Selective breeding of plants and animals to serve humans
Dogs andsheep were among the first animals to be domesticated, at least 15,000 and 11,000 years ago respectively.[1]Rice was domesticated in China, some 9,000 years ago.[2]
Domestication is a multi-generationalmutualistic relationship in which an animal species, such as humans orleafcutter ants, takes over control and care of another species, such as sheep orfungi, to obtain from them a steady supply of resources, such asmeat,milk, or labor. The process is gradual and geographically diffuse, based ontrial and error. Domestication affectsgenes for behavior in animals, making them less aggressive. In plants, domestication affects genes formorphology, such as increasing seed size and stopping theshattering of cereal seedheads. Such changes both make domesticatedorganisms easier to handle and reduce their ability to survive in the wild.
Domestication (not to be confused with thetaming of an individual animal[3][4][5]), is from theLatindomesticus, 'belonging to the house'.[6] The term remained loosely defined until the 21st century, when the AmericanarchaeologistMelinda 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 inmutual benefits. She noted further that it is not synonymous withagriculture since agriculture depends on domesticated organisms but does not automatically result from domestication.[7]
Diagram of domestication as a process where one species actively manages another to obtain resources or services, as defined byMichael D. Purugganan[8]
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."[8] He comments that insects such astermites,ambrosia beetles, andleafcutter ants have domesticated some species offungi, and notes further that other groups such as weeds andcommensals have wrongly been called domesticated.[8] Starting from Zeder's definition, Purugganan proposes a "broad" definition: "acoevolutionary process that arises from amutualism, in which one species (the domesticator) constructs an environment where it actively manages both thesurvival and reproduction of another species (the domesticate) in order to provide the former with resources and/or services."[8] He comments that this addsniche construction to the activities of the domesticator.[8]
Domestication syndrome is the suite ofphenotypic traits that arose during the initial domestication process and which distinguish crops from theirwild ancestors.[9][10] It can also mean a set of differences now observed in domesticated mammals, not necessarily reflecting the initial domestication process. The changes include increased docility and tameness, coat coloration, reductions in tooth size, craniofacial morphology, ear and tail form (e.g., floppy ears), estrus cycles, levels ofadrenocorticotropic hormone andneurotransmitters, prolongations in juvenile behavior, and reductions in brain size and of particularbrain regions.[11]
A 2025 article published inPNAS proposed a formal definition of domestication, defined simply:
As evolution in response to ananthropogenic niche. It is the process in which a nonhuman population adapts to an environment created through human activity.[12]
Furthermore, the term “domestic” should refer solely to those populations that are obligatesynanthropes and have adapted to ananthropogenic environment to the extent that only sink populations (in which the death rate is higher than the birth rate) exist outside of that niche.
Thedomestication of animals and plants by humans was triggered by the climatic and environmental changes that occurred after the peak of theLast Glacial Maximum and which continue to this present day. These changes made obtaining food byhunting and gathering difficult.[13] The first animal to bedomesticated was the dog at least 15,000 years ago.[1] TheYounger Dryas 12,900 years ago was a period of intense cold andaridity that put pressure on humans to intensify their foraging strategies but did not favour agriculture. By the beginning of theHolocene 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.[14]
The appearance of thedomestic dog in the archaeological record, at least 15,000 years ago, was followed by domestication oflivestock andof crops such aswheat andbarley, theinvention of agriculture, and the transition of humans fromforaging to farming in different places and times across the planet.[1][20][21][22] For instance, small-scale trial cultivation ofcereals began some 23,000 years ago at the Ohalo II site in Israel.[23]
Domesticated animals tend to be smaller and less aggressive than their wild counterparts; many have otherdomestication syndrome traits like shorter muzzles.[28] Skulls ofgrey wolf (left),chihuahua dog (right)
The domestication ofvertebrate animals is the relationship between non-human vertebrates and humans who have an influence on their care and reproduction.[7] In his 1868 bookThe 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 consciousselective breeding in which humans directly select for desirable traits and unconscious selection, in which traits evolve as a by-product ofnatural selection or from selection on other traits.[29][30][31]
