Running head: INFANT AND CHILD MORTALITY RATE IN THE HUMAN EEA
Haley McCormick, Joey Hoy and Kira Rohrer
Panel Presentation: Infant and Child Death in the Human Environment of Evolutionary
Adaptation
Loyola Marymount University
Evolutionary Psychology
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INFANT AND CHILD MORTALITY RATE IN THE HUMAN EEA
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Summary of :
Atikinson, J.A. & Volk, A.A. (2013). Infant and Child Death in the Human Environment of
Evolutionary Adaptation. Evolution and Human Behavior Research, 34, 182-192.
The present article aims to show how infant mortality rates (IMR) and child mortality rates
(CMR) played a significant role in establishing the environment of evolutionary adaptedness
(EEA). To better understand the EEA it is best to look at it in terms of a culmination of the
environments across human evolutionary history instead of one single environment. These
environments include the time during and immediately preceding the Paleolithic period. It is
important to note that the past 10,000 years have also played a crucial role in evolution and are
therefore also a part of the human EEA. The article presents data that displays drastic changes in
IMR and CMR across thousands of years and over numerous geographic locations in the human
EEA. The authors use this as a basis to assert that CMR and IMR are arguably the strongest
forces in evolutionary selection.
The authors define IMR as the likelihood of a human dying before the age of one and CMR
as the likelihood of a human dying before sexual maturation which was averaged at age 15. The
researchers compiled and examined data from three different human populations that would have
represented the EEA across human evolutionary history: hunter-gatherer data, human historical
data, and human agriculturalist data. Although it is impossible to travel back thousands of years
to observe these certain groups, the researchers observed modern tribes that are comparable to
our human ancestors that lived thousands of years ago. In a sense, it is a modern looking glass
into the past.
The researchers examined 18 modern hunter-gatherer tribes across various geographic
locations. These tribes were not influenced by external contact with the modern world. The
researchers found that despite the differences in cultures, geographic locations, and historical
time frames, the IMR and CMR of the tribes were significantly higher compared to modern
mortality rates. The mean IMR was 26.8% while the mean CMR was a staggering 48.8%. This
means that a little over half of the children in hunter-gatherer societies lived to the reproductive
age of fifteen.
Human historical data does not show much of a difference in child and infant mortality
rates. The researchers define human historical data as the last 10,000 years of human
evolutionary history. The researchers believe that historical data may represent a continuation of
the human EEA in terms of new adaptations that could alter infant and child survival. The
authors do point out that historical data may be skewed due to children’s smaller physical
remains, lack of death records, and low frequency of elaborate infant burials. Despite this
potential setback, the average mortality rates across 43 historical cultures remain quite high. The
average IMR was 26.9% while the mean CMR was 46.2%. Although slightly lower than huntergatherer tribes, the historical human data is significantly higher than the IMR and CMR of
modern times.
The third group the researchers observed was agriculturalists tribes. This group had the
lowest IMR and CMR of the three groups that were studied. Although much higher than modern
mortality rates, the mean IMR for agriculturalists was 20.6% while the CMR was 37.6%. While
some agriculturalist groups were similar to hunter-gatherer rates, most of them were not. The
researchers hypothesize that the lower mortality rates for the agriculturalists were due to
exposure to modernized Western laws, education, sanitation, food, and medicines. The
INFANT AND CHILD MORTALITY RATE IN THE HUMAN EEA
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researchers state that this is typical when humans made the transition from hunter-gatherer to
horticulturalists. However, since this data is likely to be skewed by modern, external influences,
the results for this group should be seen as merely speculative.
The researchers also examined a fourth group of nonhuman primate data. They aimed to
discover if other primate species faced the same selective pressures in their EEA as humans did
with IMR and CMR. Through compiling the data of different primate groups, the researchers
found that the pattern of human infant mortality was similar to that of Neanderthals, chimps, and
gorillas, but not to orangutans or bonobos, which was lower, and other primates, which was
higher. The researchers found a rough relationship between IMR of humans and species that are
most similar to humans genetically. This claim is to be used cautiously because apes face
different causes of infant mortality such as predation from other animals, a factor that did not
affect humans.
Near the end of the article, the researchers identify the main causes of infant and child
mortality across the EEA. The researchers start off by stating that it is difficult to determine the
cause of death even in modern circumstances, so they are left with only educated estimates from
the populations that they examined.
The researchers have laid substantial evidence for the strength of IMR and CMR in
evolutionary selection within the human EEA. Given the data, it was necessary for our ancestors
to overcome the significant IMR and CMR in order to reach reproductive age and adulthood. The
researchers point out that it would not matter if an individual had the potential to be a talented,
genetically fit, human being if that person did not survive past infancy and childhood to do so.
This point is central to the argument that infant and child mortality are one of the most important
selective pressures faced by humans in the EEA.
This article has produced data from archaeological, anthropological, historical, and
primate data. Through this, they were able to concur that the human EEA, IMR, and CMR have
congruence. Humans have has higher infant and child mortality rates, higher than other great
apes. However, the findings are congruent with Neanderthals, gorillas, and chimpanzees. Thus,
leading the researchers to believe that there is a possible phylogenetic influence on mortality
rates. The findings also suggested that humans had lower levels of predation when compared to
the other apes, showing that a main cause of IMR and CMR would be disease and infanticide;
allowing this to be a greater evolutionary pressure. The researchers further wanted to stress that
the main causes for mortality have much less concrete evidence.
Some evolutionary psychologists such as John Bowlby, who primarily founded the term
EEA, have been influences to this article. The researchers talk about evolutionary psychologists
that have suggested alloparenting and attentive parental care as a crucial feature that helped
children and infants stay alive. The article further states that males who are willing to
cooperative with other males regarding paternity issues are less likely to commit infanticide. The
authors of the article also posed a point that childhood and infancy may be in fact adaptations of
their own. These children are adapted to meet the needs of childhood and reduce the chance of
dying on their own. Crying, facial cues, and possible aggression to obtain food are possible
adaptations the children have to survive.
At the end of this article, the researchers emphasize that this paper is used to serve as a
estimate of how important the pressure of the EEA is and further, how infant and child mortality
may have played a very crucial role in the shaping of the human mind itself. The researchers
stress their hope in that someone may use their information and data to further the research on
this subject and use their numerical values with confidence.