Cranial Allometry and the Evolution of the Domestic Dog

Domestication is usually defined as a process involving human subjugation of other animal or plant species. From this perspective, it is often presumed that morphological changes in domestic animals are the product of conscious or unconscious human selection. A broader evolutionary perspective does not make this presumption. The origin of the domestic dog (Canis familiaris) is best understood as a consequence of human adoption of wolf pups (Canis lupus) some 12,000 years ago. Young wolf pups growing up in human society formed their primary social bonds with humans. The radically altered circumstances experienced by these early domestic canids placed them in a new role as ecological colonizers. Selection under these circumstances favored precocious maturation, resulting in evolutionary progenesis, a form of heterochrony. Concurrently, an abrupt shift in diet resulted in rapid size reduction in the new evolving species. Craniometric data analyzed from modern wild Canis and prehistoric domesticated dogs from North America and northern Europe, all predating 3,000 B.P. The goal is to assess whether or not morphological changes in dogs are allometric consequences of size reduction, brought about by heterochronic alterations. Previous investigations of canid allometry involving wild canids and modern dog breeds serve as a frame of reference. Bivariate analysis of static data reveals that the dogs exhibit uniquely wide cranial vaults and palates, and are distinct from allometric trends seen among other groups. Anterior cranial length variables are tightly scaled among all groups, with proportional variation a consequence of allometric scaling. Dogs also tend to have proportionally longer teeth than similar sized wild canids. Bivariate analysis of ontogenetic data reveals that wide vaults and palates in dogs are associated with a greater correspondence to wolf ontogenetic regression lines relative to other groups. On anterior cranial length variables all groups exhibit evidence of ontogenetic scaling. Multivariate analysis indicates that dogs are morphologically more similar to juvenile wolves than to any adult group. Juvenilized morphology in dogs is a consequence of rapid size change with morphology constrained to developmental pathways. Invariance in gestation period in Canis may pose a fundamental morphological constraint on dog morphology. Confinement of morphology to developmental boundaries may be indicative of rapid evolutionary change in general. Heterochronic mechanisms responsible for this mode of change may be important in the evolution of domestic animals other and the dog

Paleoeskimo Dogs of the Eastern Arctic

Sled or pack dogs have been perceived as an integral part of traditional life in the Eastern Arctic. This perception stems from our knowledge of the lifeway of recent Thule and modern Inuit peoples, among whom dog sledding has often been an important means of transportation. In contrast, the archaeological record of preceding Paleoeskimo peoples indicates that dogs were sparse at most, and probably locally absent for substantial periods. This pattern is real, not an artifact of taphonomic biases or difficulties in distinguishing dog from wolf remains. Analysis of securely documented dog remains from Paleoeskimo sites in Greenland and Canada underscores the sporadic presence of only small numbers of dogs, at least some of which were eaten. This pattern should be expected. Dogs did not, and could not, assume a conspicuous role in North American Arctic human ecology outside the context of several key features of technology and subsistence production associated with Thule peoples.On a toujours considéré les chiens de traîneau ou chiens de somme comme faisant partie intégrante de la vie traditionnelle dans l'Arctique oriental. Cette perception vient de nos connaissances sur le mode de vie des derniers Thulés et des Inuits modernes, chez qui le traîneau à chiens a souvent représenté un mode de transport majeur. En revanche, les données archéologiques des peuples paléoesquimaux qui ont précédé Thulés et Inuits révèlent que les chiens étaient tout au plus clairsemés, et probablement absents localement pendant de longues périodes. Cette répartition est bien réelle et n'est pas le produit de distorsions taphonomiques ou de difficultés à faire la distinction entre les restes du chien et ceux du loup. L'analyse de restes canins proprement documentés trouvés sur des sites paléoesquimaux au Groenland et au Canada souligne la présence sporadique de chiens en nombre toujours restreint, dont au moins quelques-uns étaient mangés. Cette répartition n'est pas surprenante, les chiens n'assumant pas - et ne pouvant assumer - un rôle évident dans l'écologie humaine de l'Arctique nord-américain en dehors du contexte de diverses caractéristiques clés de la technologie et de la production de subsistance associées aux Thulés

