By Ophélie Lebrasseur, Associate Editor for Archaeogenetics
(Ophélie actually sent two photos to go with this post, but in one photo the chickens were staring right at Carmen, who has a deep phobia of chickens or animals with beaks. So, she had to give that one up...sorry!)
Our favourite domestic bird is once again in the spotlight, with a major study shedding light on the much-debated topic of its domestication.
Domestic chickens are found ubiquitously across regions and cultures, with nearly three individuals for every human being. Yet for such a popular bird, we know surprisingly little about its domestication. Our general understanding is that chickens were domesticated in South/ Asia from the Red Jungle fowl (RJF, Gallus gallus), though the Grey Jungle Fowl (Gallus sonneratii) also contributed to their genetic make-up, notably giving them their yellow skin and legs (a trait absent in RJFs) (Eriksson et al., 2008). The timing of their domestication, however, has long been debated, with an initial suggested date of 8000 years BP (West & Zhou, 1988), later reviewed to the ~2nd millennium BP (Eda et al., 2019; Peters et al., 2016; Huang et al., 2018).
Now, Wang and his team (2020) have delved deeper into the origin story of this domestic bird armed with 863 whole genomes from modern domestic chickens and representatives of the four Jungle Fowl species (Gallus gallus, Gallus sonneratii, Gallus varius and Gallus lafayettii) including all five RJF subspecies G. g. gallus, G. g. spadiceus, G. g. jabouillei, G. g. murghi and G. g. bankiva. Such high genetic resolution confirmed chickens were domesticated from the RJF but have refined this origin specifically to G. g. spadiceus, a RJF subspecies currently indigenous to Southwestern China, Thailand and Myanmar. Molecular clock analyses place the divergence between this subspecies and their domestic descendants around 9500 +/- 3300 years BP, but this date doesn’t necessarily reflect the beginning of the domestication process as archaeological evidence points to a much later date. This is similar to what is observed in modern wolves and dogs, with a divergence time estimated based on molecular data to occur ~15,000 years prior to the evidence found in the archaeological record (Wang et al., 2016; Frantz et al., 2016). Following their domestication, chickens then spread across Southeast and South Asia, interbreeding not only with other local yet highly divergent RJF subspecies, but also other Jungle Fowl species. Wang et al. also identified multiple genes involved in behaviours, growth and reproduction, and found that the loci TSHR_Gly558Arg may not have played as important a role in domestication as what was originally believed. The loci is fixed in both domestic chicken populations and G. g. spadiceus, contrary to other RJF subspecies where it remains in low frequencies. Such mutation must thus have occurred in G. g. spadiceus populations prior to domestication, and have been present at high frequencies in the original domestic chicken flocks. This frequency may have been reduced following admixture events with other RJF subspecies until selection increased it again to the frequency we see today. These findings represent a major step towards understanding the domestication of the most popular bird on the planet.
For access to the full article: Wang, M., Thakur, M., Peng, M. et al. (2020) 863 genomes reveal the origin and domestication of chicken. Cell Research. https://doi.org/10.1038/s41422-020-0349-y
Are you conducting research on chickens? Then you may be interested in joining the ‘Chicken Journal Club’. Dessislava Veltcheva and Sophie Hedges invite you to join a new journal club joining researchers in the fields of (but not limited to) chickens from the gut microbiome, experimental chickens, antibiotic usage and resistance, mathematical models, domestication of chickens, immunity, etc.
If you are interested please sign up here[ https://forms.gle/MYtFhavqi1BqBxwQ6.] and please send an email to Dessy (dessislava.veltcheva@spc.ox.ac.uk) or Sophie (shedges@rvc.ac.uk). Thank you!
References
Eda, M., Kikuchi, H., Sun, G. and Matsui, A. (2019) Were chickens exploited in the Neolithic early rice cultivation society of the lower Yangtze River? Archaeological and Anthropological Sciences, 11(12):6423-6430.
Eriksson, J., Larson, G., Gunnarsson, U., Bed'hom, B., Tixier-Boichard, M., Strömstedt, L., et al. (2008) Identification of the Yellow Skin Gene Reveals a Hybrid Origin of the Domestic Chicken. PLoS Genet 4(2):e1000010. https://doi.org/10.1371/journal.pgen.1000010
Frantz, L., Mullin, V., Pionnier-Capitan, M., Lebrasseur, O. et al. (2016) Genomic and archaeological evidence suggest a dual origin of domestic dogs. Science 352(6290):1128-1231
Huang, X-H., Wu, Y-J., Miao, Y-W., et al. (2018) Was chicken domesticated in northern China? New evidence from mitochondrial genomes. Science Bulletin 63(12):743-746.
Peters, J., Lebrasseur, O., Deng, H. and Larson, G. (2016) Holocene cultural history of Red Jungle Fowl (Gallus gallus) and its domestic descendant in East Asia. Quat. Sci. Rev. 142:102-119.
Wang, G., Zhai, W., Yang, H. et al. (2016) Out of southern East Asia: the natural history of domestic dogs across the world. Cell Res 26, 21–33. https://doi.org/10.1038/cr.2015.147
West, B. and Zhou, B-X. (1988) Did chickens go North? New evidence for domestication. J. Arch. Sci. 15(15):515-533.
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