Background/Objectives: The well-established inverse relationship between lifespan and weight across dog breeds has been associated with higher cancer mortality in larger breeds. However, Peto’s paradox implies that larger-bodied species experience lower-than-expected rates of cancer mortality because of higher levels of cancer suppression. Therefore, it has been hypothesised that recently established large dog breeds experience high cancer mortality because of a lag in their evolution of cancer suppression. This “adaptive lag hypothesis” predicts that ancient breeds, which have had more time to evolve optimal cancer suppression, exhibit lower cancer mortality rates, longer lifespans, and smaller litter sizes (a cost of cancer suppression) compared to modern breeds of the same size. Methods: The adaptive lag hypothesis is tested here by comparing ancient and modern breeds defined by their levels of modern European genetic admixture. Results: Ancient breeds have significantly longer lifespans and smaller litters than modern breeds of the same size after controlling for phylogenetic relationships. The sparse data on cancer mortality rates of ancient breeds do not allow a definitive test of a difference between ancient and modern breeds, but ancient breeds show a significant departure from the increase in cancer mortality rate with weight observed for modern breeds. Conclusions: The results are consistent with the adaptive lag hypothesis, that the evolution of cancer suppression in large modern dog breeds has lagged behind their increased risk of cancer, thus shortening their lives compared to smaller breeds and compared to ancient breeds of the same size.

Heartworms (Dirofilaria immitis) are parasitic nematodes that cause significant cardiopulmonary-associated morbidity and mortality in canids worldwide. The global spread of heartworms is believed to have occurred alongside the dispersal of modern domesticated dogs over the past few hundred years. However, this conclusion has been based on limited sampling, both geographically and numerically. To test this theory more rigorously, we analyse the whole genomes of 127 adult heartworm specimens collected from mammalian carnivore hosts across Australia, the USA, Central America, Europe, and Asia. Here we show distinct genetic differences between heartworms from different continents, indicating a more ancient dispersal in canid hosts than previously recognised. Using genetic diversity and admixture analyses, we find an Asian origin for Australian heartworms, aligning with the arrival of dingoes into Australia via Asia thousands of years ago; however, we cannot exclude the alternate hypothesis that heartworms were also introduced from Asia in post-colonial times. Finally, the genetic relatedness between European and Central American heartworms suggests that modern dispersal, potentially associated with human colonisation of the Americas by Europeans, occurred with domesticated dogs. This work sheds light on the population dynamics and deep evolutionary history of a globally widespread parasite of veterinary significance.

The relationship between δ18O values in phosphate (δ18OP) and carbonate (δ18OC) fractions of dental enamel bioapatite is a tool for evaluating the preservation of isotopic signals in fossil teeth. Until now, this relationship has been recognised mainly in ungulates. To expand the database to a statistically representative set of carnivorans, δ18OP and δ18OC values were analysed in 32 samples from modern dogs and foxes collected in Poland. The results obtained for canids are consistent with data reported for other mammals, suggesting a universal model of oxygen isotope fractionation between enamel phosphate and carbonate in mammals, including carnivorans, artiodactyls, and perissodactyls.

Dogs evolved through interactions between people and gray wolves during the Late Pleistocene and have been ubiquitous in human societies ever since. Instances of wolf-to-dog introgression are rare, but adaptive introgression has been shown in association with high-altitude survival. Any widespread gene flow, however, has fallen below thresholds of detection in genome-wide statistical assessments. To reexamine evidence of dog-wolf gene flow, we analyzed 2,693 published dog and wolf genomes and combined highly sensitive local ancestry inference and phylogenomic analyses of nuclear genes, mitochondrial genomes, and Y-chromosome sequences. Although dogs and wolves segregate decisively at the nuclear level, no individual nuclear gene tree supports dog monophyly. Uniparental markers show mixed and interleaved dog and wolf clades with strong support and incongruent phylogenetic topologies. Using local ancestry inference, we find that 64.1% of modern breed dogs carry wolf ancestry from admixture that occurred nearly a thousand generations ago on average and now covers ~0.14% of their individual nuclear genomes. Among modern free-living village dogs (n = 280), 100% of analyzed genomes carry wolf ancestry. We find that wolf ancestry in dog breeds correlates with functional traits including size, breed category, and personality characteristics. In village dogs, wolf ancestry is enriched at olfactory receptor genes, suggesting adaptive introgression for sensory acuity that may have helped these free-living dogs survive in more challenging environments. In total, dog-wolf admixture has likely been an important factor in shaping the evolution of modern dogs.

