What is domestication?
Authors: Michael D. Purugganan
Journal: Trends in Ecology & Evolution (2022)

The study of domestication has seen enormous strides in recent years, but the concept of domestication has been unclear.The core nature of domestication is as the coevolution between domesticator and domesticate.Evolutionary and ecological studies with both human-associated domestication and non-human domesticators can help us understand the nature of this phenomenon. The nature of domestication is often misunderstood. Most definitions of the process are anthropocentric and center on human intentionality, which minimizes the role of unconscious selection and also excludes non-human domesticators. An overarching, biologically grounded definition of domestication is discussed, which emphasizes its core nature as a coevolutionary process that arises from a specialized mutualism, in which one species controls the fitness of another in order to gain resources and/or services. This inclusive definition encompasses both human-associated domestication of crop plants and livestock as well as other non-human domesticators, such as insects. It also calls into question the idea that humans are themselves domesticated, given that evolution of human traits did not arise through the control of fitness by another species. The nature of domestication is often misunderstood. Most definitions of the process are anthropocentric and center on human intentionality, which minimizes the role of unconscious selection and also excludes non-human domesticators. An overarching, biologically grounded definition of domestication is discussed, which emphasizes its core nature as a coevolutionary process that arises from a specialized mutualism, in which one species controls the fitness of another in order to gain resources and/or services. This inclusive definition encompasses both human-associated domestication of crop plants and livestock as well as other non-human domesticators, such as insects. It also calls into question the idea that humans are themselves domesticated, given that evolution of human traits did not arise through the control of fitness by another species. The domestication of plants and animals by Homo sapiens is thought to be one of the most important developments in the history of humans [1.Diamond J. Evolution, consequences and future of plant and animal domestication.Nature. 2002; 418: 700-707Crossref PubMed Scopus (952) Google Scholar,2.Larson G. et al.Current perspectives and the future of domestication studies.Proc. Natl. Acad. Sci. U. S. A. 2014; 111: 6139-6146Crossref PubMed Scopus (413) Google Scholar]. About 11 000 years ago, at the start of the Holocene (see Glossary), many human societies intensified their transition from hunting and gathering to the cultivation of plants and herding of animals, leading to the domestication of crops and livestock [1.Diamond J. Evolution, consequences and future of plant and animal domestication.Nature. 2002; 418: 700-707Crossref PubMed Scopus (952) Google Scholar,2.Larson G. et al.Current perspectives and the future of domestication studies.Proc. Natl. Acad. Sci. U. S. A. 2014; 111: 6139-6146Crossref PubMed Scopus (413) Google Scholar]. A large component of modern human culture is sustained by the plants and animals that underpin our survival, owing in no small part to the domestication of numerous species undertaken by ancestors of farming/pastoralist societies. It has been observed that 'domestication is one of those terms…long used…[but] struggling to find a satisfactory definition' [3.O'Connor T. Working at relationships: another look at animal domestication.Antiquity. 