families", whose effects contribute to several major societal problems, including later domestic violence and crime. Psychology The causes of violent behavior in people are often a topic of research in psychology. Neurobiologist Jan Vodka emphasizes that, for those purposes, "violent behavior is defined as overt and intentional physically aggressive behavior against another person." Based on the idea of human nature, scientists do agree violence is inherent in humans. Among prehistoric humans, there is archaeological evidence for both contentions of violence and peacefulness as primary characteristics. Since violence is a matter of perception as well as a measurable phenomenon, psychologists have found variability in whether people perceive certain physical acts as "violent". For example, in a state where execution is a legalized punishment we do not typically perceive the executioner as "violent", though we may talk, in a more metaphorical way, of the state acting violently. Likewise, understandings of violence are linked to a perceived aggressor-victim relationship: hence psychologists have shown that people may not recognise defensive use of force as violent, even in cases where the amount of force used is significantly greater than in the original aggression. The concept of violence normalization is known as socially sanctioned, or structural violence and is a topic of increasing interest to researchers trying to understand violent behavior. It has been discussed at length by researchers in sociology, medical anthropology, psychology, psychiatry, philosophy, and bioarchaeology. Evolutionary psychology offers several explanations for human violence in various contexts, such as sexual jealousy in humans, child abuse, and homicide. Goetz (2010) argues that humans are similar to most mammal species and use violence in specific situations. He writes that "Buss and Shackelford (1997a) proposed seven adaptive problems our ancestors recurrently faced that might have been solved by aggression: co-opting the resources of others, defending against attack, inflicting costs on same-sex rivals, negotiating status and hierarchies, deterring rivals from future aggression, deterring mate from infidelity, and reducing resources expended on genetically unrelated children." Goetz writes that most homicides seem to start from relatively trivial disputes between unrelated men who then escalate to violence and death. He argues that such conflicts occur when there is a status dispute between men of relatively similar status. If there is a great initial status difference, then the lower status individual usually offers no challenge and if challenged the higher status individual usually ignores the lower status individual. At the same an