Selective complexity and adaptive mortuary behavior.

T rends in human history are increased cultural complexity and social differentiation and marked beginnings, endings, reversals, and turns and twists at different scales (1). Within these trends, the creation of social groups and communities is an active process that involves cultural pluralism, ideology, negotiated identity, economy, the built environment, and mortuary expression. In most societies, death implies passage from a visible, living state to an invisible, buried one. This is not the case with the ancient Chinchorro society of the coastal Atacama Desert of north Chile and south Peru. In PNAS, the observations reported by Marquet et al. (2) on the mortuary practices of this society allow us to better understand the cultural processes and environmental conditions that connected human history, cognition, and ideology to reproduce small-scale maritime communities through repeated encounters with the artificially mummified cadavers of the dead. Organic matter such as the human body is naturally well preserved in the extremely arid environment of the desert. As presented by the authors (2), mummified remains were deliberately placed in shallow, visible graves with few offerings, and continuously removed and manipulated for interaction with the living. The Chinchorro society practiced two types of mummification: natural and artificial. Natural preservation involved burial in the ground, where the body was desiccated and preserved. Cadavers were artificially mummified and evidently socially distinguished by painting them red and black, coating them with mud, or bandaging and cording them with plant material. For practical purposes, natural desiccation was sufficed to preserve bodies: artificial treatment was preservation overkill. Marquet et al. (2) argue that the artificial treatment appeared in times of increased marine resources and fresh groundwater between approximately 7,500 and 4,500 y ago. This abundance led to a growth in the human population and thus the increase in the dead, as well as the appearance of new technologies, including mummification and tools for resource procurement. Throughout this period, visible burial sites built up across the coastal landscape, which led to more interactions between the living the dead. These increased encounters formed part of the cognitive map of people’s daily lives and played a central role in the making of the Chinchorro culture and the emergence of social complexity. One of the most studied topics in archaeology is the meaning of mortuary patterns. We know that burial remains are not incidental residues, but represent the direct and intentional consummation of conscious behavior. Many researchers have assumed that the social structure of a society is directly reflected by burial practices (3). That is, an individual’s treatment at biological death can be predictably related to the social identity that the individual had in life. An alternative view sees mortuary patterns related to ideology, symbolism, ritual, and history rather than just social organization (4). Not known by Marquet et al. (2) is the social, ideological, and symbolic meaning of the Chinchorro mummies. However, the authors are able to make the important distinction between biological death and social death (5, 6). The former is when the physical body ceases to function. The latter implies that the deceased stays alive as long as (s)he continues to interact socially and visibly with the living in societal events. In this regard, the biologically dead become socially active participants. The value of this unique mortuary approach is that it challenges our ideas about the nature of the relationship between the living and the dead and the physical manipulation of cadavers as shown by the complex preservation techniques of bodily decomposition, artificial reconstruction, and coating or sealing (7). As Arriaza (ref. 8, p. 30) has expressed: “Chinchorro mummification practices can be interpreted as a system to achieve continuity with life, rather than regeneration of life. . . In other words, in Chinchorro ideology, the dead became an extension of the living. . . That is, artificial mummification provided a resting place for the soul and therefore the mummies were considered living entities.” Further, painting and sealing the bodies suggest that the dead were given an identity and an aesthetic life-like quality. Although the ideological meaning of these practices is not clear, mummies seem to have been instrumental as socializing tools for the self-awareness and cognitive development of the living. As discussed by Marquet et al. (2), studies reveal that religious thoughts often derive from people’s cognitive capacities when they encounter certain phenomena such as dead bodies (9), which are objects of great attraction and curiosity in most societies. Does the information provided by Marquet et al. (2) tell us anything about Fig. 1. A basket fragment made of reeds and dyed in blue from the Huaca Prieta site on the north coast of Peru. The fragment represents a sophisticated basketry technology that coastal foragers and cultivators developed in the region between 7,500 and 4,500 y ago.