With domestication, dogs became smaller and changed their eating habits significantly. They preferred to hunt smaller prey animals and increasingly fed on what people left over or put in front of them. This is what an international team of researchers reports after analyzing finds at archaeological sites in Siberia.
"Some of these adaptations helped dog populations expand and the animals develop their roles as hunters, herding dogs, and sled drivers for which they are historically known in Siberia and elsewhere," write researchers led by Robert Losey of the University of Alberta ( Canada) in the journal Science Advances. Other developments have been harmful, such as more frequent parasite infections that the dogs caught with the food.
About 700 million dogs lived on earth, the team writes. Although there is a wide variety of dog food products, most dogs are not fed by humans. They lived wild, fed on refuse and hunted cattle or smaller animals. Their eating habits are diverse - and a consequence of domestication by humans.
This began in Eurasia 40,000 years ago when the evolutionary lineage of dogs branched off from wolves. It is generally assumed that the ancestors of the domestic dog first looked for food in the vicinity of humans. Later, with the advent of agriculture, some dogs would also have developed the ability to better digest starch. Dogs with the appropriate genetic basis appeared about 7000 years ago.
The researchers are now investigating other changes that are associated with dogs living with humans, such as the development of body size and weight.
The analysis showed that the dogs became smaller and smaller during the Holocene, which began a good 11,000 years ago. While wolves usually weigh more than 30 kilograms, the average weight of 199 dogs from Siberia examined was just over 16 kilograms.
The researchers write that there was a similar development in other regions. Biting power and hunting radius would also have decreased with smaller bodies, which would have made it more difficult for them to hunt larger prey and might have kept dogs close to humans.
Isotope analyzes of the bones provided information about the diet of the animals. The scientists studied 143 dogs from a time between 9000 and 500 years ago that had lived near humans on the sea coast, at lakes or with hunters, farmers and pastoralists. The respective habitat of the dogs is reflected in their diet: the researchers found evidence of a diet containing fish in dogs that had lived near bodies of water.
Earlier - and today - wolves, on the other hand, mainly hunt large herbivores and hoofed animals, fish play at most a subordinate role in their diet. Dogs that had lived with farmers and pastoralists showed evidence of a highly variable diet, presumably reflecting the varied diets of humans.
The data indicated that dogs had developed a certain dependence on humans by at least 7,400 years ago and were either fed by them or ate their leftovers.
With the change in diet, more and more parasites and other pathogens passed to dogs, as studies of leftover faeces show. This probably increased their mortality, at least temporarily, and affected population development, the researchers write.
