Archaeological evidence plays a key role in longitudinal studies of humans and climate. Climate proxy data from Peruvian archaeological sites provide a case study through insight into the history of the “flavors” or varieties of El Niño (EN) events after ∼11 ka: eastern Pacific EN, La Niña, coastal EN (COA), and central Pacific or Modoki EN (CP). Archaeological proxies are important to the coastal Peruvian case because more commonly used paleoclimate proxies are unavailable or equivocal. Previously, multiproxy evidence from the Peruvian coast and elsewhere suggested that EN frequency varied over the Holocene: 1) present in the Early Holocene; 2) absent or very low frequency during the Middle Holocene (∼9 to 6 ka); 3) low after ∼6 ka; and 4) rapidly increasing frequency after 3 ka. Despite skepticism about the reliability of archaeological proxies, nonarchaeological proxies seemed to confirm this archaeological EN reconstruction. Although there is consensus that EN frequency varied over this period, some nonarchaeological and archaeological proxies call parts of this reconstruction into question. Here we review Holocene EN frequency reconstructions for the Peruvian coast, point to complexities introduced by apparent contradictions in a range of proxy records, consider the impact of CP and COA phenomena, and assess the merits of archaeological proxies in EN reconstructions. Reconciling Peruvian coastal paleoclimate data is critical for testing models of future EN behavior under climate variability.
Small-scale society furnishes the bread and butter of archeological research. Yet our understanding of what these communities did and how they achieved their purpose is still rudimentary. Using the ethnography of contact-era New Guinea, this paper presents a "social signaling" model of small-scale social systems that archeologists may find useful for contextualizing and interpreting the material record of these societies. It proposes that the organization of small-scale society was oriented, among other goals, towards biological and social reproduction, subsistence optimization, and military defense. To advance these multiple collective interests, however, these communities had to deal with three problems: an optimality problem, a conflictof-interest problem, and a free-rider problem. The optimality problem was solved with a modular (or segmented) social structure, the conflict-of-interest problem by a process of social signaling, and these two solutions together operated to resolve the free-rider problems they created. In addition to explaining the structure and function of small-scale societies, the model provides a unified framework that can account for the ceremonial behaviors, core cultural conceptions, and leadership forms that these societies generated.
Advances in primatological research have recently led to a hypothesis that lethal coalitionary raiding in chimpanzees is the product of an evolutionarily adaptive "dominance drive" that disposes adult males to seek out low-cost opportunities for conspecific killing. This conclusion has been extended into a claim that human warfare and other forms of coalitional killing are outcomes of a hardwired, "demonic male" complex. Reversing this evidential approach, I argue from data on conspecific killing in humans that humans and chimpanzees have an aversion to killing conspecifics. Their lethal violence, I propose, is more parsimoniously explained as the result of a developed intelligence capable of envisioning the future and, when necessary, of disabling this aversion to achieve desired goals.
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