Do you have a good link for the Seymour mounds? I Googled, but couldn't find much.
I know what you mean. I googled and only found Seymour Butts.
There seems to be a straight line heritage of Amerind pyramid architecture from Caral to Olmec sites like La Venta, Mexico; the Zapotec at Monte Alban; the predecessors of the Inca at Teotihuacan; the Maya, the Moche of Peru; and many others like the many later mounds and pyramids to be found along the course of the Mississippi River and tributaries.
Theres a site HERE that lists many more including the largest in the U.S. at Cahokia, IL, a huge one in Mississippi and others. The analogy between the Nile and its floods with Mississippi floods and replenishment of fertile topsoil is interesting. There doesnt appear to be any shortage of mounds, monumental constructions and pyramids in the Americas!
This is at the Northern edge of one of the Western Hemisphere's primary agricultural development areas ~ all the different kinds of Sunflower and Squash plants were domesticated here in ancient times by the earliest settled Indians ~ that's long before the Adena and Hopewell cultures, and about coincident with the Peruvians.
Squash are, of course, a subtropical plant so the original seeds were brought North to this area by Indians who lived far down on the Gulf Coast, or maybe even South America. Someone may have a date on the introduction of corn in this region, and that would be AFTER the arrival of what may have been a colony of Andean Indians.