Here a difficulty occurs.  Mythologists, as a rule, are averse to the method of folklore.  They think it scientific to compare only the myths of races which speak languages of the same family, and of races which have, in historic times, been actually in proved contact with each other.  Thus, most mythologists hold it correct to compare Greek, Slavonic, Celtic, and Indian stories, because Greeks, Slavs, Celts, and Hindoos all speak languages of the same family.  Again, they hold it correct to compare Chaldaean and Greek myths, because the Greeks and the Chaldaeans were brought into contact through the Phoenicians, and by other intermediaries, such as the Hittites.  But the same mythologists will vow that it is unscientific to compare a Maori or a Hottentot or an Eskimo myth with an Aryan story, because Maoris and Eskimo and Hottentots do not speak languages akin to that of Greece, nor can we show that the ancestors of Greeks, Maoris, Hottentots, and Eskimo were ever in contact with each other in historical times.

Now the peculiarity of the method of folklore is that it will venture to compare (with due caution and due examination of evidence) the myths of the most widely severed races.  Holding that myth is a product of the early human fancy, working on the most rudimentary knowledge of the outer world, the student of folklore thinks that differences of race do not much affect the early mythopoeic faculty.  He will not be surprised if Greeks and Australian blacks are in the same tale.

In each case, he holds, all the circumstances of the case must be examined and considered.  For instance, when the Australians tell a myth about the Pleiades very like the Greek myth of the Pleiades, we must ask a number of questions.  Is the Australian version authentic?  Can the people who told it have heard it from a European?  If these questions are answered so as to make it apparent that the Australian Pleiad myth is of genuine native origin, we need not fly to the conclusion that the Australians are a lost and forlorn branch of the Aryan race.  Two other hypotheses present themselves.  First, the human species is of unknown antiquity.  In the moderate allowance of 250,000 years, there is time for stories to have wandered all round the world, as the Aggry beads of Ashanti have probably crossed the continent from Egypt, as the Asiatic jade (if Asiatic it be) has arrived in Swiss lake-dwellings, as an African trade-cowry is said to have been found in a Cornish barrow, as an Indian Ocean shell has been discovered in a prehistoric bone-cave in Poland.  This slow filtration of tales is not absolutely out of the question.  Two causes would especially help to transmit myths.  The first is slavery and slave-stealing, the second is the habit of capturing brides from alien stocks, and the law which forbids marriage with a woman of a man’s own family.  Slaves and captured brides would bring their native legends among alien peoples.