Final answer:
Two unexpected details from Mann's description of pre-Colombian Native America in California are the sophisticated trade networks and the healthy diet and semi-sedentary lifestyle of hunter-gatherers, contradicting stereotypes of primitive living and challenging the narrative that agricultural advancements signify 'progress'.
Step-by-step explanation:
From the description provided by Mann, two unexpected details about pre-Colombian Native America, specifically in California, include the extent and sophistication of the native trade networks and the surprising fact that many Native Americans lived in semi-sedentary villages with a diet that could be considered better than that of agriculturalists. While commonly portrayed as simple hunter-gatherers, the diversity of the California region and the sophistication of its societies are often underestimated. It is surprising to learn of the complex economic systems and the participation in large trade networks that extended well beyond local boundaries, contradicting the notion that these communities were isolated and primitive.
In the passage, it is noted that the peoples of California were involved in vast trade networks, an aspect often not highlighted in discussions about pre-Colombian America. This level of economic complexity suggests a level of societal organization and reach that is not typically associated with the hunter-gatherer stereotype. Additionally, the idea that contrary to popular belief, a society's transition from hunting and gathering to agriculture is not necessarily a sign of 'progress' was surprising, as it challenges the standard narrative of human societal evolution.