Send us Fan MailIn this episode (part one of a two-part series), we trace the first ten thousand years of human life along the Mississippi Valley: who came here, what they built, and what we think they believed about the world they were living in.We start with ice. Glacial Lake Agassiz breaks its bank, Glacial River Warren tears a valley through Minnesota, and a waterfall the size of Niagara begins a slow retreat upriver to the spot we now call St. Anthony Falls. The first Minnesotans arrive to a landscape still reawakening, sharing it with mammoths and mastodons and this massive river. From there we follow people down the length of the valley as they learn to live off big rivers and floodplains, domesticate their first plants, and build monuments out of soil. At Watson Brake in Louisiana, hunter-gatherers raised eleven mounds a thousand years before the first Egyptian pyramid. At Poverty Point, thousands of people assembled a massive earthwork in about ninety days — apparently without a ruler telling them to. We also look up. The three-tiered cosmos of Upper World, Below World, and This World; the Earth Diver stories; and the Path of Souls, the star road the dead traveled — and which Hopewell builders in Ohio aligned their roads and mounds to meet. In the next episode, we’ll go deep into Cahokia and the invasion led by Hernando de Soto.