced bitterness), better smell, and lower toxicity
-
edible part larger, e.g. cereal grains
-
edible part more easily separated from non-edible part
-
increased number of fruits or grains
-
altered color, taste, and texture
-
daylength independence
-
determinate growth
-
reduced or no vernalization
-
less seed dormancy.
Plant defenses against herbivory, such as thorns, spines, and prickles, poison, protective coverings, and sturdiness may have been reduced in domesticated plants. This would make them more likely to be eaten by herbivores unless protected by humans, but there is only weak support for most of this.
Changes to plant genome
During domestication, crop species undergo intense artificial selection that alters their genomes, establishing core traits that define them as domesticated, such as increased grain size.
Comparison of the
coding DNA of
chromosome 8 in rice between fragrant and non-fragrant varieties showed that aromatic and fragrant rice, including
basmati and
Jasmine rice, is derived from an ancestral rice domesticate that suffered a deletion in
exon 7 which altered the coding for betaine aldehyde dehydrogenase (BADH2).
Comparison of the potato genome with that of other plants located genes for resistance to potato blight caused by
Phytophthora infestans.
In coconut, genomic analysis of 10 microsatellite loci (of noncoding DNA) found two episodes of domestication based on differences between individuals in the Indian Ocean and those in the Pacific Ocean.
In wheat, domestication involved repeated hybridization and polyploidy. These steps are large and essentially instantaneous changes to the genome and the epigenome, enabling a rapid evolutionary response to artificial selection. Polyploidy increases the number of chromosomes, bringing new combinations of genes and alleles, which in turn evolvability such as by chromosomal crossover.
Impact on plant microbiome
The
microbiome, the collection of
inhabiting the surface and internal tissue of plants, is affected by domestication. This includes changes in microbial species composition
and diversity.
Plant lineage, including
speciation, domestication, and
Plant breeding, have shaped plant
(
phylosymbiosis) in similar patterns as plant genes.
Fungi
Several species of
fungi have been domesticated for use directly as food, or in fermentation to produce foods and drugs. The cultivated mushroom
Agaricus bisporus is widely grown for food.
The yeast
Saccharomyces cerevisiae have been used for thousands of years to ferment
beer and
wine, and to leaven
bread.
Mould fungi including
Penicillium are used to mature
and other dairy products, as well as to make drugs such as
antibiotics.
Effects
On domestic animals and pathogens
Selection of animals for visible traits may have undesired consequences for the genetics of domestic animals.
A side effect of domestication has been
zoonotic diseases. For example, cattle have given humanity various
Poxviridae,
measles, and
tuberculosis; pigs and ducks have contributed
influenza; and horses have brought the
. Many
, too, have their origins in domestic animals. Alongside these, 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.
On society
Scholars have expressed widely differing viewpoints on domestication's effects on society. Anarcho-primitivism critiques domestication as destroying the supposed primitive state of harmony with nature in hunter-gatherer societies, and replacing it, possibly violently or by enslavement, with a social
hierarchy as property and power emerged.
The dialectal naturalist
Murray Bookchin has argued that domestication of animals, in turn, meant the domestication of humanity, both parties being unavoidably altered by their relationship with each other.
The sociologist
David Nibert asserts that the domestication of animals involved violence against animals and damage to the environment. This, in turn, he argues, corrupted human ethics and paved the way for "conquest, extermination, displacement, repression, coerced and enslaved servitude, gender subordination and sexual exploitation, and hunger."
On diversity
Domesticated ecosystems provide food, reduce predator and natural dangers, and promote commerce, but their creation has resulted in habitat alteration or loss, and multiple extinctions commencing in the Late Pleistocene.
Domestication reduces genetic diversity of the domesticated population, especially of alleles of genes targeted by selection.
Domestication by insects
At least three groups of insects, namely ambrosia beetles, leafcutter ants, and fungus-growing termites, have domesticated species of
Fungus.
Ambrosia beetles
Ambrosia beetles in the
weevil subfamilies
Scolytinae and
Platypodinae excavate tunnels in dead or stressed trees into which they introduce fungal gardens, their sole source of nutrition. After landing on a suitable tree, an ambrosia beetle excavates a tunnel in which it releases
Ambrosia fungi. The fungus penetrates the plant's
xylem tissue, extracts nutrients from it, and concentrates the nutrients on and near the surface of the beetle gallery. Ambrosia fungi are typically poor wood degraders and instead utilize less demanding nutrients.
Symbiotic fungi produce and detoxify ethanol, which is an attractant for ambrosia beetles and likely prevents the growth of antagonistic pathogens and selects for other beneficial symbionts.
Ambrosia beetles mainly colonise wood of recently dead trees.
Leafcutter ants
The leafcutter ants are any of some 47 species of leaf-chewing ants in the genera
Acromyrmex and
Atta. The ants carry the discs of leaves that they have cut back to their nest, where they feed the leaf material to the fungi that they tend. Some of these fungi are not fully domesticated: the fungi farmed by
Mycocepurus smithii constantly produce spores that are not useful to the ants, which eat fungal
instead. The process of domestication by
Atta ants, on the other hand, is complete; it took 30 million years.
Fungus-growing termites
Some 330 fungus-growing termite species of the subfamily
Macrotermitinae cultivate
Termitomyces fungi to eat; domestication occurred exactly once, 25–40 mya.
The fungi, described by
Roger Heim in 1942, grow on 'combs' formed from the termites' excreta, dominated by tough woody fragments.
The termites and the fungi are both obligate
symbiosis in the relationship.
File:Xylosandrus crassiusculus galleryR.jpg|Gallery of the ambrosia beetle Xylosandrus crassiusculus split open, with pupae and black fungus. The fungus decomposes materials in the wood, providing food for the beetles.
File:leaf cutter ants arp.jpg|Leafcutter ants Atta cephalotes carrying discs of leaf material back to their nest to feed to their domesticated fungus
Ancistrotermes latinotus.jpg|Inside the nest of the fungus-cultivating termite Ancistrotermes
File:Termitomyces heimii.jpg| Termitomyces heimii growing on 'comb' inside a termite mound
File:Termitomyces reticulatus 37340.jpg| Termitomyces fungi are mutually dependent on Macrotermitinae termites for their survival.
See also
-
Anthrozoology
-
De novo domestication
-
Domestication theory
-
Experimental evolution
-
Genetic erosion
-
Self-domestication
-
Timeline of agriculture and food technology
Sources
External links
