Why do horses allow humans to ride them? They don't have to, you know. While humans may have delusions of control and dominance, the truth is they remain in the saddle only as long the horse permits it. Horses know they are quite able to rid themselves of these puny ape-like hitchhikers any time they want.

For us, riding horses seems like a perfectly natural thing. The words "horse" and "rider" go together like "soap and water" or "love and marriage" or "Bill and Monica" or "MTV and turn off that garbage, kids". We are used to seeing people on horses and take it for granted that it's appropriate.

The image of people riding horses is deeply ingrained in our culture. In old cowboy movies for example, you never saw a guy without his horse. The thought of a cowboy trudging from town to town on foot is almost un-American. A cowboy and his horse were inseparable. It was almost as if they were just different parts of the same creature.

When I was kid, the idea of an inseparable union between horse and rider was reinforced by my miniature army of plastic horse-soldiers. Each soldier/horse duo was literally one piece. You couldn't yank the guy off his horse. They were stuck like that until the end of time. When my army made camp for the night, each horse-soldier had to sleep with one leg pinned beneath his horse. I don't think the horses were too comfortable, either.

I also remember our family taking Sunday drives in the country. From the back seat I would catch sight of horses in a field and wonder where the riders where. "Where's the guys?" I asked myself. "How did the horses get away from the guys?" "These horses are lost," I surmised.

Some people believe that it is natural for humans to ride horses because of the way horses are shaped. The animal's middle part is lower than the front and rear thus providing a perfect place for people to sit. Our species is always looking for a good place to sit.

While it's true that the contour of a horse's back makes it practical for humans to ride them, using a living thing simply because it has convenient shape can be an insult to the creature's dignity. I know this from personal experience. When my daughter, Hiliary, was two, she developed a habit of wrapping her arms around my left leg just below the knee and riding all over the house on top of my foot. It was a simple matter of her busy little mind noting the manner in which my foot joined my leg at the ankle. "I could ride that thing," she decided. Limping from the living room to the kitchen and up the stairs, I reluctantly morphed into The Amazing Human Sulky.

So why do horses put up with it? Is it out of fear? Are they in awe of us? Do they actually buy that bit about us being smarter than they are?

A clue to this mystery may be found in the way horses organize themselves socially. Yes, horses organize themselves socially. For those of us who dismiss horses as mindless, fear-driven creatures, the realization that horses organize themselves socially can be unsettling. When we see them collected in their groups, we have to wonder what they're up to. Are they planning to make a run for it? Or are they just talking about food? Perhaps they're preparing to attack.

What they are really doing in those little gatherings is making friends. While it is true that whenever a group of horses are put together they establish a pecking order, observers are discovering that this order of dominance is not fixed. Like truth in the Clinton Administration, it changes depending upon the situation. More importantly, it changes according to the relationship between individual horses. Just like humans (and presidents), horses display preferences for certain companions. In other words, they make friends. And the bonds of these friendships are strong enough to transcend the normal pecking order.

Thus horse society is organized in the same way neighborhood beer drinking buddies are organized: friendly-like. It has more to do with companionship than dominance. Horses are nice creatures at heart.

And this is why horses let us ride them: they're just being neighborly.