Clinical Autonomic Research

, Volume 15, Issue 3, pp 238–241 | Cite as

The human fear-circuitry and fear-induced fainting in healthy individuals

The paleolithic-threat hypothesis
  • H. Stefan BrachaEmail author
  • Adam S. Bracha
  • Andrew E. Williams
  • Tyler C. Ralston
  • Jennifer M. Matsukawa


The Paleolithic-Threat hypothesis reviewed here posits that habitual efferent fainting can be traced back to fear-induced allelic polymorphisms that were selected into some genomes of anatomically, mitochondrially, and neurally modern humans (Homo sapiens sapiens) in the Mid-Paleolithic because of the survival advantage they conferred during periods of inescapable threat. We posit that during Mid-Paleolithic warfare an encounter with “a stranger holding a sharp object” was consistently associated with threat to life. A heritable hardwired or firm-wired (prepotentiated) predisposition to abruptly increase vagal tone and collapse flaccidly rather than freeze or attempt to flee or fight in response to an approaching sharp object, a minor injury, or the sight of blood, may have evolved as an alternative stress-induced fear-circuitry response. Such a stable (balanced) polymorphism for the hemodynamically “paradoxical” flaccid-immobility in response to these stimuli may have increased some non-combatants’ chances of survival. This is consistent with the unusual age and sex pattern of fear-induced fainting. The Paleolithic-Threat hypothesis also predicts a link to various hypo-androgenic states (e. g. low dehydroxy-epiandrosterone-sulfate. We offer five predictions testable via epidemiological, clinical, and ethological/ primatological methods. The Paleolithic-Threat hypothesis has implications for research in the aftermath of man-made disasters, such as terrorism against civilians, a traumatic event in which this hypothesis predicts epidemics of fear-induced fainting.

Key words

fainting human evolution war combat fearcircuitry androgens stress-induced disorders 


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Copyright information

© Steinkopff Verlag 2005

Authors and Affiliations

  • H. Stefan Bracha
    • 1
    Email author
  • Adam S. Bracha
    • 2
  • Andrew E. Williams
    • 3
  • Tyler C. Ralston
    • 1
  • Jennifer M. Matsukawa
    • 1
  1. 1.National Center for Posttraumatic Stress Disorder, Dept. of Veterans AffairsPacific Islands Health Care System, Spark M. Matsunaga Medical CenterHonolulu (HI) 96813-2830USA
  2. 2.Cornell UniversityIthaca (NY)USA
  3. 3.Dept. of PsychologyUniversity of Hawaii at ManoaHonolulu (HI)USA

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