Human evolution theory utilizing concepts of neoteny & female sexual selection
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T. Kano

The Last Ape: Pygmy Chimpanzee Behavior and Ecology: Bibliographical Excerpts

"First, the most important fission-fusion unit of the pygmy chimpanzee is the mother-infant family, but this is also true for the common chimpanzee. A point in which they differ is that in the common chimpanzee, only mother and her infant and juveniles are included in mother-infant families, but among the pygmy chimpanzees, even mature sons join in." ... On the other hand, since young adult male pygmy chimpanzees follow their mothers, the male bond between them is not as firm as that between common chimpanzee males. But friendship between adult females pygmy chimpanzees (that is, mothers) is great. Mother-offspring families gather and usually form a large party. Because the party includes adult sons, large multi-male parties are formed that become natural reproductive units. In this way, the mother is the core of pygmy chimpanzee society, and the males lead a life following their mothers." (Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology; Stanford Univ. Press, Standord p. 91)

"Pygmy chimpanzees are promiscuous. All kinds of pairings among group members are possible, except between a mother and her mature son. Consequently, members of the same sex within a group can all be sexual competitors. At the feeding site, however, interference by other mature individuals before, during, or after copulation ws seen in only 33 out of 515 copulations. That is, interference during copulation occurred at the inconsequentially low rate of 7%." (Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology; Stanford Univ. Press, Standord p. 145)

"In pygmy chimpanzee society, the primary role of copulatory behavior is undoubtedly to enable the male-female coexistence, not to conceive offspring. In this case, we ought to recognize copulation primarily as a social behavior, with "reproduction" as a secondary function." (Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology; Stanford Univ. Press, Standord p. 162)

"A male pygmy chimpanzee of Wamba spends a great deal of time with his mother. When a son enters adulthood, he never displays dominant behavior toward his mother." (Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology; Stanford Univ. Press, Standord p. 171)

"Here again, we see the influence of the mother-son relationship on social structure. Continued intimacy in the mother-son relationship is apparently an obstacle to a strong alliance of adult males united by the "male bond." The mother can influence the male's class or rank in an even more direct way. Four cases have been reported of young males who rose in rank within a short period of time. The common characteristic of all these young males was that their mothers were middle-aged to old females respected by other individuals." (Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology; Stanford Univ. Press, Standord p. 183)

"...there may be a "female bond." Several examples have been reported in which a male provoked a female and a group of females cooperated in a counterattack. A group of males will not attack a female, but the opposite can occur. When the victim is a low-ranking male, we expect that a high-ranking male is on the attacking side, and it becomes a serious matter. When the victim is a high-ranking male and other males are not involved, the victim can certainly be defeated by a mass of troublesome middle-aged females. From the beginning, common chimpanzee research has revealed a low frequency of social interactions between females. Females do not associate with each other much and, in particular, they rarely engage in friendly behaviors such as grooming (Nishida, 1970). By contrast, female pigmy chimpanzees are very sociable. In particular, females with infants and juveniles (essentially all multiparous females) forage in close company, but aggressive interactions rarely occur. At resting time, grooming between females is common, although less frequent than between males and females." (Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology; Stanford Univ. Press, Standord p. 188-9)

"In primate societies, the mother-offspring relationship is the only social structure that has increasingly developed friendly, mutual action over a history of 70 million years. Attachment to a specific individual must have originated in that structure. That is why I presented the hypothesis that the extended family composed of a mother, sons, and immigrant females is the original form of the human family. As a preliminary condition of pair formation, the attachment of offspring to the mother must be sufficiently established." (Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology; Stanford Univ. Press, Standord p. 219)

"the courtship display of pygmy chimpanzees, like many animals, are performed by a male and directed toward a female. There are various patterns of courtship displays. In the first form, a male attracts the attention of a female who is far enough away that she cannot be touched, faces her, and spreads his thighs. While exposing his erect penis, he sits or moves his squatting body up and down, forward and backward, or side to side. Some males stick out their chest, and some stoop forward while they are displaying. Their hands are extended and moved in any direction according to individual preference, upward, sideways, and, most often, forward, as if to beckon the female. If the female does not respond to this first form of courtship display, the male often changes to a second form of display. He approaches the female, sits or stands bipedally, and extends his hand, lightly touching and then releasing her head, shoulder, back, or knee. His body slowly moves forward and back and side to side. One male moved his body violently up and down in the first display form, but when the female approached, he slowed his movements and touched her body cautiously and gently as if touching a fragile article. A female responds positively to a courtship display by standing when the male is near or by standing up and approaching the male. After this, she exhibits "presenting" behavior, in which she presents her genitalia to the male; he responds by mounting and copulating with her. If a female does not exhibit presenting behavior, the male retreats to a place separated from the female by several meters and resumes the courtship display. Repetition of the courtship display, followed by the female's approach, the male's retreat, and the next courtship display, recurs several times. We often saw a male draw a female away from other individuals, go up into a tree, and copulate with her there. Females also solicit copulation, approaching the presenting to males even though they have shown no sign of courtship. Of copulations observed in their entirety during 1984, 71 were examples in which the male approached or first made a courtship display and 25 were examples in which the female approached and solicited copulation. ... In pygmy chimpanzees, every copulation is invariably preceded by female presentation, which takes two forms. In one form, the female stands quadrupedally, facing away from the male and thrusting her genitalia in front of the male; this is followed by dorso-ventral copulation. In the other form, the female lies on her back in front of the male, spreads her thighs, raises her buttocks, adjust herself, and shows her sexual organs; the male approaches and copulates ventro-ventrally." (Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology; Stanford Univ. Press, Standord p. 140-1)



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