1997; 71: 149-156Crossref Scopus (70) Google Scholar]. This may come as a surprise, as there is an instinctual consensus on what domesticate species are: the plants and animals found under the care of humans that provide us with benefits and which have evolved under our control. Humans, however, were not the only species associated with domestication and termites, ants, and beetles have been shown to have domesticated various fungal species (Figure 1) [4.Mueller U. et al.The evolution of agriculture in insects.Ann. Rev. Ecol. Evol. Syst. 2005; 36: 563-595Crossref Scopus (401) Google Scholar]. Moreover, the term domestication is sometimes mistakenly applied in relation to entities as diverse as commensal species, weeds, transposable elements, and even humans (Box 1). When one looks carefully at the concept of domestication, and how it differs from other interspecies relationships, one suddenly appreciates how the use of this term can so easily be misdirected.Box 1Ferals, weeds, and other peri-domesticatesA number of species are sometimes referred to as domesticated, even though their fitness is not under the control of a domesticator. In principle, these species are better understood as peri-domesticates (i.e., in the vicinity or fringe of domestication). Peri-domesticates are adapted to living in the environments provided by (or associated with) the domesticator, or are wild species that descended from domesticated taxa.Commensal species are classic examples associated with humans, including house mice and fruit flies, and it is sometimes thought that commensality may have served as an intermediate step towards domestication [25.Larson G. Fuller D.Q. The evolution of animal domestication.Ann. Rev. Ecol. Evol. Syst. 2014; 45: 115-136Crossref Scopus (288) Google Scholar,74.Zeder M.A. The domestication of animals.J. Anthropol. Res. 2012; 68: 161-190Crossref Scopus (211) Google Scholar]. Another category are feral individuals that were once domesticated but have left the mutualism and whose fitness is no longer under the control of the domesticator [75.Gering E. et al.Getting back to nature: feralization in animals and plants.Trends Ecol. Evol. 2019; 34: 1137-1151Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar,76.Mabry M. et al.Feralization: confronting the complexity of domestication and evolution.Trends Genet. 2021; 37: 302-305Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar]. This process has been described as 'de-domestication' [77.Wu D. et al.De-domestication: an extension of crop evolution.Trends Plant Sci. 2021; 26: 560-574Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar] and feral dogs, cats, pigs, and horses are good examples, as are fruit tree species that colonize wild areas or grow in abandoned orchards. Some feral organisms revert completely to the wild, others become commensal, and a few evolve as weeds.Weedy species are a special case of peri-domestication, as these organisms can be considered cheaters within the domestication relationship. Weeds grow and exploit the agricultural environment developed by humans [78.Baker H.G. The evolution of weeds.Annu. Rev. Ecol. Syst. 1974; 5: 1-24Crossref Google Scholar] and, in so doing, negatively impact the fitness of domesticated crop species by competition. Weeds can evolve from wild species, some via Vavilovian or crop mimicry [79.Barrett S. Crop mimicry in weeds.Econ. Bot. 1983; 37: 255-282Crossref Scopus (271) Google Scholar]; examples include false flax (Camelina sativa linicola) that grows in flax fields [79.Barrett S. Crop mimicry in weeds.Econ. Bot. 1983; 37: 255-282Crossref Scopus (271) Google Scholar] and the Echinochloa sp. barnyard grasses that compete with rice [80.Guo L. et al.Echinochloa crus-galli genome analysis provides insight into its adaptation and invasiveness as a weed.Nat. Comm. 2017; 8: 1031Crossref PubMed Scopus (84) Google Scholar]. Others, such as weedy rice [81.Li L. et al.Signatures of adaptation in the weedy rice genome.Nat. Genet. 2017; 49: 811-814Crossref PubMed Scopus (99) Google Scholar], evolve as ferals from crops. Weedy species are not confined to human-associated domestication, as attine ants have been shown to identify and remove the microfungi Escovopsis sp. from their fungal gardens [82.Currie C. et al.The agricultural pathology of ant fungus gardens.Proc. Natl Acad. Sci. USA. 1999; 96: 7998-8002Crossref PubMed Scopus (315) Google Scholar,83.Currie C. Stuart A. Weeding and grooming of pathogens in agriculture by ants.Proc. R. Soc. Lond. Ser. B. 2001; 268: 1033-1039Crossref PubMed Scopus (229) Google Scholar]. In all these cases, the continued growth and survival of the weedy species depends on it evading domesticator control and their proliferation reduces fitness of both domesticator and domesticate.One should note that there are also examples