Origins and initial settlement: the problem of origins , alliance theory of marriage. How close can we marry and how far away can we marry and derive certain benefits. Marry too far away, poor for alliance approach, Marry close distances key, groups that can mutually benefit: multiple vs single origins, point(s) of entry and spread, population sources, times and dates, aboriginal conceptions. Always suggest that they did not come from anywhere other than north america. Beringia and concept of refugium : concept of interstadial , advance and retreat of ice during wisconsin stage of pleistocene. Dependent on opening and closing of ice sheet, passage way. Long stretch of land, useful for people and animals. Interstadial: a long period, warming between cooler ice periods. * see chart in textbook, and map with ice straights identified. Cooler more opportunity to move across bridge region. When warming, water level rises and blocks movements.