Records of heads of state
Officially, the current Emperor of Japan, Akihito is the 125th in line from the first emperor Jimmu, who is variously believed to have reigned in the 1st or 7th century BC. The earliest documentary evidence is only for the 29th emperor, Kinmei (AD 509–571); however, this is sufficient such that even the most conservative of estimates still places the Japanese imperial family as among the oldest lines in the world today.
Emperor
As of the early 21st century, Japan's succession law prohibits a female from ascending the throne. With the birth of a daughter as the first child of the current crown prince, Naruhito, Japan considered abandoning that rule. However, shortly after the announcement that Princess Kiko was pregnant with her third child, the proposal to alter the Imperial Household Law was suspended by Prime Minister Junichiro Koizumi. On 3 January 2007, after the birth of her son, Prince Hisahito, Prime Minister Shinzo Abe announced that he would drop the proposal.