Title: Domestication syndrome

{{short description|Proposed biological phenomenon}}

[[File:Unnatural selection, 2 heads, one species.jpg|thumb|right|Reduction in size is regarded as a domestication syndrome trait - [[grey wolf]] skull compared with a [[Chihuahua (dog)|chihuahua]] skull]]

'''Domestication syndrome''' refers to two sets of [[phenotypic]] traits that are common to either [[domesticated plant]]s&lt;ref name=&quot;:11&quot; /&gt;&lt;ref name=&quot;:12&quot; /&gt; or [[domestication of animals|domesticated animals]].&lt;ref name=&quot;:0&quot;&gt;{{Cite journal |last1=Wilkins |first1=Adam S |last2=Wrangham |first2=Richard W |last3=Fitch |first3=W Tecumseh |date=2014-07-01 |title=The &quot;Domestication Syndrome&quot; in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics |journal=Genetics |language=en |volume=197 |issue=3 |pages=795–808 |doi=10.1534/genetics.114.165423 |issn=1943-2631 |pmc=4096361 |pmid=25024034}}&lt;/ref&gt;

Domesticated animals tend to be smaller and less aggressive than their wild counterparts; they may also have floppy ears, variations to coat color, a smaller brain, and a shorter muzzle. Other traits may include changes in the endocrine system and an extended breeding cycle.&lt;ref name=&quot;:0&quot; /&gt;&lt;ref name=&quot;:3&quot; /&gt;&lt;ref name=&quot;:2&quot; /&gt; These animal traits have been claimed to emerge across the different species in response to selection for tameness, which was purportedly demonstrated in a [[Domesticated silver fox|famous Russian fox breeding experiment]],&lt;ref name=&quot;:7&quot; /&gt;&lt;ref name=&quot;:8&quot; /&gt;&lt;ref name=&quot;:9&quot; /&gt; though this claim has been disputed.&lt;ref name=&quot;:10&quot; /&gt;&lt;ref name=&quot;:1&quot; /&gt;

Other research&lt;ref name=&quot;:0&quot; /&gt; suggested that [[Pleiotropy|pleiotropic]] change in  [[neural crest]] cell regulating genes was the common cause of shared traits seen in many domesticated animal species. However, several recent publications have either questioned this neural crest cell explanation&lt;ref name=&quot;:3&quot;&gt;{{Cite journal |last1=Wright |first1=Dominic |last2=Henriksen |first2=Rie |last3=Johnsson |first3=Martin |date=2020 |title=Defining the Domestication Syndrome: Comment on Lord et al. 2020 |url=https://linkinghub.elsevier.com/retrieve/pii/S016953472030224X |journal=Trends in Ecology &amp; Evolution |language=en |volume=35 |issue=12 |pages=1059–1060 |doi=10.1016/j.tree.2020.08.009|pmid=32917395 |bibcode=2020TEcoE..35.1059W |s2cid=221636622 |url-access=subscription }}&lt;/ref&gt;&lt;ref name=&quot;:4&quot;&gt;{{Cite journal |last1=Johnsson |first1=Martin |last2=Henriksen |first2=Rie |last3=Wright |first3=Dominic |date=2021-08-26 |editor-last=Peichel |editor-first=C L |title=The neural crest cell hypothesis: no unified explanation for domestication |url=https://academic.oup.com/genetics/article/doi/10.1093/genetics/iyab097/6318714 |journal=Genetics |language=en |volume=219 |issue=1 |doi=10.1093/genetics/iyab097 |issn=1943-2631 |pmc=8633120 |pmid=34849908}}&lt;/ref&gt;&lt;ref name=&quot;:1&quot; /&gt; or cast doubt on the existence of domestication syndrome itself.&lt;ref name=&quot;:10&quot;&gt;{{Cite journal |last1=Lord |first1=Kathryn A. |last2=Larson |first2=Greger |last3=Coppinger |first3=Raymond P. |last4=Karlsson |first4=Elinor K. |date=February 2020 |title=The History of Farm Foxes Undermines the Animal Domestication Syndrome |journal=Trends in Ecology &amp; Evolution |language=en |volume=35 |issue=2 |pages=125–136 |doi=10.1016/j.tree.2019.10.011|pmid=31810775 |doi-access=free |bibcode=2020TEcoE..35..125L }}&lt;/ref&gt; One recent publication&lt;ref name=&quot;:1&quot;&gt;{{Cite journal |last1=Gleeson |first1=Ben Thomas |last2=Wilson |first2=Laura A. B. |date=2023-03-29 |title=Shared reproductive disruption, not neural crest or tameness, explains the domestication syndrome |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=290 |issue=1995 |doi=10.1098/rspb.2022.2464 |issn=0962-8452 |pmc=10031412 |pmid=36946116}}&lt;/ref&gt; points out that shared selective regime changes following transition from wild to domestic environments are a more likely cause of any convergent traits. In addition, the sheer number, diversity, and phenotypic importance of neural crest cell-derived vertebrate features means that changes in genes associated with them are almost inevitable in response to any significant selective change.&lt;ref name=&quot;:1&quot; /&gt;  

