Many of the inherited variations that make the dog paedomorphic to the wolf may involve neurohumors and glands. Studies of “domesticated foxes”, bred within a human lifetime, show significant increases in serotonin and significant decrease in corticosteroids. The specially bred foxes have floppy ears and bark. The current hypothesis is that similar changes happened in the ancestors of the dog.
This is on the net. However, I can’t give links. I will give the reference to the
article and a quotation from the abstract.
“The Domestic Savage” in Scientific American September 2003.
“The most famous study on selective breeding for passivity began in 1959 by Russian geneticist Dmitri Belyaev of the Institute of Cytology and Genetics in Siberia. It continues today under the direction of Lyudmila N. Trut. Silver foxes were bred for friendliness toward humans, defined by a graduating series of criteria, from the animal allowing itself to be approached, to being hand fed, to being petted, to proactively seeking human contact. In only 35 generations the researchers produced tail-wagging, hand-licking, peaceful foxes. What they also created were foxes with smaller skulls, jaws and teeth than their wild ancestors.
The Russian scientists believe that in selecting for docility, they inadvertently selected for paedomorphism — the retention of juvenile features into adulthood — such as curly tails and floppy ears found in wild pups but not in wild adults, a delayed onset of the fear response to unknown stimuli, and lower levels of aggression. The selection process led to a significant decrease in levels of stress-related hormones such as corticosteroids, which
are produced by the adrenal glands during the fight-or-flight response, as well as a significant increase in levels of serotonin thought to play a leading role in the inhibition of aggression. The Russian scientists were also able to accomplish what no breeder had ever achieved before — a lengthened breeding season.”
I think this article will address your original question, which was why dogs bark
more than wolves. Of course, you may have a few more questions after you read
it.