The FANCM:p.Arg658* truncating variant is associated with risk of triple-negative breast cancer

Abstract: Breast cancer is a common disease partially caused by genetic risk factors. Germline pathogenic variants in DNA repair genes BRCA1, BRCA2, PALB2, ATM, and CHEK2 are associated with breast cancer risk. FANCM, which encodes for a DNA translocase, has been proposed as a breast cancer predisposition gene, with greater effects for the ER-negative and triple-negative breast cancer (TNBC) subtypes. We tested the three recurrent protein-truncating variants FANCM:p.Arg658*, p.Gln1701*, and p.Arg1931* for association with breast cancer risk in 67,112 cases, 53,766 controls, and 26,662 carriers of pathogenic variants of BRCA1 or BRCA2. These three variants were also studied functionally by measuring survival and chromosome fragility in FANCM−/− patient-derived immortalized fibroblasts treated with diepoxybutane or olaparib. We observed that FANCM:p.Arg658* was associated with increased risk of ER-negative disease and TNBC (OR = 2.44, P = 0.034 and OR = 3.79; P = 0.009, respectively). In a country-restricted analysis, we confirmed the associations detected for FANCM:p.Arg658* and found that also FANCM:p.Arg1931* was associated with ER-negative breast cancer risk (OR = 1.96; P = 0.006). The functional results indicated that all three variants were deleterious affecting cell survival and chromosome stability with FANCM:p.Arg658* causing more severe phenotypes. In conclusion, we confirmed that the two rare FANCM deleterious variants p.Arg658* and p.Arg1931* are risk factors for ER-negative and TNBC subtypes. Overall our data suggest that the effect of truncating variants on breast cancer risk may depend on their position in the gene. Cell sensitivity to olaparib exposure, identifies a possible therapeutic option to treat FANCM-associated tumors

Size, shape and development in the evolution of the domestic dog

An explanation for the ubiquitous morphological changes during the evolutionary divergence of the domestic dog (Canis familiaris) from the wolf (Canis lupus) has proven elusive. These changes include size reduction, facial shortening and tooth crowding. The ubiquity of these changes suggests that they are unlikely to be direct products of human selection. In this paper explanation of morphological change is approached through allometric analysis of craniometric data from prehistoric domestic dogs from North America and northern Europe and from recent wild Canis. Results indicate that anterior cranial length dimensions are tightly scaled among all Canis, while the dogs show divergent allometries on cranial width dimensions. These patterns are consistent with previous allometric studies involving modern dog breeds. Morphological patterning in dogs is not reasonably explained solely as a by-product of biomechanical constraints associated with size reduction. Rather, morphology is constrained by developmental boundaries, reflecting heterochronic alterations produced by strong selection for size reduction and modified reproductive strategy. Unique dental allometries of dogs stem from lack of tight developmental integration between dental growth and overall somatic growth. Further analysis should focus on the relationship between ancestral ontogeny and adult morphology in dogs

Size, shape and development in the evolution of the domestic dog

An explanation for the ubiquitous morphological changes during the evolutionary divergence of the domestic dog (Canis familiaris) from the wolf (Canis lupus) has proven elusive. These changes include size reduction, facial shortening and tooth crowding. The ubiquity of these changes suggests that they are unlikely to be direct products of human selection. In this paper explanation of morphological change is approached through allometric analysis of craniometric data from prehistoric domestic dogs from North America and northern Europe and from recent wild Canis. Results indicate that anterior cranial length dimensions are tightly scaled among all Canis, while the dogs show divergent allometries on cranial width dimensions. These patterns are consistent with previous allometric studies involving modern dog breeds. Morphological patterning in dogs is not reasonably explained solely as a by-product of biomechanical constraints associated with size reduction. Rather, morphology is constrained by developmental boundaries, reflecting heterochronic alterations produced by strong selection for size reduction and modified reproductive strategy. Unique dental allometries of dogs stem from lack of tight developmental integration between dental growth and overall somatic growth. Further analysis should focus on the relationship between ancestral ontogeny and adult morphology in dogs