A significant aspect of domestication syndrome is prolonged juvenile behavior/traits. A universal problem with the keeping of tame wild animals is the eventual, inevitable adulthood and behavioral difficulties thereof. Toy/teacup breed animals may be considered the furthest extreme aspect of this, as they are essentially juveniles their entire lives (to the point where breeding them is a complex, delicate matter, and survival of the infants is lowered).{{Citation needed|date=October 2025}}

The process of [[plant domestication]] has produced changes in [[shattering (agriculture)|shattering]]/fruit [[abscission]], shorter height, larger [[grain]] or fruit size, easier [[threshing]], [[synchronous flowering]], and increased yield, as well as changes in color, taste, and texture.&lt;ref name=&quot;Kantar-et-al-2016&quot;&gt;{{cite journal |last1=Kantar |first1=Michael B. |last2=Tyl |first2=Catrin E. |last3=Dorn |first3=Kevin M. |last4=Zhang |first4=Xiaofei |last5=Jungers |first5=Jacob M. |last6=Kaser |first6=Joe M. |last7=Schendel |first7=Rachel R. |last8=Eckberg |first8=James O. |last9=Runck |first9=Bryan C. |last10=Bunzel |first10=Mirko |last11=Jordan |first11=Nick R. |last12=Stupar |first12=Robert M. |last13=Marks |first13=M. David |last14=Anderson |first14=James A. |last15=Johnson |first15=Gregg A. |date=2016-04-29 |title=Perennial Grain and Oilseed Crops |journal=[[Annual Review of Plant Biology]] |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |volume=67 |issue=1 |pages=703–29 |doi=10.1146/annurev-arplant-043015-112311 |issn=1543-5008 |pmid=26789233 |doi-access=free |last16=Sheaffer |first16=Craig C. |last17=Schoenfuss |first17=Tonya C. |last18=Ismail |first18=Baraem |last19=Heimpel |first19=George E. |last20=Wyse |first20=Donald L.|bibcode=2016AnRPB..67..703K }}{{rp|page=708}}&lt;/ref&gt;

== Origin ==

{{Dark mode invert|[[File:Traits Defining Domestication Syndrome.jpg|thumb|In ten publications on domestication syndrome in animals, no single trait is included in every one.&lt;ref name=Lord2019/&gt;]]}}

[[Charles Darwin]]'s study of ''[[The Variation of Animals and Plants Under Domestication]]'' in 1868 identified various behavioral, morphological, and physiological traits that are shared by domestic animals, but not by their wild ancestors. These shared traits became known as &quot;the domestication syndrome&quot;,&lt;ref name=&quot;:0&quot; /&gt; a term originally used to describe common changes in domesticated grains.&lt;ref name=&quot;:11&quot;&gt;{{Cite journal |last1=Harlan |first1=Jack R. |last2=de Wet |first2=J. M. J. |last3=Price |first3=E. Glen |date=1973 |title=Comparative Evolution of Cereals |journal=Evolution |volume=27 |issue=2 |pages=311–325 |doi=10.2307/2406971|jstor=2406971 |pmid=28564784 }}&lt;/ref&gt;&lt;ref name=&quot;:12&quot;&gt;{{Cite journal |last=Hammer |first=Karl |date=June 1984 |title=Das Domestikationssyndrom |url=http://link.springer.com/10.1007/BF02098682 |journal=Die Kulturpflanze |language=de |volume=32 |issue=1 |pages=11–34 |doi=10.1007/BF02098682 |s2cid=42389667 |issn=0075-7209|url-access=subscription }}&lt;/ref&gt; In animals, these traits include tameness, docility, floppy ears, altered tails, novel coat colors and patterns, reduced brain size, reduced body mass and smaller teeth.&lt;ref name=&quot;:0&quot; /&gt;&lt;ref name=&quot;:3&quot; /&gt;&lt;ref name=&quot;:2&quot;&gt;{{Cite journal |last1=Sánchez-Villagra |first1=Marcelo R. |last2=Geiger |first2=Madeleine |last3=Schneider |first3=Richard A. |date=June 2016 |title=The taming of the neural crest: a developmental perspective on the origins of morphological covariation in domesticated mammals |journal=Royal Society Open Science |language=en |volume=3 |issue=6 |article-number=160107 |doi=10.1098/rsos.160107 |issn=2054-5703 |pmc=4929905 |pmid=27429770|bibcode=2016RSOS....360107S }}&lt;/ref&gt; Other traits include changes in craniofacial morphology, alterations to the endocrine system, and changes to the female estrous cycles including the ability to breed all year-round.&lt;ref name=&quot;:0&quot; /&gt;&lt;ref name=&quot;:2&quot; /&gt;&lt;ref name=machugh2016/&gt;