of species, such as epazote (Chenopodium ambrosioides) [84.Blanckaert I. et al.Ethnobotanical, morphological, phytochemical and molecular evidence for the incipient domestication of epazote (Chenopodium ambrosioides L.: Chenopodiaceae) in a semi-arid region of Mexico.Genet. Res. Crop Evol. 2012; 59: 557-573Crossref Scopus (18) Google Scholar] and columnar cacti (Escontria chiotilla and Polaskia chichipe) [85.Casas A. et al.In situ management and domestication of plants in Mesoamerica.Ann. Bot. 2007; 100: 1101-1115Crossref PubMed Scopus (206) Google Scholar] in Mexico, that are described as weedy, but studies suggest they have been subjected to human management and selection. Although not quite domesticate species, these illustrate how weedy species (and indeed other peri-domesticates) can become subject to increasing human intervention in their life cycles and possibly cross the threshold into domestication. A number of species are sometimes referred to as domesticated, even though their fitness is not under the control of a domesticator. In principle, these species are better understood as peri-domesticates (i.e., in the vicinity or fringe of domestication). Peri-domesticates are adapted to living in the environments provided by (or associated with) the domesticator, or are wild species that descended from domesticated taxa. Commensal species are classic examples associated with humans, including house mice and fruit flies, and it is sometimes thought that commensality may have served as an intermediate step towards domestication [25.Larson G. Fuller D.Q. The evolution of animal domestication.Ann. Rev. Ecol. Evol. Syst. 2014; 45: 115-136Crossref Scopus (288) Google Scholar,74.Zeder M.A. The domestication of animals.J. Anthropol. Res. 2012; 68: 161-190Crossref Scopus (211) Google Scholar]. Another category are feral individuals that were once domesticated but have left the mutualism and whose fitness is no longer under the control of the domesticator [75.Gering E. et al.Getting back to nature: feralization in animals and plants.Trends Ecol. Evol. 2019; 34: 1137-1151Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar,76.Mabry M. et al.Feralization: confronting the complexity of domestication and evolution.Trends Genet. 2021; 37: 302-305Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar]. This process has been described as 'de-domestication' [77.Wu D. et al.De-domestication: an extension of crop evolution.Trends Plant Sci. 2021; 26: 560-574Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar] and feral dogs, cats, pigs, and horses are good examples, as are fruit tree species that colonize wild areas or grow in abandoned orchards. Some feral organisms revert completely to the wild, others become commensal, and a few evolve as weeds. Weedy species are a special case of peri-domestication, as these organisms can be considered cheaters within the domestication relationship. Weeds grow and exploit the agricultural environment developed by humans [78.Baker H.G. The evolution of weeds.Annu. Rev. Ecol. Syst. 1974; 5: 1-24Crossref Google Scholar] and, in so doing, negatively impact the fitness of domesticated crop species by competition. Weeds can evolve from wild species, some via Vavilovian or crop mimicry [79.Barrett S. Crop mimicry in weeds.Econ. Bot. 1983; 37: 255-282Crossref Scopus (271) Google Scholar]; examples include false flax (Camelina sativa linicola) that grows in flax fields [79.Barrett S. Crop mimicry in weeds.Econ. Bot. 1983; 37: 255-282Crossref Scopus (271) Google Scholar] and the Echinochloa sp. barnyard grasses that compete with rice [80.Guo L. et al.Echinochloa crus-galli genome analysis provides insight into its adaptation and invasiveness as a weed.Nat. Comm. 2017; 8: 1031Crossref PubMed Scopus (84) Google Scholar]. Others, such as weedy rice [81.Li L. et al.Signatures of adaptation in the weedy rice genome.Nat. Genet. 