In the annals of historical atrocities, few rival the slaughter of the indigenous population of the Americas. Recent research suggests that the 'Little Ice Age' was caused in part by the death of approximately ninety percent of the population of the Americas, a reduction of the population from about sixty million to about six million. With the human population plummeting and the subsequent reversion of farmland to forest, the theory goes, enough carbon dioxide was photosynthetically sequestered in the form of wood that it caused the Earth's temperature to drop.
Pre-Columbian North America was the home of sophisticated societies which built large communities, though racist hypotheses were promulgated to downplay the achievements of American autochthones- the large earthworks were attributed to Vikings, Atlanteans, a lost tribe of Israelites, giants... a whole slew of 'suspects'. In an egregious recent example, a pseudoscientific/pseudohistorical television series pushed the trope, by which I mean tripe, of giant mound builders, identified by at least one crank as half-Denisovan hybrid giants. With the paucity of Denisovan remains, these ancient people have become part of the legendarium of all sorts of 'WOO' peddlers, from Bigfoot aficianados to Nephilim nudniks. As if killing off the majority of Native Americans weren't bad enough, there are ongoing efforts to erase them from the historical narrative altogether.