Dogs exhibit an exceptional range of morphological diversity as a result of their long-term association with humans. Attempts to identify when dog morphological variation began to expand have been constrained by the limited number of Pleistocene specimens, the fragmentary nature of remains, and difficulties in distinguishing early dogs from wolves on the basis of skeletal morphology. In this study, we used three-dimensional geometric morphometrics to analyze the size and shape of 643 canid crania spanning the past 50,000 years. Our analyses show that a distinctive dog morphology first appeared at about 11,000 calibrated years before present, and substantial phenotypic diversity already existed in early Holocene dogs. Thus, this variation emerged many millennia before the intense human-mediated selection shaping modern dog breeds beginning in the 19th century.

Wild dogs (including dingoes, modern dogs and their hybrids; Canis familiaris) and European red foxes (Vulpes vulpes) are significant environmental and agricultural pests in many parts of Australia. A concerted effort to reduce canid abundance was declared in the early 1900s and ultimately drove the rapid development of new baiting products, best-practice guidelines and improved management. Here, we discuss the evolution of canid management and the current interest by some to use manufactured baits to control canids within production and conservation landscapes. We describe several knowledge gaps surrounding the use of manufactured baits, including questions around aerial baiting efficacy, non-target impacts and the matrix viability. We also propose key research questions that will need to be addressed for us to fully understand the management applications and implications of manufactured baits in effective and integrated management practices.

Modern dog breeds show a trend towards shorter muzzles in the Western world. Using an international online questionnaire (N = 780), we examined how muzzle length, as the sole varying feature, influenced visual preference for dogs, using digitally morphed images of the same individuals. We investigated how preferences for shorter muzzles were influenced by demographics, personality, pre-existing attitudes towards brachycephalic dogs, awareness of health issues, and desired dog traits. Shorter muzzles were generally preferred. Associating more health problems with brachycephaly was negatively associated with preference for shorter muzzles, except among those with positive attitudes towards brachycephalic dogs. Preference was positively associated with positive attitudes towards brachycephalic dogs, older age, conscientiousness, extraversion, and appreciation of aesthetics; and negatively associated with dog-related professional expertise, openness, and a liking for control in dog keeping. Among respondents without prior attitudes, preference was positively linked to viewing the ideal dog as childlike, and negatively to valuing a humorous personality in the ideal dog. Our results show how age, dog-related profession, personality, health awareness, and attitudes towards brachycephalic dogs and the ideal dog intersect to shape preferences for shorter muzzle length. Our findings support the notion that individuals preferring shorter muzzles may prioritise aesthetic traits over health concerns.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-16562-9.

Runs of homozygosity (ROH) are genomic regions that arise when two copies of identical haplotypes are inherited from a shared common ancestor. In this study, we leverage ROH to identify associations between genetic diversity and non-disease phenotypes in Canis lupus familiaris (dogs). We find significant association between the ROH inbreeding coefficient (FROH) and several phenotypic traits. These traits include height, weight, lifespan, muscled, white coloring of the head and chest, furnishings, and fur length. After correcting for population structure, we identified more than 45 genes across the examined quantitative traits that exceed the threshold for suggestive significance. We observe distinct distributions of inbreeding and elevated levels of long ROH in modern breed dogs compared to more ancient breeds, which aligns with breeding practices during Victorian era breed establishment. Our results highlight the impact of non-additive variation and of polygenicity on complex quantitative phenotypes in dogs due to domestication and the breed formation bottleneck.

The Qimmeq (Greenland sled dog) has worked continuously with the Inuit in Greenland for more than 800 years. However, they now face drastic population declines caused by climate change, urbanization, and competition from snowmobiles. This study sequenced 92 modern and ancient genomes to investigate how centuries of isolation shaped the regional Qimmeq populations and the impact of European contact. We found distinct regional populations and evidence for two migrations of dogs into Greenland with the Inuit from Canada. Furthermore, we found that there is minimal European ancestry in present day Qimmit and limited recent inbreeding despite low heterozygosity. These insights are critical for conservation efforts aimed at preserving the Qimmit amid environmental changes and cultural transitions.

