Dog owners in North America are keenly aware of the vast array of market options when it comes to feeding your dogs. There are those who believe in all-raw food diets, meat-only diets, and mixed vegetable, grain, and meat diets, to name only a few, and of course an even wider suite of companies willing to sell you products to meet these beliefs. In many other regions of the world, dogs eat entirely differently, often on the same food items eaten by people, in some cases even in societies which are are strictly vegetarian. Dogs virtually everywhere sometimes feed themselves entirely through scavenging and hunting. Further, dogs within a given society might be fed different foods depending on how humans tend to use them–if they are used for highly strenuous tasks such as chasing down prey, or if the dogs are to be used as human food, for example.
Stable carbon and nitrogen isotope analysis of human bones is a common technique for exploring ancient peoples’ diets. These analyses involve destructive studies of small pieces of bone, and they generate measurements of the ratios of the isotopes present, which then can be used to assess the trophic level of an individual–basically, where they were within the food chain. These studies are best at understanding the protein portion of the diet, and are particularly useful for identifying the use and importance of groups of food items such as marine fish and shellfish, freshwater fish, terrestrial herbivores, or some plants, such as millet. Complex mathematical models can be used on these diet data, and with such values for potential food items, to produce probability models of the overall structure of the diet.
Stable isotope values for a suite of Middle Holocene humans and canids (dogs and wolves) from the Lake Baikal region of Siberia, Russia. In brief, the figure shows that the human values fall in two clusters, with those to the upper right having more fish-rich diets than those to the lower left. The dog diet points tend to be slightly lower on the nitrogen scale when compared to human data points with similar carbon values, particularly to the right side of graph.
Such analyses have been conducted many times on ancient dog bones, but with no real interest in dog diets and provisioning practices. Instead, such studies are done where human remains are unavailable for study, or it is socially unacceptable to study human remains. The dogs then become stand-ins for their people, because it is generally thought that in many prehistoric settings, dog diets will closely follow those of local people. Generally, this appears to hold true–people food was dog food. In cases where there are both human and dog isotope values, however, subtle differences are sometimes noted, suggesting dogs were eating slightly different diets than their human counterparts.
Our stable isotope projects focus not on using dogs as proxies for understanding human diets but rather on how dogs were being fed, or how they were feeding themselves. We focus on how dog diets change through time within particular regions, and how dog diets might relate to the daily tasks they were involved in, such as pulling sleds. Further, we are interested in exploring how dog diets varied within particular sites and regions–did their diets differ by sex or age, or are there dietary indicators that some dogs were brought into the region from elsewhere just prior to their deaths (they have non-local diets)? Were dogs fed differently when they were being raised as sources of human food?