A recent hypothesis suggests that [[neural crest]] cell behaviour may be modified by domestication, which then leads to those traits that are common across many domesticated animal species.&lt;ref name=&quot;:0&quot; /&gt;&lt;ref&gt;{{Cite journal |last=Wilkins |first=Adam S. |date=January 2020 |title=A striking example of developmental bias in an evolutionary process: The &quot;domestication syndrome&quot; |url=https://onlinelibrary.wiley.com/doi/10.1111/ede.12319 |journal=Evolution &amp; Development |language=en |volume=22 |issue=1–2 |pages=143–153 |doi=10.1111/ede.12319 |pmid=31545016 |issn=1520-541X|url-access=subscription }}&lt;/ref&gt;&lt;ref name=&quot;:6&quot;&gt;{{Cite journal |last1=Wilkins |first1=Adam S |last2=Wrangham |first2=Richard |last3=Fitch |first3=W Tecumseh |date=2021-08-26 |editor-last=Peichel |editor-first=C L |title=The neural crest/domestication syndrome hypothesis, explained: reply to Johnsson, Henriksen, and Wright |url=https://academic.oup.com/genetics/article/doi/10.1093/genetics/iyab098/6323656 |journal=Genetics |language=en |volume=219 |issue=1 |doi=10.1093/genetics/iyab098 |issn=1943-2631 |pmc=8633094 |pmid=34849912}}&lt;/ref&gt; This hypothesis has claimed support from many gene-based studies; e.g.,&lt;ref&gt;{{Cite journal |last1=Librado |first1=Pablo |last2=Gamba |first2=Cristina |last3=Gaunitz |first3=Charleen |last4=Der Sarkissian |first4=Clio |last5=Pruvost |first5=Mélanie |last6=Albrechtsen |first6=Anders |last7=Fages |first7=Antoine |last8=Khan |first8=Naveed |last9=Schubert |first9=Mikkel |last10=Jagannathan |first10=Vidhya |last11=Serres-Armero |first11=Aitor |last12=Kuderna |first12=Lukas F. K. |last13=Povolotskaya |first13=Inna S. |last14=Seguin-Orlando |first14=Andaine |last15=Lepetz |first15=Sébastien |date=2017-04-28 |title=Ancient genomic changes associated with domestication of the horse |url=https://www.science.org/doi/10.1126/science.aam5298 |journal=Science |language=en |volume=356 |issue=6336 |pages=442–445 |doi=10.1126/science.aam5298 |pmid=28450643 |bibcode=2017Sci...356..442L |s2cid=206656021 |issn=0036-8075|url-access=subscription }}&lt;/ref&gt;&lt;ref name=&quot;:5&quot;&gt;{{Cite journal |last1=Pendleton |first1=Amanda L. |last2=Shen |first2=Feichen |last3=Taravella |first3=Angela M. |last4=Emery |first4=Sarah |last5=Veeramah |first5=Krishna R. |last6=Boyko |first6=Adam R. |last7=Kidd |first7=Jeffrey M. |date=December 2018 |title=Comparison of village dog and wolf genomes highlights the role of the neural crest in dog domestication |journal=BMC Biology |language=en |volume=16 |issue=1 |page=64 |doi=10.1186/s12915-018-0535-2 |doi-access=free |issn=1741-7007 |pmc=6022502 |pmid=29950181}}&lt;/ref&gt; However, recent publications have disputed this support; pointing out that observed change in neural crest related genes only reveals change in neural crest-derived features.&lt;ref name=&quot;:3&quot; /&gt;&lt;ref name=&quot;:4&quot; /&gt; In effect, it is not evidence of linked trait changes in different species due to pleiotropic neural crest mechanisms as claimed by the neural crest cell hypothesis.&lt;ref name=&quot;:0&quot; /&gt; For example, all of the craniofacial skeleton is derived from the neural crest, so any animal population that experiences evolutionary change in craniofacial features will show changes in genes associated with the neural crest. The number and importance of neural crest cell features in all vertebrates means change in these features is almost inevitable under the major selective regime shifts experienced by animals making the wild to domestic transition.&lt;ref name=&quot;:1&quot; /&gt;

== Cause ==

Many similar traits – both in animals and plants – are produced by [[ortholog]]s; however, whether this is true for domestication traits or merely for wild forms is less clear. Especially in the case of plant [[crop]]s, doubt has been cast because some domestication traits have been found to result from unrelated [[locus (genetics)|loci]].&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt; 

In 2018, a study identified 429 genes that differed between modern dogs and modern wolves. As the differences in these genes could also be found in ancient dog fossils, these were regarded as being the result of the initial domestication and not from recent breed formation. These genes are linked to [[neural crest]] and [[central nervous system]] development. These genes affect [[embryogenesis]] and can confer tameness, smaller jaws, floppy ears, and diminished craniofacial development, which distinguish domesticated dogs from wolves and are considered to reflect domestication syndrome. The study concluded that during early dog domestication, the initial selection was for behavior. This trait is influenced by those genes which act in the neural crest, which led to the phenotypes observed in modern dogs.&lt;ref name=&quot;:5&quot; /&gt;

The 2023 [[Parasite-stress theory|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 [[microRNA]]s. 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.&lt;ref name=&quot;Skok 2023a&quot;&gt;{{cite journal |last=Skok |first=J. |date=2023a |title=The Parasite-Mediated Domestication Hypothesis |journal=Agricultura Scientia |doi=10.18690/agricsci.20.1.1 |volume=20 |issue=1 |pages=1–7 |doi-access=free}}&lt;/ref&gt;&lt;ref name=&quot;Skok 2023b&quot;&gt;{{Cite journal |last=Skok|first=J. |date=2023b |title=Addendum to &quot;The parasite-mediated domestication hypothesis&quot; |journal=OSF |doi=10.31219/osf.io/f92aj |doi-access=free}}&lt;/ref&gt;

