People of the owl : a novel of prehistoric North America / Kathleen O'Neal Gear and W. Michael Gear.

Enhanced descriptions from Syndetics:

Four thousand years ago a boy is thrust into manhood long before he's ready. Young Salamander would much rather catch crickets than dabble in the politics of his clan. But when his heroic brother is killed, Salamander becomes the leader of America's first city. He inherits his brother's two wives, who despise him, and is forced to marry his mortal enemy's daughter to forge an alliance for the trade goods his people desperately need. But he's only fifteen winters old! Technically he's not even a man, and most people consider him to be the village idiot! Worse, each of his wives has secretly been ordered by her clan to kill him.Cast adrift in a stark wilderness of political intrigue where assassins are everywhere, young Salamander has no choice but to become a man-and quickly. For his own greatest enemies are closing in, intent upon destroying him and his clan and taking over Sun Town for themselves.