Original Article Infant and child death in the human environment of evolutionary adaptation Anthony A. Volk a, ⁎, Jeremy A. Atkinson b a Department of Child and Youth Studies, Brock University b Department of Psychology, State University of New York, Albany abstract article info Article history: Initial receipt 29 April 2011 Final revision received 21 November 2012 Keywords: Environment of evolutionary adaptedness Human evolution Infant mortality Child mortality The precise quantitative nature of the Environment of Evolutionary Adaptedness (EEA) is difficult to reconstruct. The EEA represents a multitude of different geographic and temporal environments, of which a large number often need to be surveyed in order to draw sound conclusions. We examine a large number of both hunter–gatherer (N = 20) and historical (N = 43) infant and child mortality rates to generate a reliable quantitative estimate of their levels in the EEA. Using data drawn from a wide range of geographic locations, cultures, and times, we estimate that approximately 27% of infants failed to survive their first year of life, while approximately 47.5% of children failed to survive to puberty across in the EEA. These rates represent a serious selective pressure faced by humanity that may be underappreciated by many evolutionary psychologists. Additionally, a cross-species comparison found that human child mortality rates are roughly equivalent to Old World monkeys, higher than orangutan or bonobo rates and potentially higher than those of chimpanzees and gorillas. These findings are briefly discussed in relation to life history theory and evolved adaptations designed to lower high childhood mortality. © 2013 Elsevier Inc. All rights reserved. 1. Introduction Evolution works in a forward direction, “solving” today's problems tomorrow (Dawkins, 1989). Bowlby (1982) coined the term Environ- ment of Evolutionary Adaptedness (EEA) to refer to the environment in which an organism's current genotypes have been selected for. The human EEA is not a single time, place, or culture but rather a summation of all of the ancestral environments in which human evolution has occurred (Foley, 1995). The EEA may or may not be similar for separate traits (Irons, 1998). Traditional theory suggests that, for many human traits, the EEA is based on a combination of environments that were present during, or immediately preceding to, the paleolithic period (Tooby & Cosmides, 1992; Miller & Kanazawa, 2007). However, it is important to note that recent theories suggest that the last 10,000 years have played a significant role as a source of evolutionary adaptations and are hence part of the human EEA (Cochran & Harpending, 2009; Hartl & Clark, 1997; Irons, 1998; Yi et al., 2010; Tishkoff et al., 2007). Combining the last 10,000 years with the paleolithic gives a large time frame in which we must investigate the selective pressures present in the human EEA. What do we know about the evolutionary pressures that were present in this combined human EEA? Detailed knowledge of the EEA is made difficult due to the paucity of evidence from our past. While we agree with others that this can be a serious limitation to the study of some aspects of the human EEA (Foley, 1995), we suggest that there are some areas in which the evidence for the EEA is quite robust. In particular, we believe that there is at least one aspect of the EEA that we can not only confidently describe qualitatively, but also be able to generate reliable quantitative estimates for infant and child mortality rates. 1.1. Infant and child mortality rates One universal in the history of childhood stands above all others. The history of childhood is a history of death (Volk & Atkinson, 2008; Volk, 2011). Before modernized civilizations, across all times and cultures, children faced grim odds of survival. We suggest that infant and child mortality might be one of the most enduring features of the human EEA. To study this aspect of the EEA we have chosen to use the two most commonly used demographic markers in the study of child mortality: infant mortality rate (IMR), which is the likelihood of dying prior to age 1, and child mortality rate (CMR), which is the cumulative probability of dying prior to approximate sexual maturity at age 15. Life history models of human selective pressures over the course of the lifespan suggest that infant and child mortality may represent the period of human life subject to the strongest forces of evolutionary selection (Jones, 2009). Small changes in infant and child mortality rates can have dramatic consequences for both individual life histories and broader demographic trends (Bogin, 1997; Jones, 2009; Stearns, 2006; Wood, 1994). Therefore there is a strong theoretical incentive from life history theory to determine the likely values of IMR and CMR in the human EEA. Evolution and Human Behavior 34 (2013) 182–192 ⁎ Corresponding author. Department of Child and Youth Studies, Brock University, St. Catharines, Ontario, Canada L2S 3A1. Tel.: +1-905-6885550x5368; fax: +1-905- 6412509. E-mail address: tvolk@brocku.ca (A.A. Volk). 1090-5138/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.evolhumbehav.2012.11.007 Contents lists available at SciVerse ScienceDirect Evolution and Human Behavior journal homepage: www.ehbonline.org