2017; 49: 811-814Crossref PubMed Scopus (99) Google Scholar], evolve as ferals from crops. Weedy species are not confined to human-associated domestication, as attine ants have been shown to identify and remove the microfungi Escovopsis sp. from their fungal gardens [82.Currie C. et al.The agricultural pathology of ant fungus gardens.Proc. Natl Acad. Sci. USA. 1999; 96: 7998-8002Crossref PubMed Scopus (315) Google Scholar,83.Currie C. Stuart A. Weeding and grooming of pathogens in agriculture by ants.Proc. R. Soc. Lond. Ser. B. 2001; 268: 1033-1039Crossref PubMed Scopus (229) Google Scholar]. In all these cases, the continued growth and survival of the weedy species depends on it evading domesticator control and their proliferation reduces fitness of both domesticator and domesticate. One should note that there are also examples of species, such as epazote (Chenopodium ambrosioides) [84.Blanckaert I. et al.Ethnobotanical, morphological, phytochemical and molecular evidence for the incipient domestication of epazote (Chenopodium ambrosioides L.: Chenopodiaceae) in a semi-arid region of Mexico.Genet. Res. Crop Evol. 2012; 59: 557-573Crossref Scopus (18) Google Scholar] and columnar cacti (Escontria chiotilla and Polaskia chichipe) [85.Casas A. et al.In situ management and domestication of plants in Mesoamerica.Ann. Bot. 2007; 100: 1101-1115Crossref PubMed Scopus (206) Google Scholar] in Mexico, that are described as weedy, but studies suggest they have been subjected to human management and selection. Although not quite domesticate species, these illustrate how weedy species (and indeed other peri-domesticates) can become subject to increasing human intervention in their life cycles and possibly cross the threshold into domestication. There is certainly no lack of attempts to define domestication and tease apart its core characteristics and there have been several discussions on differing approaches to defining this process [3.O'Connor T. Working at relationships: another look at animal domestication.Antiquity. 1997; 71: 149-156Crossref Scopus (70) Google Scholar,5.Bökönyi S. Definitions of domestication.in: Clutton-Brock J. The Walking Larder: Patterns of Domestication, Pastoralism, and Predation. Routledge, 1989: 1-4Google Scholar, 6.Stetter M. et al.How to make a domesticate.Curr. Biol. 2017; 27: R896-R900Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar, 7.Zeder M.A. Core questions in domestication research.Proc. Natl. Acad. Sci. U. S. A. 2015; 112: 3191-3198Crossref PubMed Scopus (264) Google Scholar, 8.Zeder M.A. Domestication: definition and overview.in: Smith C. Encyclopedia of Global Archaeology. Springer, 2014: 2184-2194Crossref Google Scholar, 9.Bates J. Is domestication speciation? The implications of a messy domestication model in the Holocene.Agronomy. 2021; 11: 784Crossref Scopus (1) Google Scholar, 10.Schultz T. The Convergent Evolution of Agriculture in Humans and Insects. MIT Press, 2021Google Scholar]. Previous definitions of domestication may (or may not) include: (i) the idea of evolutionary change; (ii) control of the process by humans, including the invocation of human intentionality; (iii) the concept of mutualism; (iv) benefits derived by humans; (v) the action of artificial selection; and (vi) enumeration of common domesticate phenotypes [3.O'Connor T. Working at relationships: another look at animal domestication.Antiquity. 1997; 71: 149-156Crossref Scopus (70) Google Scholar,5.Bökönyi S. Definitions of domestication.in: Clutton-Brock J. The Walking Larder: Patterns of Domestication, Pastoralism, and Predation. Routledge, 1989: 1-4Google Scholar, 6.Stetter M. et al.How to make a domesticate.Curr. Biol. 2017; 27: R896-R900Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar, 7.Zeder M.A. Core questions in domestication research.Proc. Natl. Acad. Sci. U. S. A. 2015; 112: 3191-3198Crossref PubMed Scopus (264) Google Scholar, 8.Zeder M.A. Domestication: definition and overview.in: Smith C. Encyclopedia of Global Archaeology. Springer, 2014: 2184-2194Crossref Google Scholar, 9.Bates J. Is domestication speciation? The implications of a messy domestication model in the Holocene.Agronomy. 