Analysis of ancient human DNA and primer contamination: one step backward one step forward

The analysis of DNA from archaeological human remains is plagued by a unique set of methodological problems concerning contamination with modern exogenous DNA. Through an original approach, we propose complementary methods to identify all potential sources of contamination and complete guidelines for the validation of ancient human sequences. The study presented was conducted on non-European human samples (Polynesian and Amerindian) which were collected with all precautions during excavation. This permitted us to distinguish without ambiguity authentic and contaminant sequences. The samples' origins and histories were perfectly known, allowing us to trace all potential contamination sources and to determine the efficiency of precautions followed during all steps of the study. The data obtained confirm that precautions taken during sampling effectively prevent contamination. However, we demonstrate that human contamination can also be introduced during genetic analyses even if all precautions are strictly followed. Indeed, numerous human contaminations were detected in template-PCR products and negative controls, resulting in a striking diversity of contaminant mitochondrial DNA sequences. We argue that this contamination partly derives from the primers. To our knowledge, no previous experiment has been performed to investigate primers as a possible source of human contamination despite the fact that this specific type of contamination poses a real problem in terms of validating ancient human DNA studies. Finally, we confirm that the detection of contaminants in negative controls is clearly related to the number of PCR cycles used. This study enhances our understanding of contamination processes and confirms that, in reality, an absolutely contamination-free situation cannot be obtained. As a consequence, we propose improvements to the guidelines usually followed in the field in order to take the highly probable contamination of PCR reagents, including primers, into account.     

Triggers for alcohol‐related violence in young male offenders

Purpose. Improving the effectiveness of offender treatment programmes is important and one approach is to attend to their content. The aim here was to identify triggers to alcohol‐related violence to inform the development of programmes to treat this problem. Method. Information from 149 young male offenders’ accounts of incidents of alcohol‐related violence was studied using thematic analysis. Results. Sixteen triggers for violence were identified and these were organized into six themes: (1) being offended by someone, (2) seeing an opportunity for material gain, (3) seeing others in need of help, (4) perception of threat, (5) distress, and (6) wanting a fight. Discussion. The implications of the results for developing treatments for alcohol‐related violence are presented. First, identifying triggers should be part of the treatment programme and ways of avoiding triggers should be addressed. Second, changing values, specifically hypermasculine and antisocial values, could attenuate the rewards signalled by the triggers. Third, methods of reducing the potency of triggers would be of value and would include addressing issues of need for respect and responses to perceived disrespect. Fourth, non‐violent ways of helping people who are in trouble need to be introduced. Fifth, coping with threat cues through distraction and increasing self‐awareness would reduce the effects of ‘alcohol myopia’. Sixth, seeking fights for excitement could be reduced by examining the costs through motivational procedures. Finally, and self‐evidently, a primary target of treatment programmes to reduce alcohol‐related violence should be to reduce the level and frequency of alcohol intoxication.     

La guerre vue d'Ochollo (Éthiopie méridionale)

La quête pour la reconnaissance de la subjectivité et la dignité est au coeur des mouvements sociaux actuels. Les Africains se battent pour obtenir la reconnaissance depuis l’époque où la traite des esclaves et plus tard la colonisation les ont dépouillés de leurs qualités humaines. Ces combats ont été essentiellement révélés par l’écriture et le monothéisme. L’article actuel suggère aux lecteurs de considérer la construction performative du moi où la subjectivité Africaine / Noire est représentée dans toute son autonomie. L’exemple empirique proposé est celui de l’Afrique centrale.