Incredibly variable, much like the rest of the world. Before European conquest, there were vast differences between natives throughout the Americas. There were many solidified empires: The Inca, who engineered massive roadways designed for travel so that tribute tribes could send labor drafts to the Inca ruler as well as send tributes (they had a massive tributary system which worked under the "Vertical World") to the rulers. The Inca had a vast agrarian economy and a huge diet diversity creating longer life spans. Besides agrarian societies there are also the Plains Indians: The Sioux (to anyone but the Sioux themselves, Sioux meaning enemy. The "Sioux" refered to themselves as Lakota, meaning "the people"), which were divided into many groups mainly leaded by the Brule, for the most part these tribes simply followed the buffalo herds. Because of a nomadic lifestyle, emphasizing combat and defense of one's society, many boys had a short lifespan and women were the majority of those in the villages. For instance, Sitting Bull was raised by his uncles, Four Horns and Looks-for-him-in-a-tent, which was a common practice. There are many mentions of these uncles having at least three sons each but by the time Sitting Bull is 10, the age where boys had learned to expertly ride and time horses, as well as hunt animals, there are no mentions of or accounts of these sons. Considering that Sitting Bull's father and uncles were all chiefs in some way it's easy to see that many men of the nomadic tribes had short lifespans or died young.