The causes of violent behavior in humans are often a topic of research in psychology. Neurobiologist Jan Volavka emphasizes that for those purposes, "violent behavior is defined as intentional physically aggressive behavior against another person."[84] 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.[85] 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.[86] The "violent male ape" image is often brought up in discussions of human violence. Dale Peterson and Richard Wrangham in "Demonic Males: Apes and the Origins of Human Violence" write that violence is inherent in humans, though not inevitable. However, William L. Ury, editor of a book called "Must We Fight? From the Battlefield to the Schoolyard—A New Perspective on Violent Conflict and Its Prevention" criticizes the "killer ape" myth in his book which brings together discussions from two Harvard Law School symposiums. The conclusion is that "we also have lots of natural mechanisms for cooperation, to keep conflict in check, to channel aggression, and to overcome conflict. These are just as natural to us as the aggressive tendencies."[87] James Gilligan writes violence is often pursued as an antidote to shame or humiliation.[88] The use of violence often is a source of pride and a defence of honor, especially among males who often believe violence defines manhood.[89] Steven Pinker in a New Republic article "The History of Violence" offers evidence that on the average the amount and cruelty of violence to humans and animals has decreased over the last few centuries.[90] Pinker's observation of the decline in interpersonal violence echoes the work of Norbert Elias, who attributes the decline to a 'civilizing process', in which the state's monopolisation of violence, the maintenance of socioeconomic interdependencies or 'figurations', and the maintenance of behavioural codes in culture all contribute to the development of individual sensibilities, which the increase repugnance individuals towards violent acts.[91] Criminologist Steve Hall notes that the decline in violence in the West since the late 14th century has been accompanied by a large rise in less violent forms of acquisitive crime. In a complex process he names 'pseudo-pacification', he argues that the capitalist system and its attendant culture of competitive individualism does not genuinely 'civilize' populations or eliminate the violence that structured the Dark Ages. Instead they stimulate aggressive libidinal energy but sublimate it into a form that is both socially acceptable and economically functional: i.e. pacified competition over symbols of social status. This fuels consumer demand in the economy at the same time as it creates and reproduces the pacified cultural climate needed for production and trading relations to function properly. In social spaces where economic participation is difficult or behavioural codes and regulatory systems are lax, the powerful libidinal energy generated by this dynamic yet fragile process fails to be sublimated and is practiced in the unrefined form of physical violence.[92] Evolutionary psychology offers several explanations for human violence in various contexts. 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."[93] 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 environment of great inequalities between people may cause those at the bottom to use more violence in attempts to gain status.