August 24, 2005

The Neolithic and the evolution of fear

The following article argues that certain unexplained fear symptoms evolved during the Neolithic. Here is how the authors describe Neolithic warfare:
Paleo-anthropological research has documented a specific pattern of prehistoric inter-group warfare in the Neolithic. In contrast to warfare in historical times, Neolithic inter-group warfare almost exclusively involved attacks against non-combatants in unsuspecting settlements by raiding parties of mateless young, post-pubertal males in search of material and especially reproductive resources. Neolithic combat occurred exclusively between young males, with females and children serving as objects of competition. This has been clearly documented by research on prehistoric human remains. It has been estimated that the victors killed 15%–50% of post-pubertal males and most infants and toddlers, and took females and most weaned pre-pubertal individuals captive (Lambert, 1997, Larsen, 1999, LeBlanc and Register, 2003 and Maschner and Reedy-Maschner, 1998).

The authors argue that the higher prevalence of these unexplained fear symptoms in women than in men, and in younger persons is due to the special nature of Neolithic warfare. Before the Neolithic, humans were most in danger from non-human predators; a fear response played no role against such predators. However, during the Neolithic, other humans replaced non-humans as the greatest danger. Pseudo-neurological problems evolved as a way to signal to the attacking males that one was incapacitated and hence did not pose a danger. This strategy worked especially for young females who are desirable for their mating potential; pre-Neolithic non-human predators made no such distinctions, as humans of both genders and regardless of age were viewed as a food source.

Journal of Affective Disorders (Article in Press)

Evolution of the human fear-circuitry and acute sociogenic pseudoneurological symptoms: The Neolithic balanced-polymorphism hypothesis

H. Stefan Bracha et al.


In light of the increasing threat of large-scale massacres such as terrorism against non-combatants (civilians), more attention is warranted not only to posttraumatic stress disorder (PTSD) but also to acute sociogenic pseudoneurological (“conversion”) symptoms, especially epidemic sociogenic symptoms. We posit that conversion disorders are etiologically related to specific evolutionary pressures (inescapable threats to life) in the late stage of the human environment of evolutionary adaptedness (EEA). Bracha et al. have recently argued that from the neuroevolutionary perspective, medically unexplained efferent vasovagal syncope and medically unexplained craniofacial musculoskeletal pain in young otherwise healthy individuals, may be taxonomized as stress and fear-circuitry disorders. In the present article, we extend neuroevolutionary perspectives to acute pseudoneurological sociogenic (“conversive”) symptoms: psychogenic non-epileptic attacks (“pseudoseizures”), epidemic sociogenic disorders (DSM-IV-TR Epidemic “Hysteria”), conversive motor deficits (pseudo-paralysis and pseudo-cerebellar symptoms), and psychogenic blindness. We hypothesize that these perplexing pseudoneurological stress-triggered symptoms, which constitute psychopathology in extant humans, are traceable to allele-variant polymorphisms which spread during the Neolithic EEA. During Neolithic warfare, conversive symptoms may have increased the survival odds for some non-combatants by visually (i.e., “non-verbally”) signaling to predatory conspecifics that one does not present a danger. This is consistent with the age and sex pattern of conversive disorders. Testable and falsifiable predictions are presented; e.g., at the genome–transcriptome interface, one of the major oligogenic loci involved in conversive spectrum disorders may carry a developmentally sensitive allele in a stable polymorphism (balanced polymorphism) in which the gene expression mechanism is gradually suppressed by pleiotropic androgens especially dehydroxyepiandrosterone sulfate (DHEA-S). Taxonomic implications for the much-needed rapprochement between the forthcoming Diagnostic and Statistical Manual for Mental Disorders, Fifth Edition (DSM-V) and the International Classification of Diseases (ICD) are discussed.


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