title: Establishing the validity of domestication genes using DNA from ancient chickens.
abstract: Modern domestic plants and animals are subject to human-driven selection for desired phenotypic traits and behavior. Large-scale genetic studies of modern domestic populations and their wild relatives have revealed not only the genetic mechanisms underlying specific phenotypic traits, but also allowed for the identification of candidate domestication genes. Our understanding of the importance of these genes during the initial stages of the domestication process traditionally rests on the assumption that robust inferences about the past can be made on the basis of modern genetic datasets. A growing body of evidence from ancient DNA studies, however, has revealed that ancient and even historic populations often bear little resemblance to their modern counterparts. Here, we test the temporal context of selection on specific genetic loci known to differentiate modern domestic chickens from their extant wild ancestors. We extracted DNA from 80 ancient chickens excavated from 12 European archaeological sites, dated from ∼ 280 B.C. to the 18th century A.D. We targeted three unlinked genetic loci: the mitochondrial control region, a gene associated with yellow skin color (β-carotene dioxygenase 2), and a putative domestication gene thought to be linked to photoperiod and reproduction (thyroid-stimulating hormone receptor, TSHR). Our results reveal significant variability in both nuclear genes, suggesting that the commonality of yellow skin in Western breeds and the near fixation of TSHR in all modern chickens took place only in the past 500 y. In addition, mitochondrial variation has increased as a result of recent admixture with exotic breeds. We conclude by emphasizing the perils of inferring the past from modern genetic data alone.
authors.affiliation: Durham Evolution and Ancient DNA, Department of Archaeology, School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom.
authors.forename: Linus
authors.initials: L
authors.lastname: Girdland Flink
authors.forename: Richard
authors.initials: R
authors.lastname: Allen
authors.forename: Ross
authors.initials: R
authors.lastname: Barnett
authors.forename: Helena
authors.initials: H
authors.lastname: Malmström
authors.forename: Joris
authors.initials: J
authors.lastname: Peters
authors.forename: Jonas
authors.initials: J
authors.lastname: Eriksson
authors.forename: Leif
authors.initials: L
authors.lastname: Andersson
authors.forename: Keith
authors.initials: K
authors.lastname: Dobney
authors.forename: Greger
authors.initials: G
authors.lastname: Larson
mesh_terms: D000818:Animals; D000829:Animals, Domestic / Q000235:genetics*; D002645:Chickens / Q000235:genetics*; D004247:DNA / Q000235:genetics* / Q000266:history*; D004272:DNA, Mitochondrial / Q000235:genetics; D005060:Europe; D005843:Geography; D006239:Haplotypes / Q000235:genetics; D049690:History, Ancient; D006801:Humans; D008969:Molecular Sequence Data; D015203:Reproducibility of Results
chemical_list: D004272:DNA, Mitochondrial; D004247:DNA
keywords: Gallus gallus; animal domestication; breed formation; cultural history; selective sweep
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