See www.examiner.com for the full story 'Cahokia's woodhenges' – and this is the much advertised mound people of the Ohio and Mississippi valleys that flourished in what was the Medieval Warm Period. The roots go back to the mid first millennium AD but what is emphasised here by this newspaper is an assumed astronomical link between a ring of post holes and stone circles. A stone circle was discovered in Alberta, far to the north in Canada, and is dated to around 3000BC – but the purpose of what are being called a series of woodhenge structures at Cahokia, is an unknown. However, there are actual antecedents for the Cahokia mounds and a particular style of architecture much further to the south, in what is now Georgia. Excavations at Kolomoki show that settlements in the region thrived during what was the Roman Warm Period, growing crops that had an origin in Mexico, such as corn. However, around 600AD the mounds and houses were abandoned and the people disappeared. It seems they moved northwards and there are traces of them along the Arkansas River and as far north as Illinois as well as the well known sites in the Ohio and Mississippi valleys. This may indicate a connection with the Mike Baillie low growth tree ring event at 536-45AD which appears to have affected the Old World to a similar degree (see David Key's Catastrophe: an investigation into the origins of the modern world). Drawings of the activities of native people in the early colonial period seems to suggest the post holes may have held totems with faces carved on them – possibly statues of ancestors or features of the gods.