Persian dance refers to the dance styles indigenous to Iran. Genres of dance in Iran vary depending on the area, culture, and language of the local people, and can range from sophisticated reconstructions of refined court dances to energetic folk dances. The population of Iran includes many ethnicities, including numerous Iranian tribal and ethnic groups; Kurds, Azeri, Turkmen, Jews, Armenian, Georgian peoples, some of which can be found within the borders of modern-day Iran. Each group, region, and historical epoch has specific dance styles associated with it. Raghs (also spelled as Raqs) is the Arabic word for dance, and is almost exclusively the word used for dance in Persian, as the Persian word for dance, paykubi, is no longer in common usage. The Kurdish word for dance is Halperke, and the Lurs from Lorestan use the word Bākhten (or Bāzee) for dance. The earliest researched Persian dance is a dance worshiping Mithra (as in the Cult of Mithras) in which a bull was sacrificed. This cult later became highly adhered in the Roman Empire. This dance was to promote vigor in life. Ancient Persian dance was significantly researched by Greek historian from Herodotus of Halikarnassos, in his work Book IX (Calliope), in which he describes the history of Asian empires and Persian wars until 478 BC. Ancient Persia was occupied by foreign powers, first Greeks, then Arabs, and then Mongols and in turn political instability and civil wars occurred. Throughout these changes a slow disappearance of heritage dance traditions occurred. After the fall of Persian Empire, when the country was torn into pieces, Iranian and Afghan women and young girls were enslaved by the new conquerors, often forced into sexual slavery and required to perform erotic dance for new rulers. Religious prohibition of dancing in Iran came with the spread of Islam, but it was spurred by historical events. Religious prohibition to dancing waxed and waned over the years, but after the Iranian Revolution in 1979 dancing was no longer allowed due to its frequent mixing of the sexes. The Islamic Revolution of 1979, was the end of a successful era for dancing and the art of ballet in Iran. The Iranian national ballet company was dissolved and its members emigrated to different countries. According to the principles of the “cultural revolution” in Iran, dancing was considered to be perverse, a great sin, immoral and corrupting. As a result many of the talented Persian dancers moved to the West and spread out mainly in Europe and the United States and new generation of Iranian dancers and ballet artists have grown up in the Diaspora.