And as humans grow more fond of affectionate pets, canines are becoming more sensitive to this hormone.
The team timed the animals to see how long it took for them to ask their owners to help.
This experiment reaffirmed the notion that oxytocin levels greatly influence a dogs social skills and relationship with humans.
Their sensitivity to social behavior is partially related to their genes.
And increasing friendliness seems to have changed these dogs biology, just as it did thousands of years ago.
Humans could supplant pack leaders and assert dominance, training the nascent dogs to be subordinate from puppies.
The second wave of domestication occurred after the Industrial Revolution.
As disposable income increased, people began breeding dogs for specific physical traits that reflected their status.
Check out the results:
