 Genetic studies to date have been inconclusive about the closest relative of the Sorraia . On one hand , studies using mitochondrial DNA showed a relationship with the Przewalski 's Horse , in that Przewalski 's Horse has a unique haplotype ( A2 ) not found in domestic horses , which differs by just one single nucleotide from one of the major Sorraia haplotypes ( JSO41 , later A7 ) . In comparison , genetic distances within the domestic horse are as large as 11 nucleotide differences . However , this relationship with the Przewalski 's Horse was contradicted in another study using microsatellite data that showed that the genetic distance between the Prewalski 's Horse and the Sorraia was the largest . Such conflicting results can arise when a population passes through a genetic bottleneck , and evidence suggests that the Sorraia , among other rare breeds , has recently passed through a bottleneck , effectively obscuring the position of this breed in the family tree of the domestic horse . Thus , the morphological , physiological , and cultural characteristics of the Sorraia are the subject of continued study to better understand the relationship between various Iberian horse breeds and wild horse subspecies . 
