The evolution of dog diet and foraging: Insights from archaeological canids in Siberia.

Research on the evolution of dog foraging and diet has largely focused on scavenging during their initial domestication and genetic adaptations to starch-rich food environments following the advent of agriculture. The Siberian archaeological record evidences other critical shifts in dog foraging and diet that likely characterize Holocene dogs globally. By the Middle Holocene, body size reconstruction for Siberia dogs indicates that most were far smaller than Pleistocene wolves. This contributed to dogs' tendencies to scavenge, feed on small prey, and reduce social foraging. Stable carbon and nitrogen isotope analysis of Siberian dogs reveals that their diets were more diverse than those of Pleistocene wolves. This included habitual consumption of marine and freshwater foods by the Middle Holocene and reliance on C4 foods by the Late Holocene. Feeding on such foods and anthropogenic waste increased dogs' exposure to microbes, affected their gut microbiomes, and shaped long-term dog population history.

Modern Siberian dog ancestry was shaped by several thousand years of Eurasian-wide trade and human dispersal.

Dogs have been essential to life in the Siberian Arctic for over 9,500 y, and this tight link between people and dogs continues in Siberian communities. Although Arctic Siberian groups such as the Nenets received limited gene flow from neighboring groups, archaeological evidence suggests that metallurgy and new subsistence strategies emerged in Northwest Siberia around 2,000 y ago. It is unclear if the Siberian Arctic dog population was as continuous as the people of the region or if instead admixture occurred, possibly in relation to the influx of material culture from other parts of Eurasia. To address this question, we sequenced and analyzed the genomes of 20 ancient and historical Siberian and Eurasian Steppe dogs. Our analyses indicate that while Siberian dogs were genetically homogenous between 9,500 to 7,000 y ago, later introduction of dogs from the Eurasian Steppe and Europe led to substantial admixture. This is clearly the case in the Iamal-Nenets region (Northwestern Siberia) where dogs from the Iron Age period (∼2,000 y ago) possess substantially less ancestry related to European and Steppe dogs than dogs from the medieval period (∼1,000 y ago). Combined with findings of nonlocal materials recovered from these archaeological sites, including glass beads and metal items, these results indicate that Northwest Siberian communities were connected to a larger trade network through which they acquired genetically distinctive dogs from other regions. These exchanges were part of a series of major societal changes, including the rise of large-scale reindeer pastoralism ∼800 y ago.

Three-Dimensional Geometric Morphometric Analysis of Fossil Canid Mandibles and Skulls.

Much of the fossil record for dogs consists of mandibles. However, can fossil canid mandibles be reliably identified as dogs or wolves? 3D geometric morphometric analysis correctly classifies 99.5% of the modern dog and wolf mandibles. However, only 4 of 26 Ust'-Polui fossil mandibles, a Russian Arctic site occupied from 250BCE to 150CE, were identified as dogs and none of the 20 Ivolgin mandibles, an Iron Age site in southern Russia, were identified as dogs. Three of the Ust'-Polui mandibles and 8 of the Ivolgin mandibles were identified as wolves. In contrast, all 12 Ivolgin skulls and 5 Ust'-Polui skulls were clearly identified as dogs. Only the classification of the UP6571 skull as a dog (Dog Posterior Probability = 1.0) was not supported by the typical probability. Other evidence indicates these canids were domesticated: they were located within human dwellings, remains at both sites have butchery marks indicating that they were consumed, and isotope analysis of canid and human remains from Ust'-Polui demonstrate that both were consuming freshwater protein; indicating that the humans were feeding the canids. Our results demonstrate that the mandible may not evolve as rapidly as the cranium and the mandible is not reliable for identifying early dog fossils.