== In animals ==

A dog's cranium is 15% smaller than an equally heavy wolf's, and the dog is less aggressive and more playful. Other species pairs show similar differences. [[Bonobo]]s, like [[chimpanzee]]s, are a close genetic cousin to humans, but unlike the chimpanzees, bonobos are not aggressive and do not participate in lethal inter-group aggression or kill within their own group. The most distinctive features of a bonobo are its cranium, which is 15% smaller than a chimpanzee's, and its less aggressive and more playful behavior. These, and other, features led to the proposal that bonobos are a 'self-domesticated' ape.&lt;ref name=&quot;hareb2013&quot; /&gt;&lt;ref&gt;{{Cite journal |last1=Hare |first1=Brian |last2=Wobber |first2=Victoria |last3=Wrangham |first3=Richard |date=March 2012 |title=The self-domestication hypothesis: evolution of bonobo psychology is due to selection against aggression |url=https://linkinghub.elsevier.com/retrieve/pii/S000334721100546X |journal=Animal Behaviour |language=en |volume=83 |issue=3 |pages=573–585 |doi=10.1016/j.anbehav.2011.12.007|s2cid=3415520 |url-access=subscription }}&lt;/ref&gt; In other examples, the [[guinea pig]]'s cranium is 13% smaller than its wild cousin the [[cavy]], and domestic fowl show a similar reduction to their wild cousins. In a famous Russian farm fox experiment, foxes selectively bred for reduced aggression appeared to show other traits associated with domestication syndrome. This prompted the claim that domestication syndrome was caused by selection for tameness. The foxes were not selectively bred for smaller craniums and teeth, floppy ears, or skills at using human gestures, but these traits were demonstrated in the friendly foxes. Natural selection favors those that are the most successful at reproducing, not the most aggressive. Selection against aggression made possible the ability to cooperate and communicate among foxes, dogs and bonobos.&lt;ref name=hareb2013/&gt;{{rp|114}}&lt;ref name=hare2005/&gt; The more docile animals have been found to have less testosterone than their more aggressive counterparts, and testosterone controls aggression and brain size.&lt;ref name=hood2014/&gt; The further away a dog breed is genetically from wolves, the larger the relative brain size is.&lt;ref&gt;[https://phys.org/news/2023-05-brains-modern-dog-larger-ancient.html Study finds the brains of modern dog breeds are larger than those of ancient breeds]&lt;/ref&gt;

=== Challenge ===

The domestication syndrome was reported to have appeared in the [[domesticated silver fox]] cultivated by [[Dmitry Belyayev (zoologist)|Dmitry Belyayev]]'s breeding experiment.&lt;ref name=Frantz2020/&gt; However, in 2015 canine researcher [[Raymond Coppinger]] found historical evidence that Belyayev's foxes originated in [[Fur farming|fox farms]] on [[Prince Edward Island]] and had been bred there for [[fur farming]] since the 1800s, and that the traits demonstrated by Belyayev had occurred in the foxes prior to the breeding experiment.&lt;ref&gt;{{Cite news |last=Gorman |first=James |date=2019-12-03 |title=Why Are These Foxes Tame? Maybe They Weren't So Wild to Begin With |work=[[The New York Times]] |url=https://www.nytimes.com/2019/12/03/science/foxes-tame-belyaev.html |access-date=2020-11-18}}&lt;/ref&gt; A 2019 opinion paper by Lord and colleagues argued that the results of the &quot;Russian farm fox experiment&quot; were overstated,&lt;ref name=&quot;Lord2019&quot; /&gt; although the pre-domesticated origins of these Russian foxes were already a matter of scientific record.&lt;ref name=&quot;:9&quot;&gt;{{Cite journal |last1=Statham |first1=Mark J. |last2=Trut |first2=Lyudmila N. |last3=Sacks |first3=Ben N. |last4=Kharlamova |first4=Anastasiya V. |last5=Oskina |first5=Irina N. |last6=Gulevich |first6=Rimma G. |last7=Johnson |first7=Jennifer L. |last8=Temnykh |first8=Svetlana V. |last9=Acland |first9=Gregory M. |last10=Kukekova |first10=Anna V. |date=May 2011 |title=On the origin of a domesticated species: identifying the parent population of Russian silver foxes (Vulpes vulpes): THE ORIGIN OF RUSSIAN SILVER FOXES |journal=Biological Journal of the Linnean Society |language=en |volume=103 |issue=1 |pages=168–175 |doi=10.1111/j.1095-8312.2011.01629.x |pmc=3101803 |pmid=21625363}}&lt;/ref&gt;

