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 his 1953 article "The predatory transition from ape to man"; it was developed further in African Genesis by Robert Ardrey in 1961. [1] The theory gained notoriety for suggesting that the urge to violence was a fundamental part of human psychology. It is associated with the hunting hypothesis, also developed by Ardrey.
According to the theory, the ancestors of humans were distinguished from other primate species by their greater aggressiveness, and this aggression is the source of humanity's murderous instincts.
However, subsequent research has shown that both chimpanzees and bonobos 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 ]
In Creatures 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.
Ethologist Konrad Lorenz showed interest in similar ideas in his book On Aggression (1963). [3] In his introduction, he describes how rival butterfly 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 1970's, in particular CK Brain and Elisabeth Vrba. [4]
A 2008 article in Nature 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 (the Cinderella 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 between ingroup 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 reduced blood feuds due to better-functioning justice systems may have contributed to declining intragroup violence. [7]
The idea that man is naturally warlike has been challenged, for example in the book War, Peace, and Human Nature (2013), edited by Douglas P. Fry. [8] The Seville Statement on Violence, released under UNESCO auspices in 1986, specifically rejects any genetic basis to violence or warfare 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 the Cold War. [9] [10]
 | This article needs additional citations for verification .(May 2023) |
The association of violence with a dramatic leap in human evolution can be seen in the opening sequence of 2001: A Space Odyssey .
The television show Sliders made extensive use of the killer ape theory in storyline arcs involving the Kromaggs.
Ardipithecus is a genus of an extinct hominine that lived during the Late Miocene and Early Pliocene epochs in the Afar Depression, Ethiopia. Originally described as one of the earliest ancestors of humans after they diverged from the chimpanzees, the relation of this genus to human ancestors and whether it is a hominin is now a matter of debate. Two fossil species are described in the literature: A. ramidus, which lived about 4.4 million years ago during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago. Initial behavioral analysis indicated that Ardipithecus could be very similar to chimpanzees, however more recent analysis based on canine size and lack of canine sexual dimorphism indicates that Ardipithecus was characterised by reduced aggression, and that they more closely resemble bonobos.
Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped, meaning 'two feet'. Types of bipedal movement include walking or running and hopping.
The chimpanzee, also simply known as the chimp, is a species of great ape native to the forests and savannahs of tropical Africa. It has four confirmed subspecies and a fifth proposed one. When its close relative the bonobo was more commonly known as the pygmy chimpanzee, this species was often called the common chimpanzee or the robust chimpanzee. The chimpanzee and the bonobo are the only species in the genus Pan. Evidence from fossils and DNA sequencing shows that Pan is a sister taxon to the human lineage and is thus humans' closest living relative.
Homininae, is a subfamily of the family Hominidae (hominids). This subfamily includes two tribes, Hominini and Gorillini, both having extant species as well as extinct species.
The bonobo, also historically called the pygmy chimpanzee, is an endangered great ape and one of the two species making up the genus Pan. While bonobos are, today, recognized as a distinct species in their own right, they were initially thought to be a subspecies of Pan troglodytes, because of the physical similarities between the two species. Taxonomically, members of the chimpanzee/bonobo subtribe Panina—composed entirely by the genus Pan—are collectively termed panins.
Australopithecus (, OS-trə-lə-PITH-i-kəs, -loh-; or is a genus of early hominins that existed in Africa during the Pliocene and Early Pleistocene. The genera Homo, Paranthropus, and Kenyanthropus evolved from some Australopithecus species. Australopithecus is a member of the subtribe Australopithecina, which sometimes also includes Ardipithecus, though the term "australopithecine" is sometimes used to refer only to members of Australopithecus. Species include A. garhi, A. africanus, A. sediba, A. afarensis, A. anamensis, A. bahrelghazali, and A. deyiremeda. Debate exists as to whether some Australopithecus species should be reclassified into new genera, or if Paranthropus and Kenyanthropus are synonymous with Australopithecus, in part because of the taxonomic inconsistency.
The aquatic ape hypothesis (AAH), also referred to as aquatic ape theory (AAT) or the waterside hypothesis of human evolution, postulates that the ancestors of modern humans took a divergent evolutionary pathway from the other great apes by becoming adapted to a more aquatic habitat. While the hypothesis has some popularity with the lay public, it is generally ignored or classified as pseudoscience by anthropologists.