There is a difference between domestic and wild populations; some of these differences constitute thedomestication syndrome, traits presumed essential in the early stages of domestication, while others represent later improvement traits.[9][32][33] Domesticatedmammals in particular tend to be smaller and less aggressive than their wild counterparts; other common traits are floppy ears, a smaller brain, and a shorter muzzle.[28] Domestication traits are generally fixed within all domesticates, and were selected during the initial episode of domestication of that animal or plant, whereas improvement traits are present only in a proportion of domesticates, though they may be fixed in individual breeds orregional populations.[32][33][34]
Certain animal species, and certain individuals within those species, make better candidates for domestication because of their behavioral characteristics:[35][36][37][38]
The beginnings of mammal domestication involved a protractedcoevolutionary process with multiple stages along different pathways. There are three proposed major pathways that most mammal domesticates followed into domestication:[35][33][39]
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 formalizedanimal husbandry.[33] Although the directed pathway for draft and riding animals proceeded from capture totaming, the other two pathways are not as goal-oriented, and archaeological records suggest that they took place over much longer time frames.[40]
Unlike other domestic species selected primarily for production-related traits, dogs were initially selected for their behaviors.[41][42] The dog was domesticated long before other animals,[43][44] becoming established acrossEurasia before the end of theLate Pleistocene era, well beforeagriculture.[43]
The archaeological and genetic data suggest that long-term bidirectionalgene flow between wild and domestic stocks – such as indonkeys,horses, New andOld Worldcamelids, goats, sheep, and pigs – was common.[33][39] Human selection for domestic traits likely counteracted the homogenizing effect ofgene flow fromwild boars into pigs, and createddomestication islands in the genome. The same process may apply to other domesticated animals.[45][46]
The 2023parasite-mediated domestication hypothesis suggests thatendoparasites such ashelminths andprotozoa could have mediated the domestication of mammals. Domestication involves taming, which has anendocrine component; and parasites can modify endocrine activity andmicroRNAs. 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.[47][48][49]
The chicken's wild ancestor isGallus gallus, thered junglefowl ofSoutheast Asia.[53] The date and place of chicken domestication has been debated by scientists: fossils in China and Pakistan have been suggested as early chickens at dates as old as 11,000 years ago. A 2020 study of chicken genomes confirmed that domestication occurred in Southeast Asia. Re-examination and dating of bones from many sites identified the earliest probable chicken bones as from centralThailand some 3250 years ago.[19]
Twoinsects, thesilkworm and thewestern honey bee, have been domesticated for over 5,000 years, often for commercial use. The silkworm is raised for the silk threads wound around itspupal cocoon; the western honey bee, forhoney, and, from the 20th century, forpollination of crops.[18][54]
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.[68] It was a process of intermittent trial and error and often resulted in diverging traits and characteristics.[69]
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 ofgermination orripening),[35][21] as in thedomestication of wheat. Wild wheatshatters and falls to the ground to reseed itself when ripe, but domesticated wheat stays on the stem for easier harvesting. This change was possible because of a random mutation in the wild populations at the beginning of wheat'scultivation. Wheat with this mutation was harvested more frequently and became the seed for the next crop. Therefore, without realizing it, early farmersselected for this mutation. The result is domesticated wheat, which relies on farmers for its reproduction and dissemination.[15]
Farmers with wheat and cattle –Ancient Egyptian art 3,400 years ago
Wildwheat ears shatter when ripe, but domesticated wheat has to bethreshed andwinnowed (as shown) to release and separate the grain. Photograph byHarold Weston, Iran, 1920s
less efficientbreeding system (e.g. without normalpollinating organs, making human intervention a requirement), larger seeds with lower success in the wild,[15] or even sterility (e.g.seedless fruits) and therefore only vegetative reproduction[72][73]
Plant defenses against herbivory, such asthorns, spines, and prickles, poison, protective coverings, and sturdiness may have been reduced in domesticated plants. This would make them more likely to be eaten byherbivores unless protected by humans, but there is only weak support for most of this.[74] Farmers did select for reduced bitterness and lower toxicity and for food quality, which likely increased crop palatability to herbivores as to humans.[74] However, a survey of 29 plant domestications found that crops were as well-defended against two major insect pests (beet armyworm andgreen peach aphid) both chemically (e.g. with bitter substances) and morphologically (e.g. with toughness) as their wild ancestors.[77]
Domesticatedwheat evolved by repeatedhybridization andpolyploidy from multiple wild ancestors, increasing the size and evolvability of the genome.[78]