In 2020, Wright et al.&lt;ref&gt;{{Cite journal |last1=Wright |first1=Dominic |last2=Henriksen |first2=Rie |last3=Johnsson |first3=Martin |date=December 2020 |title=Defining the Domestication Syndrome: Comment on Lord et al. 2020 |url=https://linkinghub.elsevier.com/retrieve/pii/S016953472030224X |journal=Trends in Ecology &amp; Evolution |language=en |volume=35 |issue=12 |pages=1059–1060 |doi=10.1016/j.tree.2020.08.009|pmid=32917395 |bibcode=2020TEcoE..35.1059W |s2cid=221636622 |url-access=subscription }}&lt;/ref&gt; argued Lord et al.'s critique refuted only a narrow and unrealistic definition of domestication syndrome because their criteria assumed it must be caused by genetic pleiotropy, and arises in response to 'selection for tameness'--as was claimed by Belyaev,&lt;ref name=&quot;:7&quot;&gt;{{Cite journal |url=https://academic.oup.com/jhered/article/70/5/301/813519 |access-date=2024-03-05 |journal=Journal of Heredity|doi=10.1093/oxfordjournals.jhered.a109263 |title=Destabilizing selection as a factor in domestication |date=1979 |last1=Belyaev |first1=D. K. |volume=70 |issue=5 |pages=301–308 |pmid=528781 |url-access=subscription }}&lt;/ref&gt; Trut,&lt;ref name=&quot;:8&quot;&gt;{{Cite journal |last=Trut |first=Lyudmila |date=1999 |title=Early Canid Domestication: The Farm-Fox Experiment |url=http://www.americanscientist.org/issues/feature/1999/2/early-canid-domestication-the-farm-fox-experiment |journal=American Scientist |language=en |volume=87 |issue=2 |page=160 |doi=10.1511/1999.2.160 |issn=0003-0996 |archive-date=2017-04-01 |access-date=2024-03-05 |archive-url=https://web.archive.org/web/20170401042436/http://www.americanscientist.org/issues/feature/1999/2/early-canid-domestication-the-farm-fox-experiment |url-access=subscription }}&lt;/ref&gt; and the proposers of the neural crest hypothesis.&lt;ref name=&quot;:0&quot; /&gt;&lt;ref name=&quot;:6&quot; /&gt; In the same year, Zeder&lt;ref&gt;{{Cite journal |last=Zeder |first=Melinda A. |date=August 2020 |title=Straw Foxes: Domestication Syndrome Evaluation Comes Up Short |url=https://linkinghub.elsevier.com/retrieve/pii/S0169534720300756 |journal=Trends in Ecology &amp; Evolution |language=en |volume=35 |issue=8 |pages=647–649 |doi=10.1016/j.tree.2020.03.001|pmid=32668211 |bibcode=2020TEcoE..35..647Z |s2cid=216513400 |url-access=subscription }}&lt;/ref&gt; pointed out that it makes no sense to deny the existence of domestication syndrome on the basis that domestication syndrome traits were present in the pre-domesticated founding foxes.

The hypothesis that neural crest genes underlie some of the phenotypic differences between domestic and wild horses and dogs is supported by the functional enrichment of [[candidate genes]] under selection.&lt;ref name=Frantz2020/&gt; But, the observation of changed neural crest cell genes between wild and domestic populations need only reveal changes to features derived from neural crest, it does not support the claim of a common underlying genetic architecture that causes all of the domestication syndrome traits in all of the different animal species.&lt;ref name=&quot;:4&quot; /&gt;

Gleeson and Wilson&lt;ref name=&quot;:1&quot; /&gt; synthesised this debate and showed that animal domestication syndrome is not caused by selection for tameness, or by neural crest cell genetic pleiotropy. However, it could result from shared selective regime changes (which they termed 'reproductive disruption') leading to similarly shared trait changes across different species--in effect, a series of partial trait convergences. They proposed four primary selective pathways that are commonly altered by the shift to a domestic selective context, and would often lead to similar shifts in different populations. These pathways are: 

# Disrupted inter-sexual selection in males (reduced/altered female choice).
# Disrupted intra-sexual selection in males (reduced/altered male-male competition).
# Changed resource availability and predation pressure affecting female fertility and offspring survival.
# Intensified potential for maternal stress, selecting for altered reproductive physiology in females.&lt;ref name=&quot;:1&quot; /&gt;  
Because the 'Reproductive Disruption'&lt;ref name=&quot;:1&quot; /&gt; hypothesis explains domestication syndrome as a result of changed selective regimes, it can encompass multiple genetic or physiological ways that similar traits might emerge in the different domesticated species. For example, tamer behaviour might be caused by reduced adrenal reactivity,&lt;ref&gt;{{Cite journal |last1=Fallahsharoudi |first1=Amir |last2=de Kock |first2=Neil |last3=Johnsson |first3=Martin |last4=Ubhayasekera |first4=S. J. Kumari A. |last5=Bergquist |first5=Jonas |last6=Wright |first6=Dominic |last7=Jensen |first7=Per |date=2015-10-16 |title=Domestication Effects on Stress Induced Steroid Secretion and Adrenal Gene Expression in Chickens |journal=Scientific Reports |language=en |volume=5 |issue=1 |article-number=15345 |doi=10.1038/srep15345 |issn=2045-2322 |pmc=4608001 |pmid=26471470|bibcode=2015NatSR...515345F }}&lt;/ref&gt; by increased oxytocin production,&lt;ref&gt;{{Cite journal |last1=Herbeck |first1=Yu. E. |last2=Gulevich |first2=R. G. |last3=Shepeleva |first3=D. V. |last4=Grinevich |first4=V. V. |date=May 2017 |title=Oxytocin: Coevolution of human and domesticated animals |url=http://link.springer.com/10.1134/S2079059717030042 |journal=Russian Journal of Genetics: Applied Research |language=en |volume=7 |issue=3 |pages=235–242 |doi=10.1134/S2079059717030042 |s2cid=21631875 |issn=2079-0597|url-access=subscription }}&lt;/ref&gt; or by a combination of these or other mechanisms, across the different populations and species. 

