The natives did a bunk
Malcolm Gaskill: The Little Ice Age, 19 July 2018
“... experienced climate change but that they may, in part, have caused it. The palaeoclimatologist William Ruddiman has suggested that people started assaulting the ozone layer with greenhouse gases about eight thousand years ago, when farming began to replace hunting and gathering. Deforestation carried out by a growing population may have made the world ... ”