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.[15][79] Comparison of thecoding DNA ofchromosome 8 in rice between fragrant and non-fragrant varieties showed that aromatic and fragrant rice, includingbasmati andjasmine, is derived from an ancestral rice domesticate that suffered a deletion inexon 7 which altered the coding for betaine aldehyde dehydrogenase (BADH2).[80] Comparison of the potato genome with that of other plants located genes for resistance to potato blight caused byPhytophthora infestans.[81]
In wheat, domestication involved repeatedhybridization andpolyploidy. These steps are large and essentially instantaneous changes to the genome and theepigenome, enabling a rapid evolutionary response to artificial selection. Polyploidy increases the number of chromosomes, bringing new combinations of genes and alleles, which in turnenable further changes such as bychromosomal crossover.[78]
Several species offungi have been domesticated for use directly as food, or in fermentation to produce foods and drugs. The cultivated mushroomAgaricus bisporus is widely grown for food.[91] The yeastSaccharomyces cerevisiae have been used for thousands of years to fermentbeer andwine, and to leavenbread.[92] Mould fungi includingPenicillium are used to maturecheeses and other dairy products, as well as to make drugs such asantibiotics.[93]
Selection of animals for visible traits may have undesired consequences for the genetics of domestic animals.[94] A side effect of domestication has beenzoonotic diseases. For example, cattle have given humanity variousviral poxes,measles, andtuberculosis; pigs and ducks have contributedinfluenza; and horses have brought therhinoviruses. Manyparasites, too, have their origins in domestic animals.[95] Alongside these, the advent of domestication resulted in denser human populations, which provided ripe conditions forpathogens to reproduce, mutate, spread, and eventually find a new host in humans.[96]
Scholars have expressed widely differing viewpoints on domestication's effects on society.Anarcho-primitivism critiques domestication as destroying the supposed primitive state ofharmony with nature inhunter-gatherer societies, and replacing it, possibly violently or byenslavement, with a socialhierarchy as property and power emerged.[97] Thedialectal naturalistMurray 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.[98] The sociologistDavid 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."[99]
Industrialized agriculture on land with a simplified ecosystem
Domesticated ecosystems provide food, reduce predator and natural dangers, and promote commerce, but their creation has resulted in habitat alteration or loss, and multipleextinctions commencing in theLate Pleistocene.[100]
Domestication reducesgenetic diversity of the domesticated population, especially ofalleles of genes targeted by selection.[101] One reason is apopulation bottleneck created by artificially selecting the most desirable individuals to breed from. Most of the domesticated strain is then born from just a few ancestors, creating a situation similar to thefounder effect.[102] Domesticated populations such as of dogs, rice, sunflowers, maize, and horses have an increasedmutation load, as expected in apopulation bottleneck where genetic drift is enhanced by the small population size. Mutations can also be fixed in a population by aselective sweep.[103][104]Mutational load can be increased by reduced selective pressure against moderately harmful traits when reproductive fitness is controlled by human management.[28] However, there is evidence against a bottleneck in crops, such as barley, maize, and sorghum, where genetic diversity slowly declined rather than showing a rapid initial fall at the point of domestication.[103][102] Further, the genetic diversity of these crops was regularly replenished from the natural population.[103] Similar evidence exists for horses, pigs, cows, and goats.[28]
Ambrosia beetles in theweevil subfamiliesScolytinae andPlatypodinae 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 releasesits fungal symbiont. The fungus penetrates the plant'sxylem 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.[106] 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.[107] Ambrosia beetles mainly colonise wood of recently dead trees.[108]
The leafcutter ants are any of some 47 species of leaf-chewing ants in the generaAcromyrmex andAtta. 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 byMycocepurus smithii constantly produce spores that are not useful to the ants, which eat fungalhyphae instead. The process of domestication byAtta ants, on the other hand, is complete; it took 30 million years.[109]
Some 330 fungus-growing termite species of the subfamilyMacrotermitinae cultivateTermitomyces fungi to eat; domestication occurred exactly once, 25–40mya.[8][105] The fungi, described byRoger Heim in 1942, grow on 'combs' formed from the termites' excreta, dominated by tough woody fragments.[110] The termites and the fungi are both obligatesymbionts in the relationship.[111]
Domestication by insects
Gallery of the ambrosia beetleXylosandrus crassiusculus split open, with pupae and black fungus. The fungus decomposes materials in the wood, providing food for the beetles.
Leafcutter antsAtta cephalotes carrying discs of leaf material back to their nest to feed to their domesticated fungus
Inside the nest of the fungus-cultivating termiteAncistrotermes
^Diamond, Jared (2012). "Chapter 1". In Gepts, P. (ed.).Biodiversity in Agriculture: Domestication, Evolution, and Sustainability.Cambridge University Press. p. 13.