== In plants ==

=== Syndrome traits ===

The same concept appears in the [[plant domestication]] process which produces [[crop]]s, but with its own set of syndrome traits. In cereals, these include little to no [[shattering (agriculture)|shattering]]&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;/fruit [[abscission]],&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt; shorter height (thus decreased [[lodging (agriculture)|lodging]]), larger [[grain]]&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt; or fruit&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt; size, easier [[threshing]], [[synchronous flowering]], altered timing of [[flowering]], increased grain weight,&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt; [[glutinous]]ness (stickiness, not [[gluten]] protein content),&lt;ref name=&quot;Lenser-Theissen-2013&quot;&gt;{{cite journal | last1=Lenser | first1=Teresa | last2=Theißen | first2=Günter | title=Molecular mechanisms involved in convergent crop domestication | journal=[[Trends in Plant Science]] | publisher=[[Cell Press]] | volume=18 | issue=12 | year=2013 | issn=1360-1385 | doi=10.1016/j.tplants.2013.08.007 | pages=704–714 | pmid=24035234| bibcode=2013TPS....18..704L }}&lt;/ref&gt;&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt; increased [[fruit]]/grain number, altered color compounds, taste, and texture, [[daylength]] independence, [[determinate growth]], lesser/no [[vernalization]], less [[seed dormancy]].&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt;

=== Cereal genes by trait ===

Control of the syndrome traits in cereals is by:&lt;!-- If you are adding a new gene, make sure you are not putting in a redundant species prefix (e.g. Os = Oryza sativa [rice], Ta = Triticum aestivum [wheat], Hv = Hordeum vulgare [barley])! --&gt;

; Shattering
* ''[[SH1 (gene)|SH1]]'' in [[sorghum]], rice, and [[maize|maize/corn]]&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;&lt;!-- &quot;qSH1&quot; is a duplicate, from when the gene was not yet identified from the [[qualitative trait locus]] --&gt;
* ''[[sh4 (gene)|sh4]]'' in the [[rachis]]&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt; of rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot;&gt;{{cite journal | last1=Chen | first1=Erwang | last2=Huang | first2=Xuehui | last3=Tian | first3=Zhixi | last4=Wing | first4=Rod A. | last5=Han | first5=Bin | title=The Genomics of ''Oryza'' Species Provides Insights into Rice Domestication and Heterosis | journal=[[Annual Review of Plant Biology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=70 | issue=1 | date=2019-04-29 | issn=1543-5008 | doi=10.1146/annurev-arplant-050718-100320 | pages=639–665| pmid=31035826 | bibcode=2019AnRPB..70..639C | s2cid=140266038 }}&lt;/ref&gt;
* ''[[qPDH1]]'' in [[soybean]]&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;
* ''[[Q (gene)|Q]]'' in wheat&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;
* ''[[LG1]]'' in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;

; Plant height
* ''[[Rht-B1]]''/''[[Rht-D1]]'' (two orthologous versions of ''Rht-1'' on different subgenomes, Rht standing for ''reduced height'') in wheat&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt;&lt;ref&gt;{{cite journal |last1=Pearce |first1=Stephen |last2=Saville |first2=Robert |last3=Vaughan |first3=Simon P. |last4=Chandler |first4=Peter M. |last5=Wilhelm |first5=Edward P. |last6=Sparks |first6=Caroline A. |last7=Al-Kaff |first7=Nadia |last8=Korolev |first8=Andrey |last9=Boulton |first9=Margaret I. |last10=Phillips |first10=Andrew L. |last11=Hedden |first11=Peter |last12=Nicholson |first12=Paul |last13=Thomas |first13=Stephen G. |title=Molecular Characterization of Rht-1 Dwarfing Genes in Hexaploid Wheat |journal=Plant Physiology |date=1 December 2011 |volume=157 |issue=4 |pages=1820–1831 |doi=10.1104/pp.111.183657 |pmid=22013218 |doi-access=free|pmc=3327217 }}&lt;/ref&gt;
* ''[[GA20ox-2]]'' in rice and barley&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt;
* ''[[KO2]]'' in one Japanese cultivar of rice&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt;
* either ''[[dw3]]'' or ''[[d2 (gene)|d2]]'' in sorghum and [[pearl millet]]&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;
* ''[[Ghd7]]'' in rice&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt;
* ''[[Q (gene)|Q]]'' in wheat&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt;

;Grain size
* ''[[GS3 (gene)|GS3]]'' in maize/corn and rice&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;
* ''[[GS5 (gene)|GS5]]'' in rice&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;
* ''[[An-1 (gene)|An-1]]'' in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;
* ''[[GAD1]]/RAE2'' (smaller) in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;

