title: The human fear-circuitry and fear-induced fainting in healthy individuals The paleolithic-threat hypothesis creator: Bracha, Dr. Stefan creator: Bracha, Adam S. creator: Williams, Dr. Andrew E. creator: Ralston, Tyler C. creator: Matsukawa, Jennifer M. subject: Evolution subject: Psychophysiology description: 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 hard- wired 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, 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 dehydroxyepiandrosterone-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 date: 2005 type: Journal (Paginated) type: PeerReviewed format: application/pdf identifier: http://cogprints.org/5035/1/2005_C.A.R_review_FEAR-CIRCUITRY-DRIVEN_FAINTS.pdf identifier: Bracha, Dr. Stefan and Bracha, Adam S. and Williams, Dr. Andrew E. and Ralston, Tyler C. and Matsukawa, Jennifer M. (2005) The human fear-circuitry and fear-induced fainting in healthy individuals The paleolithic-threat hypothesis. [Journal (Paginated)] relation: http://cogprints.org/5035/