During the 19th and early 20th centuries, the picture of Tyrtaeus' life has been complicated by doubts about the authenticity of many of his verses, dated by various scholars to the 5th or 4th century BC. A theory that "Tyrtaeus" was in fact a 5th century Athenian was even posited by Eduard Schwartz in 1899. According to Gerber (1997), however, "that skepticism has now largely disappeared", and disagreements among scholars now essentially revolves around the version of fragment 4 that should be accepted as genuine (Plutarch's or Diodorus' version, or a combination of the two), and about the dating of fragment 12, which some critics have assigned to the time of Xenophanes (c. 570 – c. 475 BC) or shortly before 498 BC.