The chasm between pedigrees of American dirt horses and the international mainstream of pedigrees of the rest of the world’s elite Thoroughbreds, which race mostly on turf, has widened in the last two decades. Although more than 95% of the world’s Thoroughbreds descend in male line from American-bred stallions, grass racing in the rest of the world has selected different descendants of Northern Dancer and Mr. Prospector that work better in their local environment than the strains that work here on dirt.