2021; 11: 784Crossref Scopus (1) Google Scholar, 10.Schultz T. The Convergent Evolution of Agriculture in Humans and Insects. MIT Press, 2021Google Scholar]. These past definitions have their strengths but also crucial shortcomings. Many, for example, privilege a human-centered conception of domestication [5.Bökönyi S. Definitions of domestication.in: Clutton-Brock J. The Walking Larder: Patterns of Domestication, Pastoralism, and Predation. Routledge, 1989: 1-4Google Scholar,11.Clutton-Brock J. The unnatural world: behavioural aspects of humans and animals in the process of domestication.in: Manning A. Serpell J. Animals and Human Society: Changing Perspectives. Routledge, 1994: 23-35Google Scholar], which minimizes its biological context while also marginalizing non-human domesticators [6.Stetter M. et al.How to make a domesticate.Curr. Biol. 2017; 27: R896-R900Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar]. There are definitions in which domestication is narrowly described as the control of the domesticate by the domesticator, devaluing the reciprocal nature of the ecological interaction. And for definitions that rely on a checklist of specific traits/phenotypes (referred to as the domestication syndrome) [12.Hammer K. Das Domestikationssyndrom.Kulturpflanze. 1984; 32: 11-34Crossref Scopus (332) Google Scholar,13.Clutton-Brock J. A Natural History of Domesticated Mammals. Cambridge, 1999Google Scholar], these conflate the outcome (domestication traits and species) with the process (domestication) and are relevant to only a handful of cases. In crafting a definition of domestication, the thoughtful analysis provided by Zeder [7.Zeder M.A. Core questions in domestication research.Proc. Natl. Acad. Sci. U. S. A. 2015; 112: 3191-3198Crossref PubMed Scopus (264) Google Scholar], whose own definition leans heavily on ideas by Rindos and others [14.Rindos D. The Origins of Agriculture: An Evolutionary Perspective. Academic Press, 1984Google Scholar, 15.Rindos D. Symbiosis, instability, and the origins and spread of agriculture: a new model.Curr. Anthropol. 1980; 21: 751-772Crossref Scopus (110) Google Scholar, 16.Blumler M. Byrne R. The ecological genetics of domestication and the origins of agriculture.Curr. Anthropol. 1991; 32: 23-54Crossref Google Scholar, 17.Harlan J.R. et al.Comparative evolution of cereals.Evolution. 1973; 27: 311-325Crossref PubMed Google Scholar, 18.Smith B.D. Low-level food production.J. Archaeol. Res. 2001; 9: 1-43Crossref Scopus (442) Google Scholar], can serve as a starting point. Synthesizing these and other perspectives [3.O'Connor T. Working at relationships: another look at animal domestication.Antiquity. 1997; 71: 149-156Crossref Scopus (70) Google Scholar,5.Bökönyi S. Definitions of domestication.in: Clutton-Brock J. The Walking Larder: Patterns of Domestication, Pastoralism, and Predation. Routledge, 1989: 1-4Google Scholar,6.Stetter M. et al.How to make a domesticate.Curr. Biol. 2017; 27: R896-R900Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar,8.Zeder M.A. Domestication: definition and overview.in: Smith C. Encyclopedia of Global Archaeology. Springer, 2014: 2184-2194Crossref Google Scholar, 9.Bates J. Is domestication speciation? The implications of a messy domestication model in the Holocene.Agronomy. 2021; 11: 784Crossref Scopus (1) Google Scholar, 10.Schultz T. The Convergent Evolution of Agriculture in Humans and Insects. MIT Press, 2021Google Scholar], a broad biological definition of domestication is that it is a coevolutionary process that arises from a mutualism, in which one species (the domesticator) constructs an environment where it actively manages both the survival and reproduction of another species (the domesticate) in order to provide the former with resources and/or services (Figure 2). This allows for increased fitness for the interacting organisms within the mutualistic relationship, leading to the evolution of traits that ensures the stable association of domesticator and domesticate across generations. This biological definition has several advantages. It firmly centers domestication as an explicitly evolutionary process that arises from an ecological interaction (mutualism) [3.O'Connor T. Working at relationships: another look at animal domestication.Antiquity. 1997; 71: 149-156Crossref Scopus (70) Google Scholar,7.Zeder M.A. Core questions in domestication research.Proc. Natl. Acad. Sci. U. S. A. 2015; 112: 3191-3198Crossref PubMed Scopus (264) Google Scholar,14.Rindos D. The Origins of Agriculture: An Evolutionary Perspective. Academic Press, 1984Google Scholar, 15.Rindos D. Symbiosis, instability, and the origins and spread of agriculture: a new model.Curr. Anthropol. 