Horse sacrifice is the ritual killing and offering of a horse, usually as part of a religious or cultural ritual. Horse sacrifices were common throughout Eurasia with the domestication of the horse and continuing up until the spread of Abrahamic religions, or in some places like Mongolia, of Buddhism. The practice is rarely observed in some cultures even today. Many ethnic religions from Indo-European speaking peoples show evidence for horse sacrifice, and comparative mythology suggests that they derive from a purported Proto-Indo-European ritual and common root, though the practice is also observed among non-Indo-European speaking peoples, especially in nomadic societies from the Eurasian steppe. Horses are often sacrificed in a funerary context, and interred with the deceased, a practice called horse burial. There is evidence but no explicit myths from the three branches of Indo-Europeans of a major horse sacrifice ritual based on a speculated mythical union of Indo-European kingship and the horse. The Indian Aśvamedha is the clearest evidence preserved, but vestiges from Latin and Celtic traditions allow the reconstruction of a few common attributes. Some scholars, including Edgar Polomé, regard the reconstruction of a purported common Proto-Indo-European ritual as unjustified due to the difference between the attested traditions. The reconstructed myth involves the coupling of a king with a divine mare which produced the divine twins. A related myth is that of a hero magically twinned with a horse foaled at the time of his birth (for example Cuchulainn, Pryderi), suggested to be fundamentally the same myth as that of the divine twin horsemen by the mytheme of a "mare-suckled" hero from Greek and medieval Serbian evidence, or mythical horses with human traits (Xanthos), suggesting totemic identity of the hero or king with the horse. Ashvamedha was a political ritual that was focused on the king's right to rule. The horse had to be a stallion and it would be permitted to wander for a year, accompanied by people of the king.