Calculating Starvation Risk
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Calculating Starvation Risk Andrew D Higginson Psychology, University of Exeter, Exeter, UK
(Wells 2009). Researchers have attempted to assess whether food shortage and the consequent risk of starving to death has provided sufficiently strong selective pressure to cause the high levels of obesity (Prentice et al. 2008; Speakman 2006).
Synonyms Mortality Risks and Rates Deaths from famine; Mortality rates; Thrifty genotype
Definition Inferring the probability of starving to death from historical data.
Introduction In prehistory and in historic times, humans have been at risk of such severe food shortage that they may starve to death. Such food shortages, largely in the form of long-term famines, may be due to natural conditions causing crop failure, economic or political policies, war, or combinations of these. This risk of famine is thought to have acted as a selective pressure on human physiology and cognition in determining the storage of food in the body, mainly energy in the form of fat. Various hypotheses including the thrifty genotype hypothesis explain humans’ susceptibility to becoming obese due to this selective pressure
Formally, “starvation” is the process of consuming insufficient calories to maintain body weight, rather than starving to death. However, for clarity herein “starvation” is intended to convey mortality due to insufficient calories over a sufficiently prolonged period. The risk of starvation can be most simply calculated as the probability of dying from starvation per person per year. More properly, this is called the rate of starvation, since a risk is something that might happen, whereas a rate is events per unit of time. The rate of starvation is used to assess the selective pressure for animals, including humans, to store fat. There has been debate about whether this pressure has been sufficiently large to cause obesity in contemporary populations (Prentice et al. 2008; Speakman 2006). The magnitude of a selective pressure relates not to the absolute magnitude (e.g., of mortality) but the variance in magnitude within a population. The extent to which the risk can be altered by mitigating adaptations is key. The risk of starvation is the rate that would be realized if there was
© Springer Nature Switzerland AG 2020 T. K. Shackelford, V. A. Weekes-Shackelford (eds.), Encyclopedia of Evolutionary Psychological Science, https://doi.org/10.1007/978-3-319-16999-6_2653-1
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no mitigation. Humans are clearly adapted to mitigate the risk of starvation: this is the main role of body fat. Logical argument shows that since there is mitigation, the starvation rate cannot be used to measure the starvation risk (McNamara and Houston 1987). Since not all people are as obese as physically possible, there is clearly some selective pressure that causes lower fat storage. Even obese people tend to defend a certain level of fat: rarely do people just carry on getting heavier indefinitely. Ecologists consider that animals are lean because the risk of being killed by a predator exerts a pressure (Houston et
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