If anything, the film underplays the scale and importance of the discovery. Mierendorf has spent better than two decades championing the archaeology of the high country. For a long time archaeologists had written off the pre-contact history of the North Cascades highlands, arguing in part that the rich environment of the coastal lowlands meant that Indians seldom ventured far into the mountains. The theory gained strength from confirmation bias--because scientists knew that Indians did not use the mountains they did not look for signs of habitation there, and because they had not found signs of human habitation (that they had not looked for) they knew the areas were uninhabited. Many fields suffer from similar received wisdom.
Tramping around the North Cascades, Mierendorf quickly realized there were extensive signs of pre-contact human utilization, and began gathering evidence. This article from the magazine of Washington State University tells some of the story. Or you can hear the man in his own words in a podcast on this page.
I knew Bob a bit back in the day, when I cleared trails and cleaned campgrounds for North Cascades National Park, and it is good to see the things that he was telling us over campfires 20 years ago coming out in print and becoming the new narrative of native peoples in the North Cascades. Congratulations Bob!