According to archaeological evidence, however, these adaptation strategies were not always sufficient during times of climate-induced stress. Human remains showing the effects of malnutrition are fairly common, and conflict caused in part by climate-induced shortfalls in farming has left traces that include fortified sites, sites placed in defensible locations and trauma to human bone. Larger and more hierarchical groups emerged, first in Mesoamerica and then in the southwest and southeast USA as well as the Midwest USA. These groups offered the possibility of buffering poor production in one area with surplus from another, but they also tended to increase inequality within their borders and often attempted to expand at the expense of their neighbours, introducing new sources of potential conflict. Dense hierarchical societies also arose in other areas such as the northwest coast where agriculture was not practised but resources, such as salmon and roots, were abundant and either relatively constant or storable.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report