; Yield
* [[Oryza sativa SPL14|SPL14]]/LOC4345998 in rice.&lt;ref name=&quot;Stange-et-al-2021&quot;&gt;{{cite journal |last1=Stange |first1=Madlen |last2=Barrett |first2=Rowan D. H. |last3=Hendry |first3=Andrew P. |title=The importance of genomic variation for biodiversity, ecosystems and people |journal=[[Nature Reviews Genetics]] |publisher=[[Nature Portfolio]] |volume=22 |issue=2 |date=February 2021 |issn=1471-0056 |doi=10.1038/s41576-020-00288-7 |pages=89–105 |pmid=33067582 |s2cid=223559538}}&lt;/ref&gt;
* ''[[pyl1]]'', ''[[pyl4]]'', ''[[pyl6]]'' in the ''[[PYR1-like|PYL]]'' gene family in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Threshability
* ''[[Q (gene)|Q]]''&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt; and ''[[Nud (gene)|Nud]]''&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;
* ''[[An-1 (gene)|An-1]]'' (by reducing or eliminating [[awn (botany)|awn]]s) in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;
* ''[[An-2 (gene)|An-2]]/[[LABA1]]'' - small awn reduction/barbless awns&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt; - in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;
* ''[[GAD1]]/RAE2'' - awn elimination in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;
* ''[[tga1]]'' - naked kernels in maize&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Flowering time
* ''[[VRN1]]'' in [[barley]], wheat, [[ryegrass]]&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;

; Grain weight
* ''[[GW2 (gene)|GW2]]'' in rice,&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt; wheat,&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt; maize/corn&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;
* ''[[GW5]]'' in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;
* ''[[GLW2]]'' in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;
* ''[[GASR7]]'' in wheat&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;
* ''[[GW5]]'' in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;
* ''[[TGW6]]'' in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Glutinousness
&lt;!-- I, II... these are roman numerals. --&gt;
* ''[[GBSSI]]'' or ''[[Waxy (gene)|Waxy]]'' in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot;&gt;{{cite journal | last1=Chen | first1=Kunling | last2=Wang | first2=Yanpeng | last3=Zhang | first3=Rui | last4=Zhang | first4=Huawei | last5=Gao | first5=Caixia | title=CRISPR/Cas Genome Editing and Precision Plant Breeding in Agriculture | journal=Annual Review of Plant Biology | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=70 | issue=1 | date=2019-04-29 | issn=1543-5008 | doi=10.1146/annurev-arplant-050718-100049 | pages=667–697| pmid=30835493 | s2cid=73471425 | doi-access=free | bibcode=2019AnRPB..70..667C }}&lt;/ref&gt; (especially [[glutinous rice]]), wheat, corn, barley, sorghum,&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt; [[foxtail millet]]&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;&lt;ref name=&quot;Purugganan-Fuller-2009&quot;&gt;{{cite journal | last1=Purugganan | first1=Michael D. | last2=Fuller | first2=Dorian Q. | title=The nature of selection during plant domestication | journal=[[Nature (journal)|Nature]] | publisher=[[Nature Research]] | volume=457 | issue=7231 | year=2009 | issn=0028-0836 | doi=10.1038/nature07895 | pages=843–848| pmid=19212403 | bibcode=2009Natur.457..843P | s2cid=205216444 }}&lt;/ref&gt;
* ''[[SBEIIb]]'' in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;

; Determinate growth
* ''[[TERMINAL FLOWER 1]]/[[TFL1]]'' in ''[[Arabidopsis thaliana]]'' and orthologs&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt;
** Specifically, four orthologs in ''[[Glycine max]]'' and eight in ''[[Phaseolus vulgaris]]''&lt;ref name=&quot;Lenser-Theissen-2013&quot; /&gt;

; Standability
* ''[[PROSTRATE GROWTH]]/[[Prog1 (growth gene)|Prog1]]/[[PROG1]]'' in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;
* ''[[teosinte branched1]]/[[tb1 (gene)|tb1]]'' ([[apical dominance]]) in maize/corn&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;

; Grain/fruit number
* ''[[An-1 (gene)|An-1]]'' in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;
* ''[[GAD1]]/RAE2'' in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;
* ''[[PROG1 (tiller gene)|PROG1]]'' (by increasing tiller number) in rice&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;
* ''[[Gn1a]]'' in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;
* ''[[AAP3]]'' (by increasing tiller number) in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Panicle size
* ''[[DEP1]]'' in rice and wheat&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Spike number
* ''[[vrs1]]'' in barley&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Fragrance
* ''[[BADH2]]'' produces [[2-Acetyl-1-pyrroline]] when defective in rice;&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt; can be [[transcription activator-like effector nuclease|artificially disrupted]] to produce the same compound&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Delayed sprouting
* ''[[pyl1]]'', ''[[pyl4]]'', ''[[pyl6]]'' in the ''[[PYR1-like|PYL]]'' gene family - reduced preharvest [[sprouting]] in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Altered color

* ''[[Rc (gene)|Rc]]'' - white [[pericarp]] in rice&lt;ref name=&quot;Chen-Wang-et-al-2019&quot; /&gt;

; Unspecified trait
* ''[[Teosinte glume architecture]]/[[tga (gene)|tga]]'' in maize/corn&lt;ref name=&quot;Chen-Huang-et-al-2019&quot; /&gt;

Many of these are mutations in [[regulatory gene]]s, especially [[transcription factor]]s, which is likely why they work so well in domestication: They are not new, and are relatively ready to have their magnitudes altered. In annual grains, [[loss of function]] and [[altered expression]] are by far the most common, and thus are the most interesting goals of [[mutation breeding]], while [[copy number variation]] and [[chromosomal rearrangement]]s are far less common.&lt;ref name=&quot;Kantar-et-al-2016&quot; /&gt;

