The Russian Farm-Fox Experiment is the best known experimental study in animal domestication. By subjecting a population of foxes to selection for tameness alone, Dimitry Belyaev generated foxes that possessed a suite of characteristics that mimicked those found across domesticated species. This 'domestication syndrome' has been a central focus of research into the biological pathways modified during domestication. Here, we chart the origins of Belyaev's foxes in eastern Canada and critically assess the appearance of domestication syndrome traits across animal domesticates. Our results suggest that both the conclusions of the Farm-Fox Experiment and the ubiquity of domestication syndrome have been overstated. To understand the process of domestication requires a more comprehensive approach focused on essential adaptations to human-modified environments. The Origins of Domestication SyndromeThe domestication syndrome describes a suite of behavioral and morphological characteristics consistently observed in domesticated populations. It was first described in animals (although not named as such) by Charles Darwin [1]. The term itself, coined by botanists in the early 1900s [2,3], was applied to animals in the 1980s [3]. Usage has risen dramatically since the mid-1990s, by more than 20-fold (see the supplemental information online) [4].The concept of a domestication syndrome is appealing. The grouping of a collection of traits allows easier identification and facilitates the definition of domesticated taxa. It also inspires a search for causal mechanisms, whether genetic or environmental, responsible for their collective appearance. Characteristics attributed to domestication syndrome vary, but include tamability (see Glossary), loss of reproductive seasonality, and changes in coat color, ear form, tail form, and craniofacial morphology (Figure 1) [1,[5][6][7][8][9][10][11][12][13].

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Behavioral genetics in dogs has focused on modern breeds, which are isolated subgroups with distinctive physical and, purportedly, behavioral characteristics. We interrogated breed stereotypes by surveying owners of 18,385 purebred and mixed-breed dogs and genotyping 2155 dogs. Most behavioral traits are heritable [heritability ( h 2 ) > 25%], and admixture patterns in mixed-breed dogs reveal breed propensities. Breed explains just 9% of behavioral variation in individuals. Genome-wide association analyses identify 11 loci that are significantly associated with behavior, and characteristic breed behaviors exhibit genetic complexity. Behavioral loci are not unusually differentiated in breeds, but breed propensities align, albeit weakly, with ancestral function. We propose that behaviors perceived as characteristic of modern breeds derive from thousands of years of polygenic adaptation that predates breed formation, with modern breeds distinguished primarily by aesthetic traits.