As hunters, fetchers, and vigilant protectors, dogs have honed a wide array of specialized skills through centuries of breeding.
In a new study, scientists say evidence of all this human intervention can be seen at a deeper level than simply how the animals use their snouts and paws:
It shows up on MRIs of their brains.
The authors analyzed brain scans of 62 dogs from 33 breeds, identifying six broad "networks" of interconnected brain regions related to such traits as smell, vision, and navigation -- and finding that these networks were larger or smaller in various animals as a result of breeding.
It was no surprise to find evidence that humans had shaped dogs' brains, but many of the details were unexpected, said lead author Erin E. Hecht, an assistant professor in Harvard University's department of human evolutionary biology.
In hunting dogs, for example, the regions of the brain devoted to detecting sights and smells were roughly the same size no matter which sense a particular breed relied upon to detect its prey.
Instead, the scans revealed differences in the brain regions that handle making decisions about those sights and smells, Hecht said.
"It seems like those behaviors are more related to higher-order regions of the brain," she said.
Hecht, whose website says that her miniature Australian shepherds, Lefty and Izzy, "are mostly good," was joined in the research by scientists from Emory, Stony Brook, and Michigan State Universities and the University of Georgia.
The authors analyzed MRIs from animals that had come in for a neurological exam but were found by veterinarians to have no brain abnormalities. All were sedated for the screening procedure.