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Cited by 260Cultural Differences and ValuesEvolutionary Psychology and Human BehaviorCulture, Economy, and Development Studies

Parasites, democratization, and the liberalization of values across contemporary countries

Thornhill, Randy, Fincher, Corey L., Aran, Devaraj·2009·Biological Reviews
DOI 10.1111/j.1469-185x.2008.00062.x
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Abstract

The countries of the world vary in their position along the autocracy-democracy continuum of values. Traditionally, scholars explain this variation as based on resource distribution and disparity among nations. We provide a different framework for understanding the autocracy-democracy dimension and related value dimensions, one that is complementary (not alternative) to the research tradition, but more encompassing, involving both evolutionary (ultimate) and proximate causation of the values. We hypothesize that the variation in values pertaining to autocracy-democracy arises fundamentally out of human (Homo sapiens) species-typical psychological adaptation that manifests contingently, producing values and associated behaviours that functioned adaptively in human evolutionary history to cope with local levels of infectious diseases. We test this parasite hypothesis of democratization using publicly available data measuring democratization, collectivism-individualism, gender egalitarianism, property rights, sexual restrictiveness, and parasite prevalence across many countries of the world. Parasite prevalence across countries is based on a validated index of the severity of 22 important human diseases. We show that, as the hypothesis predicts, collectivism (hence, conservatism), autocracy, women's subordination relative to men's status, and women's sexual restrictiveness are values that positively covary, and that correspond with high prevalence of infectious disease. Apparently, the psychology of xenophobia and ethnocentrism links these values to avoidance and management of parasites. Also as predicted, we show that the antipoles of each of the above values--individualism (hence, liberalism), democracy, and women's rights, freedom and increased participation in casual sex--are a positively covarying set of values in countries with relatively low parasite stress. Beyond the cross-national support for the parasite hypothesis of democratization, it is consistent with the geographic location at high latitudes (and hence reduced parasite stress) of the early democratic transitions in Britain, France and the U.S.A. It, too, is consistent with the marked increase in the liberalization of social values in the West in the 1950s and 1960s (in part, the sexual revolution), regions that, a generation or two earlier, experienced dramatically reduced infectious diseases as a result of antibiotics, vaccinations, food- and water-safety practices, and increased sanitation. Moreover, we hypothesize that the generation and diffusion of innovations (in thought, action and technology) within and among regions, which is associated positively with democratization, is causally related to parasite stress. Finally, we hypothesize that past selection in the context of morbidity and mortality resulting from parasitic disease crafted many of the aspects of social psychology unique to humans.

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  • High xenophobia and ethnocentrism correspond to the Western value system referred to as conservatism, whereas low xenophobia (i.e., high xenophilia toward out-groups) and restricted ethnocentrism (i.e., focus on nuclear family) correspond to more liberal values.

    “High xenophobia and ethnocentrism correspond to the Western value system referred to as conservatism, whereas low xenophobia (i.e., high xenophilia toward out-groups) and restricted ethnocentrism (i.e., focus on nuclear family) correspond to more liberal values”

    From Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity (2012) · cites this paper as Thornhill et al. 2009

  • In-group assortative sociality is an example of adaptive phenotypic plasticity, that is, of a conditional strategy with multiple contingent tactics.

    “In-group assortative sociality is an example, we argue, of adaptive phenotypic plasticity, that is, of a conditional strategy with multiple contingent tactics”

    From Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity (2012) · cites this paper as Thornhill et al. 2009

  • The benefits of out-group interactions include gains through intergroup trade, new and better ideas and technology, and diversified and larger social networks for marriage and other social alliances.

    “The benefits of out-group interactions include gains through intergroup trade, new and better ideas and technology, and diversified and larger social networks for marriage and other social alliances”

    From Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity (2012) · cites this paper as Thornhill et al. 2009

  • The countries in which the demographic transition has occurred are the same ones that have experienced a relative emancipation from infectious disease.

    “Moreover, the countries in which the demographic transition has occurred are the same ones that have experienced a relative emancipation from infectious disease (Thornhill et al. 2009).”

    From Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity (2012) · cites this paper as Thornhill et al. 2009

  • The values that lead to democracies versus autocracies or wealth versus dearth appear to causally arise from different infectious diseases ecologies.

    “This is because the values that lead to democracies versus autocracies or wealth versus dearth appear to causally arise from different infectious diseases ecologies (Thornhill et al. 2009).”

    From Parasite-stress promotes in-group assortative sociality: The cases of strong family ties and heightened religiosity (2012) · cites this paper as Thornhill et al. 2009

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Authors
Thornhill, R., Fincher, C. L., & Aran, D.
Affiliations
University of New Mexico (US)
Corresponding author
Thornhill, Randy
ORCID
Fincher, Corey L.
Venue
Biological Reviews
Publisher
Wiley
Published
2009-01-30
Volume
84
Issue
1
Pages
113-131
ISSN
  • 0006-3231 (ISSN-L)
  • 1464-7931
  • 1469-185X
DOI
10.1111/j.1469-185x.2008.00062.x
OpenAlex
W1976018026
Cited by
260
References
129
Citations by year
2026: 3 · 2025: 4 · 2024: 11 · 2023: 8 · 2022: 18 · 2021: 33 · 2020: 34 · 2019: 8 · 2018: 9 · 2017: 9 · 2016: 11 · 2015: 19 · 2014: 31 · 2013: 12 · 2012: 17
FWCI
1.43
Type
journal article
Language
en
Open access
closed
Licence
onlinelibrary.wiley.com/termsAndConditions#vor (vor)
Locations
  • Biological reviews/Biological reviews of the Cambridge Philosophical Society (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Social Sciences › Psychology › Social Psychology › Cultural Differences and Values
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Evolutionary Psychology and Human Behavior
  • Social Sciences › Demography › Culture, Economy, and Development Studies
Keywords
democratization, infectious disease prevalence, individualism-collectivism, gender egalitarianism, xenophobia, ethnocentrism, property rights, parasite prevalence, evolutionary psychology, social values, diffusion of innovations, sexual revolution, cross-national comparison
MeSH terms
Animals, Communicable Diseases, Conservation of Natural Resources, Cross-Cultural Comparison, Biological Evolution, Female, Host-Parasite Interactions, Humans, Male, Parasites, Parasitic Diseases, Epidemiologic Factors, Sex Distribution

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