Is there bias in 1491 by Charles C. Mann?

Charles C. Mann's book 1491 is considered groundbreaking because he looks at American history from an indigenous point of view.  The book states that indigenous societies were older than already thought and that they were every bit as strong and diverse as contemporary societies in Africa and Europe. Many academics have praised Mann's work as adding to the historical conversation about Native American tribes, as most of the work done in this field has been based on the natives' relationship to the European.  

Mann's work does have some bias, however.  He discounts most of the work done over the last two hundred years by previous native historians as being biased towards Europeans and, in many cases, racist.  While this is a valid point in many cases, it would be a mistake to throw out all of the work done in this field over the last hundred years.  Also, Mann is not an anthropologist by trade, so his arguments would carry more weight if he included some work done by leading anthropologists.  Mann's 1491 is most valuable in that this is one of the first mainstream history books that looks at Native American achievements pre-Columbus; hopefully other books will find a way to combine earlier historical studies with Mann's.