%A Dr. Stefan Bracha %A Adam S. Bracha %A Dr. Andrew E. Williams %A Tyler C. Ralston %A Jennifer M. Matsukawa %J Clinical Autonomic Research %T The human fear-circuitry and fear-induced fainting in healthy individuals The paleolithic-threat hypothesis %X 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 %K fainting, human evolution, war, combat, fear-circuitry, androgens, stress-induced disorders %P 238-241 %V 15 %D 2005 %L cogprints5035