Killer ape theory
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The killer ape theory or killer ape hypothesis is the theory that war and interpersonal aggression was the driving force behind human evolution. It was originated by Raymond Dart in the 1950s; later it was developed further in African Genesis by Robert Ardrey in 1961.
According to the theory, the ancestors of humans were distinguished from other primate species by their greater aggressiveness and this aggression remains within humanity, which retains many murderous instincts.
The theory gained notoriety for suggesting that the urge to do violence was a fundamental part of human psychology. The hunting hypothesis is often associated with the theory, because of similarities and because Robert Ardrey has developed both.
The expression killer ape does not mean an outstanding aggressive kind of ape; in fact the term refers to anthropological analysis of human aggression. Accordingly, the killer ape is a notably belligerent species on which our instincts might be rooted, because this very ancestor could establish itself due to its special aggression.
The predatory transition from ape to human
The step from ape to human
The question is what exactly caused the evolutionary step from ape to human. Basically, there are three versions: the increase of brain size, the acquisition of speech, or upright posture. Smith excludes this last option; otherwise the traditional erect gibbon would be a possible ancestor of humans. For him, the most relevant differentiator was the bigger brain. It would have made the bipedal movement possible and would have accelerated the enlargement through common use of its hands, which are no longer needed for locomotion.
The "Taung Child"
This approximately 2.5 million year old cranial bone, also known as “Taung Child”, was a first proof of bipedal apes. Robert Broom (1866–1951), primarily a Scottish physician, who spent his life as an archeologist in Australia since 1892, agreed to this statement, too. Five years later he decided to spend the rest of his life in South Africa. His excavations from 1946 pointed into the same direction, when he also discovered bones from the Australopithecus africanus.
However, further examinations showed that, in these cases, the size of the brain was not to be equated with the evolution’s level. In fact, it is much more popular to connect the accomplishment of more and more complex movements directly with an evolutionary response, which caused the brain to grow.
Both Dart and Broom, as well as Charles Darwin (1809–1882), agreed that this new type of locomotion brought a remarkable advantage in comparison to other co-specifics, to rival animals or to the quarry.
The findings of Makapan
Osseous findings at a limestone cave located in Makapan, South-Africa, led to the question to what extent this advantage, in combination with a more and more improved skill using tools, affected the behavior of the apes.
These findings showed explicit cracks and fractures, which are likely to be done on purpose. Additionally, there were clubs, bludgeons and spears formed by the long limb bones or the horns of antelopes. This new special weapon leaves small punctured, round, and triangular holes in skulls, depending on how it was formed.
This new development in building weapons shows a clear increase concerning the aggression of the animals.
Dart carries that issue to extremes and equips this new type of ‘carnivorous and killing’ apes (“proto-men” in his own words) with weapons. Furthermore, he describes them as organized in a tribe, so they were able to hunt bigger animals. The ability of making fire and remarkable social skills prompt Dart to bring them more in line with humans.
Observations from Sgt. H. B. Potter (Zululand, South Africa) show that this kind of development is still up to date as it is mentioned in The predatory transition from ape to man by Raymond Dart. He describes a pride of baboons that hunts antelopes. Indeed, he admits that this depends on seasonal circumstances, because nutrition was rare. Nevertheless, he proves explicit behavior.
The eating habits
Concerning the eating habits from then until now, Dart argues that there has always been an ambition to eating meat: grubs and insects, bigger mammals and even human flesh (i.e. distinctive cannibalism) are the results.
A deficit from “animal proteins” has to be compensated, so consuming meat is essential to survive.
The comment written by the editor of Dart’s article Dr. Alan H. Kelso shows how few scientists accepted the new ideas of Dart and Ardrey. Not only did Dart require a long time to publish his work, but also the epilogue contains notices like: “Professor Dart’s thesis that the South African apemen, at the stage they were found, were omnivorous, must be considered as proven. Of course, they were only the ancestors of the modern Bushmen and Negroes, and of nobody else.”
Another obvious piece of evidence would be the rejection of Dart’s thesis by a scientific convention at Livingstone (Zambia, Southern Africa), what led Ardrey into writing his book African Genesis. He felt himself forced to defend the opinion of his mentor.
Just as well, the ethologist Konrad Lorenz showed interest before and brought out his book On Aggression (1963). In his introduction he describes rivaling butterfly fish, which defend their territory that leads over to the question, if humans, too, tend to intraspecific behavior.
A 2008 article in Nature by Dan Jones stated that "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 (the Cinderella effect). Chimpanzees have violence between groups which have similarities to raids and violence between human groups in non-state societies. Several studies have found that the death rates from inter-group violence are similar for human non-state societies and chimpanzees. On the other hand, intra-group violence is lower among humans living in small group societies than among chimpanzees. Humans may have a strong tendency to differ between ingroup and outgroup which affects altruistic and aggressive behavior. There is also evidence that both intra-group and inter-group violence were much more prevalent in the recent past and in tribal societies. This suggests that tendencies to use violence in order to achieve goals are affected by society. Reduced inequalities, more available resources, and reduced blood feuds due to better functioning justice systems may have contributed to declining intra-group violence.
References in fiction
Movies such as Planet of the Apes (1968) show that this issue affected common people, too. In fact, it’s based on Pierre Boulle’s novel of the same title, but the content is almost similar to the topic.
This theory can be seen in the opening sequence of 2001: A Space Odyssey, and also appears in the television show Sliders, which made extensive use of the killer ape theory in storyline arcs involving the Kromaggs. (The names of Dart and Ardrey were combined by the professor Arturo character in the series into "Drayer" who purportedly came up with his world's "killer ape theory".)
- Ardrey, Robert (1961). African Genesis: A Personal Investigation Into the Animal Origins and Nature of Man. New York: Atheneum Books. ISBN 978-0-00-211014-3. LCCN 61015889. OCLC 556678068.
- Dart, Raymond Arthur (1953). "The Predatory Transition from Ape to Man". International Anthropological and Linguistic Review. 1 (4): 201–217. ISSN 0534-6649.
- Lorenz, Konrad (1966). On Aggression. London: Methuen Publishing. ISBN 978-0-415-28320-5. LCCN 67072318. OCLC 72226348.
- Jones, D. (2008). "Human behaviour: Killer instincts". Nature. 451 (7178): 512–515. doi:10.1038/451512a. PMID 18235473.