The genus Pan consists of two extant species: the chimpanzee and the bonobo. Taxonomically, these two ape species are collectively termed panins. The two species were formerly collectively called "chimpanzees" or "chimps"; if bonobos were recognized as a separate group at all, they were referred to as "pygmy" or "gracile chimpanzees". Together with humans, gorillas, and orangutans they are part of the family Hominidae. Native to sub-Saharan Africa, chimpanzees and bonobos are currently both found in the Congo jungle, while only the chimpanzee is also found further north in West Africa. Both species are listed as endangered on the IUCN Red List of Threatened Species, and in 2017 the Convention on Migratory Species selected the chimpanzee for special protection.
Raymond Arthur Dart was an Australian anatomist and anthropologist, best known for his involvement in the 1924 discovery of the first fossil found of Australopithecus africanus, an extinct hominin closely related to humans, at Taung in the North of South Africa in the Northwest province.
Franciscus Bernardus Maria de Waal was a Dutch-American primatologist and ethologist. He was the Charles Howard Candler Professor of Primate Behavior in the Department of Psychology at Emory University in Atlanta, Georgia, director of the Living Links Center at the Yerkes National Primate Research Center at Emory, and author of numerous books including Chimpanzee Politics (1982) and Our Inner Ape (2005). His research centered on primate social behavior, including conflict resolution, cooperation, inequity aversion, and food-sharing. He was a member of the United States National Academy of Sciences and the Royal Netherlands Academy of Arts and Sciences.
On Aggression is a 1963 book by the ethologist Konrad Lorenz; it was translated into English in 1966. As he writes in the prologue, "the subject of this book is aggression, that is to say the fighting instinct in beast and man which is directed against members of the same species."
Robert Ardrey was an American playwright, screenwriter and science writer perhaps best known for The Territorial Imperative (1966). After a Broadway and Hollywood career, he returned to his academic training in anthropology in the 1950s.
Richard Walter Wrangham is an English anthropologist and primatologist; he is Professor of Biological Anthropology at Harvard University. His research and writing have involved ape behavior, human evolution, violence, and cooking.
A facultative biped is an animal that is capable of walking or running on two legs (bipedal), as a response to exceptional circumstances (facultative), while normally walking or running on four limbs or more. In contrast, obligate bipedalism is where walking or running on two legs is the primary method of locomotion. Facultative bipedalism has been observed in several families of lizards and multiple species of primates, including sifakas, capuchin monkeys, baboons, gibbons, gorillas, bonobos and chimpanzees. Several dinosaur and other prehistoric archosaur species are facultative bipeds, most notably ornithopods and marginocephalians, with some recorded examples within sauropodomorpha. Different facultatively bipedal species employ different types of bipedalism corresponding to the varying reasons they have for engaging in facultative bipedalism. In primates, bipedalism is often associated with food gathering and transport. In lizards, it has been debated whether bipedal locomotion is an advantage for speed and energy conservation or whether it is governed solely by the mechanics of the acceleration and lizard's center of mass. Facultative bipedalism is often divided into high-speed (lizards) and low-speed (gibbons), but some species cannot be easily categorized into one of these two. Facultative bipedalism has also been observed in cockroaches and some desert rodents.
Demonic Males: Apes and the Origins of Human Violence is a 1996 book by Richard Wrangham and Dale Peterson examining the evolutionary factors leading to human male violence.
The Territorial Imperative: A Personal Inquiry Into the Animal Origins of Property and Nations is a 1966 nonfiction book by American writer Robert Ardrey. It characterizes an instinct among humans toward territoriality and the implications of this to property ownership and nation building. The Territorial Imperative was influential at the time, and encouraged public interest in human origins.
African Genesis: A Personal Investigation into the Animal Origins and Nature of Man, usually referred to as African Genesis, is a 1961 nonfiction work by the American writer Robert Ardrey. It posited the hypothesis that man evolved on the African continent from carnivorous, predatory ancestors who distinguished themselves from apes by the use of weapons. The work bears on questions of human origins, human nature, and human uniqueness. Although some of his ideas were refuted by later science, it was widely read and continues to inspire significant controversy.
The Social Contract: A Personal Inquiry into the Evolutionary Sources of Order and Disorder is a 1970 book by Robert Ardrey. It is the third in his four-book Nature of Man Series.
The Nature of Man Series is a four-volume series of works in paleoanthropology by the prolific playwright, screenwriter, and science writer Robert Ardrey. The books in the series were published between 1961 and 1976.
The amity–enmity complex theory was introduced by Sir Arthur Keith in his work A New Theory of Human Evolution (1948). He posited that humans evolved as differing races, tribes, and cultures, exhibiting patriotism, morality, leadership and nationalism. Those who belong are part of the in-group, and tolerated; all others are classed as out-group, and subject to hostility: "The code of enmity is a necessary part of the machinery of evolution. He who feels generous towards his enemy... has given up his place in the turmoil of evolutionary competition."
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