The observations that led to this conclusion were Jumong's early death, the difference in surnames, Yuri's harsh behavior toward some of Jumong's most prized subjects, and the differences in the styles of rule. Jumong died at the age of 40, which is quite early compared to that of some of his successors and predecessors. Very few of the rulers of that time period died before the age of 40. The difference in surnames may signify dynastic change from the Go family to the Hae family.