... and I on the opposite shore will be,
ready ro ride and spread trhe alarm,
to every middlesex village and farm.
Right, 8th grade! I remember that! Sort of.
Actually, the major debate on the west coast is of an early coastal migration, independent from and probably earlier than the inland migration. This idea explains a lot, including the early Santa Rosa Island skeleton (13,400 years old), and possibly Kennewick and other early skeletal remains from that area.