1980; 21: 751-772Crossref Scopus (110) Google Scholar, 16.Blumler M. Byrne R. The ecological genetics of domestication and the origins of agriculture.Curr. Anthropol. 1991; 32: 23-54Crossref Google Scholar, 17.Harlan J.R. et al.Comparative evolution of cereals.Evolution. 1973; 27: 311-325Crossref PubMed Google Scholar, 18.Smith B.D. Low-level food production.J. Archaeol. Res. 2001; 9: 1-43Crossref Scopus (442) Google Scholar, 19.Spengler R.N. Anthropogenic seed dispersal: rethinking the origins of plant domestication.Trends Plant Sci. 2020; 25: 340-348Abstract Full Text Full Text PDF PubMed Scopus (25) Google Scholar, 20.Jones G. et al.The origins of agriculture: intentions and consequences.J. Archaeol. Sci. 2021; 125105290Crossref PubMed Scopus (9) Google Scholar]. This definition incorporates the language of fitness components (survival and reproduction) and highlights the niche construction role of the domesticator [21.Zeder M. Domestication as a model system for niche construction theory.Evol. Ecol. 2016; 30: 325-348Crossref Scopus (96) Google Scholar,22.Smith B.D. Niche constriction and the behavioral context of plant and animal domestication.Evol. Anthropol. 2007; 16: 188-199Crossref Scopus (183) Google Scholar]. Unlike Zeder, however, it does not attribute the goal of the process as providing a more predictable resource supply to the domesticator [7.Zeder M.A. Core questions in domestication research.Proc. Natl. Acad. Sci. U. S. A. 2015; 112: 3191-3198Crossref PubMed Scopus (264) Google Scholar], which may not be clearly applicable across all instances of domestication. Finally, this conception of domestication is agnostic to the identities of the interacting species and to the precise mechanisms by which the mutualism is established and stabilized by coevolution. The interactions associated with domestication are similar to other mutualisms, but with two key differences. First, unlike other mutualisms, the domesticator establishes the environment where it actively controls the fitness (survival and reproduction) of the domesticate. Second, this control is exerted by the domesticator primarily so it can utilize the resources or services provided by the domesticate. This biological conceptualization of domestication also raises the question of when to consider a species as 'domesticated' or as a 'domesticate species'. The term may be appropriately reserved for those species that have evolved to specialize in thriving under the active management of the domesticator and therefore become dependent on the latter as opposed to living in the wild. The issue, however, as to what threshold of evolutionary transformation and dependency a species must cross before they can be recognized as a domesticate, needs more scrutiny. Of all the examples of domestication, human-associated domestication is undoubtedly the best known, not least of which is because of its central role in the ecology of modern H. sapiens [1.Diamond J. Evolution, consequences and future of plant and animal domestication.Nature. 2002; 418: 700-707Crossref PubMed Scopus (952) Google Scholar,2.Larson G. et al.Current perspectives and the future of domestication studies.Proc. Natl. Acad. Sci. U. S. A. 2014; 111: 6139-6146Crossref PubMed Scopus (413) Google Scholar,23.Purugganan M.D. Fuller D.Q. The nature of selection during plant domestication.Nature. 2009; 457: 843-848Crossref PubMed Scopus (590) Google Scholar, 24.Meyer R.S. Purugganan M.D. Evolution of crop species: genetics of domestication and diversification.Nat. Rev. Genet. 2013; 14: 840-852Crossref PubMed Scopus (600) Google Scholar, 25.Larson G. Fuller D.Q. The evolution of animal domestication.Ann. Rev. Ecol. Evol. Syst. 2014; 45: 115-136Crossref Scopus (288) Google Scholar]. Most human-associated domestication began in earnest starting in the Holocene about 11 000 YBP, when humans in different parts of the world transformed their behavioral ecology of food acquisition from largely hunting and foraging to controlling the survival and reproduction of heretofore wild populations by cultivation, herding, and animal husbandry. This transition began the process of domestication; in food plants, for example, the annual cycles of sowing, harvesting, and processing by humans led to novel selection pressures that over the next 2000-4000 years eventually led to crop domestication [14.Rindos D. The Origins of Agriculture: An Evolutionary Perspective. Academic Press, 1984Google Scholar, 15.Rindos D. Symbiosis, instability, and the origins and spread of agriculture: a new model.Curr. Anthropol. 