^Fuller, Dorian Q.; Willcox, George; Allaby, Robin G. (2011). "Cultivation and domestication had multiple origins: Arguments against the core area hypothesis for the origins of agriculture in the Near East".World Archaeology.43 (4):628–652.doi:10.1080/00438243.2011.624747.S2CID56437102.
^abZeder, Melinda A. (2006). "Archaeological approaches to documenting animal domestication". In Zeder, M. A.; Bradley, D. G.; Emshwiller, E.; Smith, B. D. (eds.).Documenting Domestication: New Genetic and Archaeological Paradigms. Berkeley:University of California Press. pp. 209–227.
^Hale, E. B. (1969). "Domestication and the evolution of behavior". In Hafez, E. S. E. (ed.).The Behavior of Domestic Animals (2nd ed.). London: Bailliere, Tindall, and Cassell. pp. 22–42.
^Serpell, J.; Duffy, D. (2014). "Dog Breeds and Their Behavior". In Horowitz, Alexandra (ed.).Domestic Dog Cognition and Behavior. Berlin / Heidelberg: Springer.
^Weiss, E., Kislev, M.E., Simchoni, O. & Nadel, D. Small-grained wild grasses as staple food at the 23000-year-old site of Ohalo IIEconomic Botany 58:s125-s134.
^Harris, David R. (1996).The Origin and Spread of Agriculture and Pastoralism in Eurasia. London: University College London Press. pp. 142–158.ISBN978-1-85728-537-6.
^"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
^Carney, Judith (2009).In the Shadow of Slavery. Berkeley and Los Angeles, California: University of California Press. p. 16.ISBN978-0-520-26996-5.
^Piperno, Dolores R. (October 2011). "The Origins of Plant Cultivation and Domestication in the New World Tropics: Patterns, Process, and New Developments".Current Anthropology.52 (S4):S453–S470.doi:10.1086/659998.S2CID83061925.the Central Balsas River Valley of Mexico, maize's postulated cradle of origin ... dispersed into lower Central America by 7600 BP
^Snir, Ainit and Weiss, Ehud 2014 A novel morphometric method for differentiating wild and domesticated barley through intra-rachis measurements,Journal of Archaeological Science 44: 69–75,https://doi.org/10.1016/j.jas.2014.01.014
^Shao, G.; Tang, A.; Tang, S. Q.; Luo, J.; Jiao, G. A.; Wu, J. L.; Hu, P. S. (April 2011). "A new deletion mutation of the fragrant gene and the development of three molecular markers for fragrance in rice".Plant Breeding. 2.130 (2):172–176.Bibcode:2011PBree.130..172S.doi:10.1111/j.1439-0523.2009.01764.x.
^Berry, R. J. (1969). "The Genetical Implications of Domestication in Animals". In Ucko, Peter J.; Dimbleby, G. W. (eds.).The Domestication and Exploitation of Plants and Animals. Chicago:Aldine. pp. 207–217.
^Heim, Roger (1942). "Nouvelles études descriptives sur les agarics termitophiles d'Afrique tropicale" [New Descriptive Studies on the Termitophile Mushrooms of Tropical Africa].Archives du Muséum National d'Histoire Naturelle (in French).18 (6):107–166.
^It includes "relevant stratigraphy and climate chronologies. For each species, the time periods of significant pre-domestication human–animal interactions are also shown." "Stratigraphy information was obtained from the International Commission on Stratigraphy website. The Quaternary temperature plot was generated from the GISP2 ice core temperature and accumulation data"
Banning, Edward B. (2002). "Aceramic Neolithic". In Peregrine, Peter N.; Ember, Melvin (eds.).Encyclopedia of Prehistory, Volume 8: South and Southwest Asia.Kluwer Academic/Plenum Publishers.
Hare, Brian;Woods, Vanessa (August 2020). "Survival of the Friendliest: Natural selection for hypersocial traits enabled Earth's apex species to best Neandertals and other competitors".Scientific American. Vol. 323, no. 2. pp. 58–63.
![Centres of origin and spread of agriculture in the Neolithic Revolution as understood in 2003[26]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aCentres_of_origin_and_spread_of_agriculture_labelled.svg)
![Rough timelines of domestication for 11 animal species[27][a]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aDomestication_Timeline.jpg)
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