I have the anthology Hunter-Gatherers: An Interdisciplinary Perspective on my desk because I'm doing a project on native diets.
Peoples of the far north, while interesting, aren't terribly relevant to debates about humanity's evolution because, in the scale of human evolutionary history, they haven't been there very long. They prove it's possible to survive on a diet of 90-98% meat, but that doesn't mean it's optimal. Unlike most hunter-gatherers, Eskimos have a high incidence of Osteoporosis.
However, Eskimos who are still following their traditional diet are still a lot healthier than most Americans. Unfortunately, most have now adopted a Westernized diet, which has led to high rates of obesity and diabetes.
It's theorized that the high rates of osteoporosis are caused by eating excessive amount of protein. Most illnesses in Eskimo populations, like diabetes, seem to be the result of civilization, but in this case, even pre-contact skeletons seem to be marred.
That said, skeletons from other societies that ate a diet high in both plant and animal foods are often remarkably healthy. This leads me to wonder if the real problem is the lack of plant foods, rather than the amount of protein.
From Kiple's A Moveable Feast:
...the healthiest ancient skeletal population turned up so far in a study of health and nutrition in the western hemisphere represents individuals living on Brazil’s south coast from about 1000 BCE to 1000 AD. Like so many of their North American counterparts, they enjoyed this good health because they remained hunter-gatherers –actually fishermen and shell fishers – who produced highly visible mounds while consuming a varied and protein-rich diet.
Another good example are the Ache of Paraguay. They eat an impressive amount of animal foods, but also rely on hundreds of plants.