== See also ==
* [[Agricultural weed syndrome]]

==References==
{{Reflist|refs=

&lt;ref name=hare2005&gt;{{cite journal|author=Hare, Brian|author-link=Brian Hare|year=2005|title=Human-like social skills in dogs?|journal=Trends in Cognitive Sciences|volume=9|issue=9|pages=439–44|pmid=16061417|doi=10.1016/j.tics.2005.07.003|s2cid=9311402}}&lt;/ref&gt;

&lt;ref name=hareb2013&gt;{{cite book|author=Hare, Brian|author-link=Brian Hare|year=2013|title=The Genius of Dogs|publisher=Penguin Publishing Group}}&lt;/ref&gt;

&lt;!--
&lt;ref name=hare2017&gt;{{cite journal|doi=10.1146/annurev-psych-010416-044201|title=Survival of the Friendliest:Homo sapiens ''Evolved'' via Selection for Prosociality|year=2017|last1=Hare|first1=Brian|author-link=Brian Hare|journal=Annual Review of Psychology|volume=68|pages=155–186|pmid=27732802|s2cid=3387266}}&lt;/ref&gt;
--&gt;

&lt;ref name=hood2014&gt;{{cite book|author=[[Bruce Hood (psychologist)]]|year=2014|title=The Domesticated Brain|publisher=Pelican|isbn=978-0-14-197486-6}}Preface&lt;/ref&gt;

&lt;ref name=Frantz2020&gt;{{cite journal|doi=10.1038/s41576-020-0225-0|title=Animal domestication in the era of ancient genomics|year=2020|last1=Frantz|first1=Laurent A. F.|last2=Bradley|first2=Daniel G.|last3=Larson|first3=Greger|last4=Orlando|first4=Ludovic|journal=Nature Reviews Genetics|volume=21|issue=8|pages=449–460|pmid=32265525|s2cid=214809393|url=https://qmro.qmul.ac.uk/xmlui/handle/123456789/66726}}&lt;/ref&gt;

&lt;!--
&lt;ref name=Irving-Pease2018&gt;{{cite book|doi=10.1007/13836_2018_55|chapter=Paleogenomics of Animal Domestication|title=Paleogenomics|pages=225–272|series=Population Genomics|year=2018|last1=Irving-Pease|first1=Evan K.|last2=Ryan|first2=Hannah|last3=Jamieson|first3=Alexandra|last4=Dimopoulos|first4=Evangelos A.|last5=Larson|first5=Greger|last6=Frantz|first6=Laurent A. F.|publisher=Springer, Cham|editor1-last=Lindqvist|editor1-first=C.|editor2-last=Rajora|editor2-first=O.|isbn=978-3-030-04752-8|chapter-url=http://qmro.qmul.ac.uk/xmlui/handle/123456789/46323}}&lt;/ref&gt;
--&gt;

&lt;ref name=Lord2019&gt;{{cite journal|last1=Lord|first1=Kathryn A.|last2=Larson|first2=Greger|last3=Coppinger|first3=Raymond P.|last4=Karlsson|first4=Elinor K.|year=2020|title=The History of Farm Foxes Undermines the Animal Domestication Syndrome|journal=Trends in Ecology &amp; Evolution|volume=35|issue=2|pages=125–136|doi=10.1016/j.tree.2019.10.011|pmid=31810775|doi-access=free|bibcode=2020TEcoE..35..125L }}&lt;/ref&gt;

&lt;ref name=machugh2016&gt;{{cite journal|doi=10.1146/annurev-animal-022516-022747|pmid=27813680|title=Taming the Past: Ancient DNA and the Study of Animal Domestication|journal=Annual Review of Animal Biosciences|volume=5|pages=329–351|year=2016|last1=Machugh|first1=David E.|last2=Larson|first2=Greger|last3=Orlando|first3=Ludovic}}&lt;/ref&gt;

&lt;!--
&lt;ref name=pendleton2018&gt;{{cite journal|doi=10.1186/s12915-018-0535-2|pmid=29950181|pmc=6022502|title=Comparison of village dog and wolf genomes highlights the role of the neural crest in dog domestication|journal=BMC Biology|volume=16|issue=1|page=64|year=2018|last1=Pendleton|first1=Amanda L.|last2=Shen|first2=Feichen|last3=Taravella|first3=Angela M.|last4=Emery|first4=Sarah|last5=Veeramah|first5=Krishna R.|last6=Boyko|first6=Adam R.|last7=Kidd|first7=Jeffrey M. |doi-access=free }}&lt;/ref&gt;
--&gt;
}}

{{Animal domestication}}

[[Category:Agriculture]]
[[Category:Domestication]]
[[Category:Genetics]]
[[Category:Syndromes in animals]]
[[Category:Syndromes in birds]]
[[Category:Syndromes in cats]]
[[Category:Syndromes in crustaceans]]
[[Category:Syndromes in dogs]]
[[Category:Syndromes in fish]]
[[Category:Syndromes in horses]]
[[Category:Syndromes in mammals]]
[[Category:Syndromes in plants]]