title: Facial shape differences between rats selected for tame and aggressive behaviors.
abstract: Domestication has been consistently accompanied by a suite of traits called the domestication syndrome. These include increased docility, changes in coat coloration, prolonged juvenile behaviors, modified function of adrenal glands and reduced craniofacial dimensions. Wilkins et al recently proposed that the mechanistic factor underlying traits that encompass the domestication syndrome was altered neural crest cell (NCC) development. NCC form the precursors to a large number of tissue types including pigment cells, adrenal glands, teeth and the bones of the face. The hypothesis that deficits in NCC development can account for the domestication syndrome was partly based on the outcomes of Dmitri Belyaev's domestication experiments initially conducted on silver foxes. After generations of selecting for tameness, the foxes displayed phenotypes observed in domesticated species. Belyaev also had a colony of rats selected over 64 generations for either tameness or defensive aggression towards humans. Here we focus on the facial morphology of Belyaev's tame, 'domesticated' rats to test whether: 1) tameness in rats causes craniofacial changes similar to those observed in the foxes; 2) facial shape, i.e. NCC-derived region, is distinct in the tame and aggressive rats. We used computed-tomography scans of rat skulls and landmark-based geometric morphometrics to quantify and analyze the facial skeleton. We found facial shape differences between the tame and aggressive rats that were independent of size and which mirrored changes seen in domesticated animals compared to their wild counterparts. However, there was no evidence of reduced sexual dimorphism in the face of the tame rats. This indicates that not all morphological changes in NCC-derived regions in the rats follow the pattern of shape change reported in domesticated animals or the silver foxes. Thus, certain phenotypic trends that are part of the domestication syndrome might not be consistently present in all experimental animal models.
authors.affiliation: Paleoanthropology, Senckenberg Center for Human Evolution & Paleoenvironment, Eberhard Karls Universität Tübingen, Tübingen, Germany.|Department of Anthropology, Pennsylvania State University, University Park, United States of America.
authors.forename: Nandini
authors.identifier: http://orcid.org/0000-0001-9019-4707
authors.initials: N
authors.lastname: Singh
authors.affiliation: Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.|Department of Genetics, Cell Biology, and Development, College of Biological Sciences, University of Minnesota, Minneapolis, United States of America.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Albert
authors.affiliation: Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.
authors.forename: Irina
authors.initials: I
authors.lastname: Plyusnina
authors.affiliation: Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.
authors.forename: Lyudmila
authors.initials: L
authors.lastname: Trut
authors.affiliation: Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
authors.forename: Svante
authors.initials: S
authors.lastname: Pӓӓbo
authors.affiliation: Paleoanthropology, Senckenberg Center for Human Evolution & Paleoenvironment, Eberhard Karls Universität Tübingen, Tübingen, Germany.|DFG Centre for Advanced Studies: Words, Bones, Genes, Tools: Tracking linguistic, cultural and biological trajectories of the human past, Eberhard Karls Universität Tübingen, Tübingen, Germany.
authors.forename: Katerina
authors.initials: K
authors.lastname: Harvati
mesh_terms: D000374:Aggression / Q000502:physiology*; D000818:Animals; D000829:Animals, Domestic / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D001947:Breeding; D000071278:Domestication; D005145:Face / Q000502:physiology*; D005149:Facial Expression; D005589:Foxes / Q000502:physiology; D051381:Rats; D012886:Skull / Q000502:physiology