Estate planning in the United States has evolved from English, European, and Middle Eastern traditions. During Biblical times, custom required people to leave property to their firstborn. Centuries later in Greek and Roman times, decedents could transfer property to other people. Estate planning remained mostly unwritten until the Middle Ages when Roman Emperor Justinian adopted a law requiring written wills. The requirement for written wills was perpetuated by English statutes adopted during the Post-Medieval Period. In modern times, written estate plans are still essential for individuals wanting to distribute property to family, friends, and others of their choosing.