IntroductionNatural eyelid conformation is essential for normal function and health of the ocular surface. However, many modern dog types are deliberately bred for abnormal eyelid conformation associated with severe health and welfare issues. This study aimed to report the prevalence, demographic risk factors and clinical management under primary veterinary care for conformational eyelid disorders in dogs.MethodsThe study explored the anonymised clinical records of all dogs under UK primary veterinary care within the VetCompass Programme during 2019. Risk factor analysis used multivariable logistic regression modelling.ResultsFrom 2,250,417 dogs under primary veterinary care in 2019, the analysis included a random sample of 3,029 confirmed conformational eyelid disorder cases that included 2,752 (90.86%) entropion and 344 (11.36%) ectropion cases. After accounting for the subsampling process, the annual prevalence for overall conformational eyelid disorder in dogs was 0.36% (95% CI: 0.35–0.37). The annual prevalence for entropion in dogs overall was 0.33% (95% CI: 0.32–0.34). Breeds with highest annual prevalence for entropion were Shar-Pei (15.41%, 95% CI 14.00–16.91), Chow Chow (9.28%, 95% CI 7.64–11.14) and Neapolitan Mastiff (6.88%, 95% CI 3.02–13.14). The estimated annual prevalence for ectropion in dogs overall was 0.04% (95% CI: 0.04–0.05). Breeds with the highest annual prevalence for ectropion were Neapolitan Mastiff (4.30%, 95% CI 1.41–9.77), Saint Bernard (1.72%, 95% CI 0.86–3.05) and Basset Hound (1.59%, 95% CI 0.94–2.49). Surgical management was carried out for 414/2275 (18.20%) of the incident (2019) entropion cases and 12/305 (3.93%) of the incident (2019) ectropion cases.ConclusionsNormalisation of conformation-related health issues in certain high profile dog breeds have been discussed as a canine welfare priority for over half a century. The current results suggest that substantial work remains to be done to ensure good innate health for all dogs.

This review examines modern companion dog keeping from both biological and cultural evolutionary perspectives. Dog keeping is explored as a trait that has evolved from being adaptive, contributing to the survival and prosperity of human populations, to possibly being neutral or even maladaptive in modern contexts on the population level. Currently, many people in Western cultures regard dogs as family members or "fur babies", even though investing money, time, and emotional commitment in them does not directly increase biological fitness. This new kinship can be better understood through a cultural evolution framework, which is compared to the biological (Fisherian) runaway model to understand how human behaviours can evolve beyond their original utility. For future studies, the review proposes exploring whether and how well dogs can be substitutes for human relationships, their impact on human fertility and social networks, who benefits from dog keeping, and for whom keeping a dog is unnecessary or harmful.

Archaeological and palaeogenomic data show that dogs were the only domestic animals introduced during the early peopling of the Americas. Hunter–gatherer groups spread quickly towards the south of the continent, but it is unclear when dogs reached Central and South America. To address this issue, we generated and analysed 70 complete mitochondrial genomes from archaeological and modern dogs ranging from Central Mexico to Central Chile and Argentina, revealing the dynamics of dog populations. Our results demonstrate that pre-contact Central and South American dogs are all assigned to a specific clade that diverged after dogs entered North America. Specifically, the divergence time between North, Central and South American dog clades is consistent with the spread of agriculture and the adoption of maize in South America between 7000 and 5000 years ago. An isolation-by-distance best characterizes how dogs expanded into South America. We identify the arrival of new lineages of dogs in post-contact South America, likely of European origin, and their legacy in modern village dogs. Interestingly, the pre-contact Mesoamerican maternal origin of the Chihuahua has persisted in some modern individuals.

Although domestic dogs were the first domesticated species, the nature of dog domestication remains a topic of ongoing debate. In particular, brain and behavior changes associated with different stages of the domestication process have been difficult to disambiguate. Most modern Western breed dogs possess highly derived physical and behavioral traits because of intense artificial selection for appearance and function within the past 200 years. In contrast, premodern dogs, including primitive/ancient breeds, village dogs, and New Guinea Singing Dogs, have undergone less intensive artificial selection and retain more ancestral characteristics. Consequently, comparisons between modern and premodern dogs can shed light on brain and behavior changes that have occurred recently in the domestication process. Here, we addressed this question using a voxel-based morphometry analysis of structural MRI images from 72 modern breed dogs and 13 premodern dogs (32 females). Modern breed dogs show widespread expansions of neocortex and reductions in the amygdala and other subcortical regions. Furthermore, cortical measurements significantly predicted individual variation in trainability, while amygdala measurements significantly predicted fear scores. These results contrast with the long-standing view that domestication consistently involves reduction in brain size and cognitive capacity. Rather, our results suggest that recent artificial selection has targeted higher-order brain regions in modern breed dogs, perhaps to facilitate behavioral flexibility and close interaction and cooperation with humans.

