We have no idea whether thoroughbred horses love to race. We like to think they do, and maybe, on a glorious spring day in Triple Crown season, a 40-mile-an-hour run around a dirt oval under a jockey's whip in front of a cheering crowd really does feel wonderful to an animal that has, after all, been bred and trained for just such an activity.

But we don't know, and it is hard to sustain an illusion of joy for anyone who has sat in a nearly deserted grandstand on a dreary afternoon, watching horses cross the finish line covered with mud from a sloppy track. And do even champions really love being loaded into vans or onto airplanes for a trip to a distant racetrack when the reward, for them, is little more than a blanket of roses?

I have been a racing fan for years, and my point is not that horse racing is cruel or morally ambiguous. I will let others make that argument, as many have in the past week. Yes, we feel a special obligation to these fragile, beautiful creatures whom we place in harm's way for our own sporting pleasure. And yes, when their perfection is marred, we shudder as we would at the destruction of a work of art. But I think the sense of obligation runs at a deeper, even subliminal level. We are responsible for racehorses because we in a very real sense created them.

Today's thoroughbreds are a result of more than 300 years of selective breeding that has carried them very far from their roots on the steppes and deserts of the Middle East. Every thoroughbred is descended from one of three stallions, the Darley Arabian, Godolphin, and the Byerly Turk, brought to England toward the close of the 17th century and bred to mares initially under the patronage of King Charles II. A great-great-grandson of the Darley Arabian, bred by a son of King George II, was born during a solar eclipse in 1764 and named Eclipse. An undefeated champion on the track, he sired 344 winners, and his powerful bloodline literally eclipsed all others. In fact, 95 percent of the thoroughbreds alive today are his descendants.

During the ensuing centuries, theories about the best strategies for fulfilling the injunction to "breed the best to the best" have come and gone, but almost nothing has been left to chance. Barbaro's sire, Dynaformer, stands for a stud fee of $100,000. Human intervention has been so pervasive that on some level these are scarcely horses any longer but centaurs, part equine and part human, their lives so intermingled with ours that there is no separating the two.