Answer by Richard Barrios:
I think Native Americans sum it up the best in this story that I really love.
The earth trembled and a great rift appeared, separating the first man and woman from the rest of the animal kingdom. As the chasm grew deeper and wider, all the other creatures, afraid for their lives, returned to the forest — except for the dog, who after much consideration leapt the perilous rift to stay with the humans on the other side. His love for humanity was greater than his bond to other creatures, he explained, and he willingly forfeited his place in paradise to prove it……Native American folktale…an Ojibway tale
Source: What is the Native American legend on how the dog became man's best friend
Humans sometimes share a unexplainable bond with dogs. Dogs seem to understand us better then most humans and sometimes better then our closest human friends. Whether its their sense of smell, heightened primal awareness or just in their DNA. Whatever it is, I really don't care if it ever can be explained, its just wonderful that it's real.
On a personal note. I seen my Dad cry only a handful of times in my life. One was when our dog passed away at my dad's feet.