Wolves are among the earliest animals to be domesticated. However, the mechanism by which ancient wolves were domesticated into modern dogs is unknown. Most of the prevailing domestication hypotheses posit that humans selectively bred wolves that were more docile. However, a competing hypothesis states that wolves that were less hostile towards humans would essentially domesticate themselves by naturally selecting for tamer wolves since that would allow for easier access to food from human settlements. A major critique of the latter hypothesis is whether evolution by this natural selective pathway could have occurred in a sufficiently short time span. Simulating the process would help demonstrate if such an objection is sufficient to dismiss this hypothesis. Thus, we constructed an agent-based model of the evolution of a single trait, a measure of human tolerance, in canines to test the merit of the time constraint objection. We tested scenarios both with and without mate preference to provide a potential sexual selective force. We used fecundity and mortality rates from the literature for validation. Hartigan's dip test of unimodality was used to measure if and when divergence of populations occurred. Our results indicate that the proto-domestication hypothesis cannot be rejected on the basis of time constraints.

Background/Objectives: The domestication of the grey wolf (Canis lupus) and subsequent creation of modern dog breeds have significantly shaped the genetic landscape of domestic canines. This study investigates the genomic effects of hybridization and breeding management practices in two hybrid wolfdog breeds: the Czechoslovakian Wolfdog (CSW) and the Saarloos Wolfdog (SAW). Methods: We analyzed the genomes of 46 CSWs and 20 SAWs, comparing them to 12 German Shepherds (GSHs) and 20 wolves (WLFs), which served as their ancestral populations approximately 70-90 years ago. Results: Our findings highlight that hybridization can increase genetic variability and mitigate the effects of inbreeding, as evidenced by the observed heterozygosity levels in both wolfdog breeds. However, the SAW genome revealed a higher coefficient of inbreeding and longer runs of homozygosity compared to the CSW, reflecting significant inbreeding during its development. Discriminant Analysis of Principal Components and fixation index analyses demonstrate that the CSW exhibits closer genetic proximity to the GSH than the SAW, likely due to differences in the numbers of GSHs used during their creation. Maximum likelihood clustering further confirmed clear genetic differentiation between these hybrid breeds and their respective ancestors, while shared ancestral polymorphism was detectable in all populations. Conclusions: These results highlight the role of controlled hybridization with captive-bred wolves and peculiar breeding strategies in shaping the genetic structure of wolfdog breeds. To ensure the long-term genetic health of these breeds, it is recommended to promote adequate and sustainable breeding practices to maintain genetic diversity, minimize inbreeding, and incorporate the careful selection of unrelated individuals from diverse lineages, while avoiding additional, uncontrolled crossings with wild wolves.

Genomic reconstruction reveals impact of population management strategies on modern Galápagos dogs.

Dog. Specifically created to save its master's life. - (The dog is the ideal) Friend of man, (because it is his devoted slave) (source: Gustave Flaubert, Dictionnaire des Idées Reçues). But is man the best friend of the dog? This question is legitimate when we consider living situations to which modern domestic dogs are exposed. They often do not satisfy basic animal needs. In this narrative review, the author revisits the history of the dog's presence alongside humans, in the light of current knowledge. The modern dog (breed standards and their interests in canine research) and its breeding strategy, including extreme breeding, will then be given particular attention. Dysfunctional human psychological processes will be explored to make it possible to grasp why the breeding of the modern dog is undergoing such a transformation. Finally, based on these factual and conceptual insights, suggestions to improve canine welfare will be proposed. To be effective, all these must be assessed against real-world conditions.

Deciphering the genetic basis of behavioral traits in dogs: Observed-trait GWAS and latent-trait GWAS analysis reveal key genes and variants

Cranial suture obliteration patterns as an ageing method for dog crania

Multiple ancestries and shared gene flow among modern livestock guarding dogs