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Climate change is an indisputable threat to human health, especially for societies already confronted with rising social inequality, political and economic uncertainty, and a cascade of concurrent environmental challenges. Archaeological data about past climate and environment provide an important source of evidence about the potential challenges humans face and the long-term outcomes of alternative short-term adaptive strategies. Evidence from well-dated archaeological human skeletons and mummified remains speaks directly to patterns of human health over time through changing circumstances. Here, we describe variation in human epidemiological patterns in the context of past rapid climate change (RCC) events and other periods of past environmental change. Case studies confirm that human communities responded to environmental changes in diverse ways depending on historical, sociocultural, and biological contingencies. Certain factors, such as social inequality and disproportionate access to resources in large, complex societies may influence the probability of major sociopolitical disruptions and reorganizations—commonly known as “collapse.” This survey of Holocene human–environmental relations demonstrates how flexibility, variation, and maintenance of Indigenous knowledge can be mitigating factors in the face of environmental challenges. Although contemporary climate change is more rapid and of greater magnitude than the RCC events and other environmental changes we discuss here, these lessons from the past provide clarity about potential priorities for equitable, sustainable development and the constraints of modernity we must address.

Long-distance exchange of copper objects during the Archaic Period (ca. 8000-3000 cal B.P.) is a bellwether of emergent social complexity in the Eastern Woodlands. Originating from the Great Lakes, the Canadian Maritimes, and the Appalachian Mountains, Archaic-age copper is found in significant amounts as far south as Tennessee and in isolated pockets at major trade centers in Louisiana but is absent from most of the southeastern United States. Here we report the discovery of a copper band found with the cremated remains of at least seven individuals buried in the direct center of a Late Archaic shell ring located in coastal Georgia. Late Archaic shell rings are massive circular middens thought to be constructed, in part, during large-scale ritual gatherings and feasting events. The exotic copper and cremated remains are unique in coastal South Carolina and Georgia where Archaic-age cremations are conspicuously absent and no other Archaic copper objects have been reported. Elemental data produced through laser ablation inductively coupled plasma mass spectrometry shows the copper originated from the Great Lakes, effectively extending Archaic copper exchange almost 1,000 km beyond its traditional boundaries. Similarities in mortuary practices and the presence of copper originating from the Great Lakes reveal the presence of long-distance exchange relations spanning vast portions of the eastern United States and suggest an unexpected level of societal complexity at shell ring localities. These findings are consistent with the hypothesis that elite actors solidified their positions through ritual gatherings and the long-distance exchange of exotic objects during the Archaic.

Since the publication of Charles Darwin's The Descent of Man and Selection in Relation to Sex in 1871 (1), there has been a vigorous debate about the meaning of sexual dimorphism for a range of physical attributes in numerous animal species, including primates and humans, extinct and extant. Key points of discussion are how to interpret size dimorphism in past humans and human-like ancestors and what inferences can be drawn about the evolution of human mating systems and social organization. In this issue of PNAS, Reno et al. (2) report on their investigation of sexual dimorphism in the three-million-year-old Australopithecus afarensis , an important and well known hominid, ancestral to the genus Homo (3). Insight into dimorphism in this taxon has important implications for social behavior and organization in later and present-day humans. Body mass dimorphism varies dramatically among primate species, both present and past. For most anthropoids, males are bigger than females (4–8). Humans today display relatively limited sexual dimorphism (≈15%), whereas some of the other hominoids (gorillas and orangutans) are highly dimorphic (>50%) (5, 9). Body mass is easily determined in living species. For past nonhuman primates and human ancestors, mostly represented by fragmentary fossil remains, body mass is far less accessible. Recently, the femur head (the ball of bone at the top of the femur that fits into the hip joint) has been invoked as a source for estimating body mass in early hominids, Homo , and its evolutionary predecessor, Australopithecus (10, 11). Comparisons of body mass in fossil hominids reveal that general levels …