Norwegian historians Rudolf Keyser and Peter Andreas Munch held the traditional dating to the late 800s. The same applies to the historian Gustav Storm and the Icelandic philologist Finnur Jonsson. Around the time of World War I, saga literature was subjected to much criticism as a historical source, in Sweden by the brothers Lauritz and Curt Weibull, and in Norway by Halvdan Koht and Edvard Bull. In 1908, German philologist Gustav Neckel said Ynglingatal had to be a construction from the 1100s; Norwegian historian Claus Krag also said this in his book Ynglingatal and Yngling Saga. A study of historical sources, and joins Neckel's hypothesis. The late hypothesis Claus Krag claimed in 1990 that Ynglingatal origin should be dated to the 1100s and that it was based on other royal lists. In a research project during the 1980s Krag's attempt to justify the doubt regarding Ynglingatal age began to take shape, disregarding the traditional, uncritical acceptance. Krag studied the Yngling tradition's place in folklore and the Yngling's genealogy in relation to other European royal genealogies and scholarly genealogical works in Iceland. As an argument, Krag proposed that the first four kings' deaths represent the cosmology of Greek philosopher Empedocles, with the four classical elements Earth, Water, Air, and Fire, and thus that a euhemeristic vision influenced the description of the first few generations. Krag's hypothesis has received serious criticism on several points, and so far "a convincing case has not been made against the authenticity of the poem as a ninth-century creation". The early dating Krag's late dating has been challenged. If the saga is a late work of propaganda, it should reasonably have been concluded with Norwegian king Harald Fairhair and not by his largely unknown cousin Ragnvald Heidrumhære, whose meaning seems otherwise to have been lost after 1000. There are places and names in the poem that archeology has shown to have had great importance until the Viking Age, but not later, and thus should not have been stated in a more recent saga. Archeologist Dagfinn Skre is an advocate for these arguments. According to Swedish researcher Olof Sundquist, Krag bypasses clear signs of Ynglingatal on a tradition of Swedish area visible in kenning, place names and personal names. Cultural phenomena such as a king who goes to holy places and the memory of a warrior elite can point to ancient human migrations. Sundquist posits the theory that