Centuries ago, the world was drastically changed when dog and man joined forces against the world around them. Today, our dogs are still an invaluable part of our daily lives. They greet us with unconditional love after a long, grueling day at work, listen to our problems with judgment-free attention, and get us off the couch and exercising when we least want to but most have to.

But what makes this partnership such a natural one that has lasted for tens of thousands of years? In the grand scheme of things, there are relatively few animals that have found such an honored place in our homes and in our hearts. So why dogs?

Canine critics will say that the man-dog relationship is a self-serving one on both parts. Humans get defense and an almost infallable alarm system, while dog get a warm place to sleep and some free handouts. While that's certainly a bonus for both parties involved, geneticists and behavioral specialists have suggested that it's not the main reason.

All dogs, from huskies and German shepherds to Chihuahuas and terriers, are descended from wolves. Dog skeletons have been found alongside the remains of human settlements as long as 16,000 years ago. It's been suggested that the domesticated dog happened around the same time people started organizing themselves into permanent settlements, rather than the hunter-gatherer types they had previously been. Wild wolves quickly learned where humans would be and what they would be doing, and became accustomed to their presence. Many state parks have signs instructing visitors not to feed the wildlife, because they will lose their fear of humans. It's though that's what gradually happened with wolves. Wolves began to see these funny-looking animals as an extension of their pack, and joined up.

The old theories that dogs were domesticated when wolves were abducted as pups and raised in a human environment just doesn't fly. It's been tried. Add into the equation that ancient peoples probably didn't have time to spend with a helpless puppy -- they were too busy doing other necessary work needed just to survive -- and that theory quickly loses credibility.

Dogs, like their wolf ancestors, are pack animals. Today, this is perhaps most noticeable in homes with more than one dog. Ideally, the human will be the alpha and the dogs should know their place in the ranks beneath them. But among dogs, there will often be a second-in-command, just as there is one that is usually left to pick up the leftovers. When humans try to treat them all the same, chaos can erupt. It's not being cruel, it's respecting the dogs' natural ability to find their own place in the pack. Generally, dogs don't care where they rank, as long as they know they have a place and they belong.

Food is the driving factor behind many of the actions of all living creatures. In the case of dogs, it was a vehicle to help with not only domestication, but the establishment of the pack heirarchy. Humans left scraps behind, which were cleaned up by wolf and later dog companions. This placed human firmly at the top of the pack, where they were joined by the more submissive and less aggressive of the wolves -- those who were more than happy not to be the alphas. These are the wolves from which our modern counterparts are descended.

Modern archaeology seems to agree that we didn't domesticate the dog, but instead that the dog domesticated himself. Looking at the relationship we have with our canine companions today, a lot is explained by this relatively new theory. Many of us have dogs not because of what they do for us, but because of what we are together. Ancient peoples didn't domesticate the dog because they needed help in the hunt or because they needed protection, dogs were domesticated because they expanded their social circle to include humans.

Understanding what made dogs choose to spend much of their time beside human companions can help us better relate to those we share our homes with. The relationship is one of mutual benefits, and those benefits aren't always what they seem at first glance.