Akatena,
The entrance to the cave is very small and one has to enter it on one's knees.So the archaeologists called it "On Your Knees Cave".
Limited genetic data suggests that the ancient Ainu and Jomon could [?] have common ancestry.Suspect that both peoples came to America by the route that you suggested.The Ainu and Jomon have long maritime traditions and had water craft at an early stage of their prehistory.