Most of the sources of information about the Thoroughbred declare that there are three founding fathers of the breed. These are the three lines that were still active when bloodstock writing became important toward the middle and end of the 19th century. There are actually quite a few more stallions who played a part in the early formation of the breed, and many of them are still in pedigrees, far back and of little specific consequence to horses today.
As has become increasingly clear over the past century, the “three lines” is pretty much a thing of the past also. At least in the male line. That spot is nearly the private preserve of the Darley Arabian – Eclipse – Bend Or – Phalaris set of horses that make up about 90 percent of the male line in Thoroughbreds today.
Although the Godolphin Arabian is still out there, the best lines have nearly all retreated into the inner reaches of pedigree, and Man o’ War’s branch of the line through In Reality – Relaunch – Tiznow seems destined for the history books unless something quite unexpected happens to resurrect the line. Again.
The line from the Byerly Turk has been lingering for a century, and it lost its last great chestnut hope when Precisionist, a champion sprinter who stayed 10 furlongs and was tough as hickory, proved all but sterile at stud.
Regarding sire lines, however, the “influence” of those lines is still around. These three and all those others that have died out in male line are still represented among the internal lines of pedigrees, so long as the performance of those strains continues to justify people using them. It’s all about probability and opportunity.
The hard fact is that most stallions or stallion prospects do not have the genetic consistency to sire a reasonable proportion of good, highly successful racers. That’s the probability side that allows horses like Danzig, Mr. Prospector, and Phalaris to come up trumps when they aren’t world champions. Instead, they are pretty good racehorses but are genetic champions.
Opportunity is the other side of the coin. Without a fair number of reasonably good mares, a stallion cannot have consistent, high-quality success. It wasn’t a hindrance that Phalaris became a miracle sire when based at Stanley House; nor did standing at Claiborne prove a barrier to Danzig. Mr. P started in Florida, where he was widely appreciated for speed and pedigree, and with immediate success, Mr. P went to Kentucky to stand at Claiborne for the rest of his long career at stud.
As a result of the chance association of genes and overall tendency for this to regress to the mean, most stallion prospects fail; most male lines die out. It’s not a popularity contest, at least not when the runners come to the races.
So the effect of male lines dying out is inevitable. The male line is the most competitive position in a pedigree. Only the most successful contemporaries continue in the male line. The preference of breeders for the most successful stallions means that lesser sires will not get sons, will die out in the male line. Both of the lesser male lines were tenuous more than a century ago. Then Hurry On in Europe and Fair Play in the States set the Godolphin Arabian line alight once more.
With broad representation for those three lines among horses going to stud, as well as the ones before them, the lines would not die out as easily. They would simply lie in abeyance until the next genetically gifted sire came into service. But in the practical world of breeding horses, the earliest lines died out quickly because so few stallions were actively important; nobody cared much at the time, nor should they have done. The majority of those old sires, and many more modern ones, still continue along the internal lines of descent. Probability has winnowed out the population in the male line, however.
So a perceived lack of diversity is not that, in fact.
The three lines that survived did so by chance. They sired good racers who sired good racers, whose grandsons sired a great racer, etc. The odds of chance decree that most will lose, but contrarily, they decree that some will win. Someone will win the Derby every year, no matter how little deserving compared to Ormonde, Hyperion, or Sea-Bird.