Thekiller ape theory orkiller ape hypothesis is the theory thatwar and interpersonalaggression was the driving force behindhuman evolution. It was originated byRaymond Dart in his 1953 article "The predatory transition from ape to man"; it was developed further inAfrican Genesis byRobert Ardrey in 1961.[1] The theory gained notoriety for suggesting that the urge toviolence was a fundamental part of humanpsychology. It is associated with thehunting hypothesis, also developed by Ardrey.
According to the theory, the ancestors of humans were distinguished from otherprimate species by their greater aggressiveness, and this aggression is the source of humanity'smurderous instincts.
However, subsequent research has shown that bothchimpanzees andbonobos may exhibit aggressive behaviors over 100 times more often than humans.[2]
The theory has variations as to what kind of violence served as the evolutionary catalyst: one-on-one aggression or group-based aggression.
Several theories suggest the primary reason humans evolved bipedalism was to conserve energy while running, and to free the use of upper limbs.[citation needed] The killer ape theory posits that violence was a driving factor in evolving bipedalism, freeing the upper limbs to wield weapons.[citation needed]
InCreatures of Cain: The Hunt for Human Nature in Cold War America by Erika Lorraine Milam (2018), she states that, "in the 1970s, the theory unraveled altogether when primatologists discovered that chimpanzees also kill members of their own species." This still does not answer whether interpersonal violence derives from biological or social factors.
EthologistKonrad Lorenz showed interest in similar ideas in his bookOn Aggression (1963).[3] In his introduction, he describes how rivalbutterfly fish defend their territories, leading him to raise the question of whether humans, too, tend to intraspecific conflict.
A 1984 article said Dart's evidence was slim, and was refuted by paleontologists in the early 1970s, in particularCK Brain andElisabeth Vrba.[4]
A 2008 article inNature by Dan Jones stated, "A growing number of psychologists, neuroscientists, and anthropologists have accumulated evidence that understanding many aspects of antisocial behaviour, including violence and murder, requires the study of brains, genes, and evolution, as well as the societies those factors have wrought." Evolutionary psychologists generally argue that violence is not done for its own sake, but is a by-product of goals such as higher status or reproductive success. Some evolutionary psychologists argue that humans have specific mechanisms for specific forms of violence such as against stepchildren (theCinderella effect).Chimpanzees have violence between groups, which are similar to raids and violence between human groups in nonstate societies, and produce similar death rates.[5][6] On the other hand, intragroup violence is lower among humans living in small-group societies than among chimpanzees. Humans may have a strong tendency to differ betweeningroup and outgroup, which affects altruistic and aggressive behavior. Also, evidence exists that both intragroup and intergroup violence were much more prevalent in the recent past and in tribal societies. This suggests that tendencies to use violence to achieve goals are affected by social mores. Reduced inequalities, more available resources, and reducedblood feuds due to better-functioningjustice systems may have contributed to declining intragroup violence.[7]
The idea that man is naturally warlike has been challenged, for example in the bookWar, Peace, and Human Nature (2013), edited byDouglas P. Fry.[8] TheSeville Statement on Violence, released under UNESCO auspices in 1986, specifically rejects any genetic basis to violence orwarfare though is considered outdated in light of more contemporary studies. More modern research and criticism has focused on misinterpretations of fossil evidence, lack of research into other apes, and the political climate of theCold War.[9][10]
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The association of violence with a dramatic leap in human evolution can be seen in the opening sequence of2001: A Space Odyssey.
The television showSliders made extensive use of the killer ape theory in storyline arcs involving the Kromaggs.
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