303 Diets of Neolithic dogs

Abstract The history of our modern-day pet dogs started around 40,000 yr ago in the Paleolithic era when humans had a hunter-gatherer lifestyle. During the period that humans became more sedentary agriculturalists, the Neolithic era, the food sources available for the early (proto) dogs living with humans also changed. The profound shift in the diet of dogs with increased amounts of cereal grains throughout this era is reflected in the genome of the dog, suggesting an enhanced digestive capacity to digest starch. The foraging strategies these dogs developed to meet energy and nutrient requirements are, however, still understudied. We therefore aimed to advance our understanding of the diets of Neolithic dogs. Data from various publications that included stable isotope, coprolite and observational analyses were retrieved and used to define hypothetical foraging strategies (scenarios). These strategies included commonly reported starch and protein sources and it was investigated how dogs met their dietary needs in terms of metabolizable energy (ME), nitrogen and indispensable amino acids. The ME contents were estimated based on the chemical composition using modified Atwater factors. Stable isotope and coprolite analyses suggest that Neolithic dogs had a highly variable diet, with a large variety in food items and differing ratios of plant-based food sources (e.g., millet, maize) to animal-based food sources (e.g., livestock, rodents). Observations support these findings with e.g. plant-based sources contributing 24 to 66% of the biomass and animal-based sources contributing 17 to 54%. Moreover, human feces are often noted in the literature as a food source for dogs with estimates 17 to 24% of the dietary biomass consumed. The ME requirement is shown to be easily met with the addition of animal-based feedstuffs and nitrogen requirements were always met if the dietary intake was sufficient to cover for minimum ME. However, several amino acids (e.g., Met and Cys) were limiting, if diet contained too little quantities of animal-based feedstuffs. Data from various publications and such scenarios provide context for the nutrition of present-day dogs and coprophagy commonly observed. In conclusion, Neolithic dogs developed an opportunistic foraging strategy resulting in diverse omnivorous diets. To support indispensable amino acids, dogs could not thrive solely on cereal-based diets but required to supplement these with animal-based food sources including human feces.