What kind of sources does Charles Mann use in 1491?

Charles Mann's 1491 uses a wealth of anthropological and archaeological work done in North and South America to prove that the indigenous people of the area had a history long before the first Europeans came and "discovered" America.  Mann cites events such as the discovery of Kennewick Man, a skull found in the Pacific Northwest which is older than the old theory of the Bering Land Bridge.  He points to fields in the Amazon which could not have been created by accident, but rather by natives acting on their environment in order to make it better suited for their survival.  Mann uses burial sites as evidence that strong trade networks existed in the Americas before Columbus--one example is a feather of a tropical bird being located as far north as Cahokia.  Mann's work in this field is part of a growing field of history that focuses on native history.