After 32 years of the Breeders’ Cup, the patterns of sire lines and female families of the race winners are well established. The Northern Dancer and Mr. Prospector male lines will dominate, and Bruce Lowe female family No. 1 will provide more winners than any other female line. In both cases, the source of the most winners is a numerical advantage in the population. There are more stallions from those sire lines at stud and more broodmares from family No. 1 than from other lines. Obviously, though, there are more Thoroughbreds in the breeding population from those male and female lines for a reason. Historically, those lines have produced more good horses than others, leading to more sires and broodmares from those lines being given opportunities at stud. It is a classic case of Darwinism at work, aided of course by human objectives. At the 2015 Breeders’ Cup at Keeneland, the Northern Dancer (6) and Mr. Prospector (5) lines provided 11 of the 13 Breeders’ Cup winners. As shown in the accompanying table, those victories brought the Northern Dancer male line’s total number of individual Breeders’ Cup winners to 86, with the Mr. Prospector male line in a distant second place at 66. As the table indicates, however, it was not always thus. Looking back to the inaugural Breeders’ Cup in 1984, those two male lines provided three of the seven original Breeders’ Cup race winners. Mr. Prospector himself sired the ill-fated inaugural Sprint winner Eillo, while Northern Dancer’s son Danzig sired the first Juvenile winner, Chief’s Crown, and Northern Dancer’s grandson Lypheor was the sire of the inaugural Mile winner Royal Heroine. Wild Again, the controversial winner of the first Classic, was a son of Icecapade who carried on the male line and was responsible for another Classic winner last year through his son Offlee Wild, sire of Bayern. The first Distaff winner, Princess Rooney, was a granddaughter of Speak John, who has not had a Breeders’ Cup-winning male-line descendant since Meadow Star won the Juvenile Fillies in 1990. The male line of Never Bend’s son Mill Reef, sire of the first Turf winner, Lashkari, has lasted longer, though Lashkari had nothing to do with it. Mill Reef’s fourth-generation male-line descendant Conduit, by Dalakhani, by Darshaan, by Shirley Heights, by Mill Reef, won the Turf in both 2008 and 2009. Outstandingly, the 1984 winner of the Juvenile was the only Breeders’ Cup winner for dual leading sire Exclusive Native, who was by the same sire, Raise a Native, as Mr. Prospector, but his branch of the male line has not survived. All of this history is evidence of how male lines evolve over time, and that continuing evolution was evident at the 2015 Breeders’ Cup. All branches of the Northern Dancer and Mr. Prospector male lines are not created equal. This year, the Fappiano branch of Mr. Prospector provided three Breeders’ Cup winners, matched by the Sadler’s Wells branch of Northern Dancer. In fact, it is probably about time we change the nomenclature from Fappiano to that of his son Unbridled, since all three of those winners are male-line descendants of Fappiano’s 1990 Kentucky Derby and Classic winning son. Despite the good work done by Fappiano’s sons Cryptoclearance, Quiet American, Roy, and Rubiano, Unbridled clearly has become a male-line founder in his own right, and with his outstanding 2015 Breeders’ Cup-winning descendants American Pharoah and Liam’s Map retiring to stud next year, the continued expansion of the Unbridled branch of Mr. Prospector is all but certain. The Northern Dancer male line appears to be evolving into three dominant branches: Danzig, Sadler’s Wells, and Storm Cat, although the Deputy Minister and Nureyev branches still are relatively healthy. All three were represented by Breeders’ Cup winners this year, with War Front’s Juvenile Turf winner, Hit It a Bomb, the only winner for Danzig, whose 19 Breeders’ Cup winners still give him primacy among the branches of sire Northern Dancer’s prolific male line. The Northern Dancers always have been particularly prolific in turf races, and Sadler’s Wells was responsible for two of the winners on grass – Turf winner Found, by his great son Galileo, and Filly and Mare Turf winner Stephanie’s Kitten, by Sadler’s Wells’s grandson Kitten’s Joy. Another grandson of Sadler’s Wells, Medaglia d’Oro, like Kitten’s Joy a son of El Prado, was a top-class dirt horse and has proved a less surface-dependent sire. His daughter Songbird clinched a championship with her dominating performance in the Juvenile Fillies. In a sense, though, the most extraordinary feat by a stallion at the 2015 Breeders’ Cup meeting was a second consecutive Mile win for the offspring of Storm Cat’s son Bernstein. Although Bernstein has been consistently successful in both America and Argentina, he never has been considered a top sire in the land of his birth. Nevertheless, the brilliant filly Tepin’s victory in the Mile followed that of Bernstein’s best son, Karakontie, in 2014. Karakontie finished 11th in the Mile this year. Despite the dominance of Northern Dancer and Mr. Prospector, other sire lines have survived, and two that show strong signs of future expansion provided 2015 Breeders’ Cup winners. Nasrullah’s great-grandson Caro sired the 1985 Mile winner Cozzene, and Caro’s fourth-generation male-line descendant Uncle Mo has made a sensational start at stud this year with six juvenile stakes winners in his first crop, led by the courageous Juvenile winner Nyquist. Uncle Mo’s sire, Indian Charlie, was an outstanding sire, but his previous sons at stud have made little impact. Uncle Mo, however, was easily his best son and looks certain to expand the influence of the Caro male line. Runhappy, determined winner of the Sprint, is from the first crop of 2010 Kentucky Derby winner Super Saver, a male-line descendant of Mr. Prospector’s sire, Raise a Native, through his 1969 Kentucky Derby winner, Majestic Prince. The latter was only moderately successful as a sire, but his best son, Majestic Light, was a better sire. Majestic Light’s Haskell Invitational winner, Wavering Monarch, sired the 1995 champion 2-year-old male Maria’s Mon, whose Kentucky Derby-winning son Monarchos failed at stud, but Super Saver has sired eight stakes winners in his first two crops, including Grade 1 winners Competitive Edge and Embellish the Lace. The 13 2015 Breeders’ Cup winners hail from nine different Bruce Lowe numbered families, but only the ubiquitous No. 1 family, founded by Tregonwell’s Natural Barb mare 30 or so generations ago, provided more than two. Those four winners – Liam’s Map, Stephanie’s Kitten, Found, and Tepin – stem from disparate, more modern branches of the No. 1 family. The most recent common ancestor along the female line for those four winners is Prunella, by Highflyer, a foal of 1788, who is the 22nd dam of Liam’s Map, 21st dam of Stephanie’s Kitten, 18th dam of Found, and 21st dam of Tepin.