1980; 21: 751-772Crossref Scopus (110) Google Scholar, 16.Blumler M. Byrne R. The ecological genetics of domestication and the origins of agriculture.Curr. Anthropol. 1991; 32: 23-54Crossref Google Scholar,23.Purugganan M.D. Fuller D.Q. The nature of selection during plant domestication.Nature. 2009; 457: 843-848Crossref PubMed Scopus (590) Google Scholar]. It is estimated humans have domesticated about >1000 plant [26.Milla R. et al.Phylogenetic patterns and phenotypic profiles of the species of plants and mammals farmed for food.Nat. Ecol. Evol. 2018; 2: 1808-1817Crossref PubMed Scopus (36) Google Scholar,27.Meyer R. et al.Patterns and processes in crop domestication: an historical review and quantitative analysis of 203 global food crops.New Phytol. 2012; 196: 29-48Crossref PubMed Scopus (472) Google Scholar] and possibly around 40–50 animal (i.e., mammal, bird, fish, and insect) species [28.Ahmad H. et al.The domestication makeup: evolution, survival, and challenges.Front. Ecol. Evol. 2020; 8: 103Crossref Scopus (15) Google Scholar], as well as about a dozen fungal and bacterial species [29.Douglas G.L. Klaenhammer T.R. Genomic evolution of domesticated microorganisms.Ann. Rev. Food Sci. Technol. 2010; 1: 397-414Crossref PubMed Scopus (53) Google Scholar]. While food remains the primary resource that domesticate species supply to humans, these mutualistic taxa also provide material (e.g., cotton, flax, silk) and services (e.g. sentry duty and hunting by dogs [30.Driscoll C.A. et al.From wild animals to domestic pets, an evolutionary view of domestication.Proc. Natl Acad. Sci. USA. 2009; 106: 9971-9978Crossref PubMed Scopus (315) Google Scholar], transport by horses, and mouse eradication by cats [31.Cucchi T. et al.Tracking the Near Eastern origins and European dispersal of the western house mouse.Sci. Rep. 2020; 10: 8276Crossref PubMed Scopus (29) Google Scholar]) to H. sapiens (but see Box 2).Box 2Why domesticate flowers?There is a long history of the cultivation of plants for ornamental purposes, in the Fertile Crescent, China, Mexico, and South America, including the maintenance of pleasure gardens [86.Gessert G. Green Light: Toward an Art of Evolution. MIT Press, 2010Crossref Google Scholar]. Moreover, the presence of floral ornaments and plants in various tombs (including with Egyptian pharaohs 3300 years ago [87.Hepper F.N. Pharaoh's Flowers: The Botanical Treasures of Tutankhamun. KWS Publishers, 2009Google Scholar] and a Natufian grave before 11 700 years ago [88.Nadel D. et al.Earliest floral grave lining from 13,700- 11,700-y-old Natufian burials at Raqefet cave, Mt. Carmel, Israel.Proc. Natl. Acad. Sci. U. S. A. 2013; 110: 11744-11778Crossref Scopus (62) Google Scholar]) are indications that these ornamental plants were possibly imbued with symbolic and religious significance.The domestication of floral crops and other ornamental species that are selected and maintained for aesthetic purposes (Figure I) presents a special difficulty in our understanding of domestication. Unlike food plants, these ornamentals are usually selected for sensory traits that include flower and/or leaf color, leaf shape, fragrance, leaf texture and variegation, and overall plant form [89.Altman A. et al.Ornamental plant domestication by aesthetics-driven human cultural niche construction.Trends Plant Sci. 2021; 27: 124-138Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar]; most were domesticated only in the last 500 years [86.Gessert G. Green Light: Toward an Art of Evolution. MIT Press, 2010Crossref Google Scholar]. The conundrum of the domestication of ornamental plants rests on why they were domesticated and what fitness advantage they confer on their human domesticators.There are several possibilities. First, many of these may have been initially domesticated for other purposes, for food or medici