the main idea is the out of africa hypothesis: it says that humans developed on the african continent, and spread from there. another important site is called kow swamp, in the northern part of victoria. it consists of about twenty skeletons, which are between 5,000 and 10,000 years old. the morphology of mungo man is noticeably different from these skeletons. for this reason, some researchers have said that australia was probably settled twice. the settlers were probably descendants of homo erectus and came from the asian mainland. this theory is based on the analysis of mitochondrial dna. if this is true, the two lines, that of mungo man and that of modern humans, separated a long time ago. this would also mean that mitochondrial eve of this line and that of modern humans would be older than mitochondrial eve of all living humans.