In dogs (and other animals), parents pass on 50% of their genetic makeup to their young. Puppies, however, inherit randomly available DNA segments. The dog's breed is the biggest determinant of litter size. In general, large dogs have larger litters because, biologically, they can safely carry more puppies.
Researchers hid a treat in one of the two bowls, then gave a clue by pointing and looking at each dog or wolf cub to help them find the treat. Fundamentally, Canine Companions also maintains extensive information on the pedigree of each dog that dates back decades, which facilitated the genetic aspect of the study. Most puppies were tested at seven or eight weeks of age, and most wolf pups were tested between nine and 13 weeks of age. MacLean and colleagues analyzed how 2-year-old children, dogs and chimpanzees performed on comparable batteries of tests designed to measure various types of cognition.
Analysis of the genomes of the two species has revealed differences that some scientists believe are the result of dogs being subject to artificial selection imposed by humans. Now, a new study, published today in the journal Current Biology, finds that even 8-week-old puppies with little exposure to humans can understand how to signal and display sophisticated levels of social cognition in other tests. Humans have control over certain aspects of when and how a dog is raised that can affect litter size, but there are limits. In fact, the evolution of most dog breeds is a relatively recent phenomenon, which began with selective breeding practices over the past 200 years.
Bray says she and her co-authors are already working on a follow-up genomic study of Canine Companions dogs that will look for genes that correlate with the same types of social cognition explored in the present work. Beyond filling a missing part of the domestication story, identifying the genetic basis of this social skill set in dogs could one day help us breed even more successful service dogs, MacLean says. In both tasks, puppies arrived at the correct cup an average of 67 percent of the time, much better than the 50 percent accuracy one would expect if only chance were responsible for the correct answers. But did dogs develop these traits through evolution or is it the product of thousands of years of domestication? It seems that domestication, which began 14,000 years ago, resulted in a relaxation of the selective forces typical of nature (forces that continued seriously on wolves), as well as an increase in variability in the dog's genome compared to the genome of its ancestral lineage (Björnerfeldt et al.
At this age, the puppies had spent almost every minute of the day with their mother or litter mates.
