There are innumerable breeds of dogs in existence today. From giant Great Danes to tiny chihuahuas. Each breed looks distinct from the others, and have distinct habits and mannerisms...and yet they all descended from the same wild beast: the wolf!
Bare with me, this is all going somewhere relative to humankind...
So how did we go from this:
The common theory is that early man came upon a litter of wolf puppies, perhaps accidentally, and selected a puppy to keep based on friendliness and tameness and discarded the rest. An UNnatural selection, if you will. When that pup had pups, we again selected for tameness, until over the course of generations we ended up with the domesticated dog. In the Soviet Union, an experiment was held on the Silver Fox that attempted to reproduce those same results. Wild Silver Foxes were captured, bred, and then only the most inherently tame pups were bred. In a very short time (relatively speaking) a tame breed of Silver Fox emerged with behavior similar to modern domesticated dogs (i.e. wagging tails, barking, etc.). Even MORE interesting were the differences in morphology/physiology: the dogs began to have mottled, colored fur, etc.
This entire experiment was undertaken by scientists who "were interested in the topic of domestication, and the process by which wolves became tame domesticated dogs. They saw some retention of juvenile traits by adult dogs, both morphological ones such as skulls that were unusually broad for their length, and behavioral ones such as whining, barking, and submissiveness" (wiki, hehe). Much of the behavior we associate with adult dogs, are actually not done by adult wild wolves...these are traits of immature puppies.
So isn't it likely that the same process was undertaken by humankind as we began to organize into large, settled, agrarian societies? As the savage day-to-day struggle to survive became a thing of the past, how likely do you think those most adept at surviving that savage struggle would fit in to the relatively staid life of a farmer? I would contend that those savage men and women most physically and mentally suited to the savage life were ostrasized from society, in effect selecting for those traits of docility and...tameness? Could it be over the course of generations we've become the "puppies" of what humankind once was? And what does that mean for our morphology/physiology? What did that savage human look like?
Don't misunderstand me, society finds certain behaviors unacceptable for a reason, and that is how it should be. Throwbacks in terms of behavior currently exist, and our prison system is full of them. However, just like the wild wolf is smarter and generally stronger and faster than its domesticated bretheren, is there a chance we've also let go of some of these traits along the way? I believe in exercising and eating the way our ancient pre-Agriculture ancestors did, and I think this leads to very pleasant results as our genetics remember a stronger, faster, leaner existance.
"Civilize the mind, but make savage the body." - Chairman Mao