Throughout history, the Iberian breeds have been influenced by many different peoples and cultures who occupied Spain, including the Celts, the Carthaginians, the Romans, various Germanic tribes and the Arabs. The Iberian horse was identified as a talented war horse as early as 450 BCE.[5] Mitochondrial DNA studies of the modern Andalusian horse of the Iberian peninsula and Barb horse of North Africa present convincing evidence that both breeds crossed the Strait of Gibraltar and were used for breeding with each other, influencing one another's bloodlines.[19] Thus, the Andalusian may have been the first European "warmblood", a mixture of heavy European and lighter Oriental horses.[23] Some of the earliest written pedigrees in recorded European history were kept by Carthusian monks,[24] beginning in the 13th century. Because they could read and write, and were thus able to maintain careful records, monastics were given the responsibility for horse breeding by certain members of the nobility, particularly in Spain.[25] Andalusian stud farms for breeding were formed in the late 15th century in Carthusian monasteries in Jerez, Seville and Cazalla.[7]