I saw this the other day! Man, talk about re-writing our knowledge.
It seems likely there were multiple migrations to the new world, and even possible that people came over and died.
Also - re mound building - there are several known mound sites in North America. There were huge cities in North America at one point pre-Colombus. The perception that Native Americans were primitive and uncivilized is a myth. They even had buffalo meat processing systems that would rival industrial scales. And there are soooo many more sites to discover and learn more.
