Human evolution theory utilizing concepts of neoteny & female sexual selection
An etiology of neuropsychological disorders such as autism and dyslexia, and the origin of left handedness.
"It has been speculated that bonobos evolved through retention of juvenile characteristics into adulthood, a process known as neoteny. For example, the smaller skull of the adult bonobo reminded both Schwarz and Coolidge of a juvenile chimpanzee. Bonobos also keep their white tail-tufts, which chimpanzees lose after weaning age. The voices of adult bonobos are as shrill as those of juvenile chimpanzees, and even the frontally oriented vulva is considered a neotenous characteristic, also present in our own species." (De Wall, F. & Lanting, F. (1997) Bonobo. Univ. of California Press: Berkeley p. 27)
"In bonobos, however, male alliances are little developed, which allows females to exert much greater influence. As a result, a relatively young adult male can reach a top position provided his mother is of high rank. On the other hand, males whose mothers are over the hill, or dead, tend to drop in rank. This brings us to perhaps the most puzzling aspect of bonobo society: females often dominate males. With a few notable exceptions, such as spotted hyenas and the lemurs of Madagascar, male dominance is the standard mammalian pattern. The reason is not hard to guess: males usually outweigh females and possess weapons, such as horns, tusks, or fangs, that are absent or much reduced in females." (De Wall, F. & Lanting, F. (1997) Bonobo. Univ. of California Press: Berkeley p. 76)
"Similarly, observers at the Belgian animal park of Planckendael reported that if a male tried to harass a female, all the females would band together to chase him off. That such behavior is not restricted to captivity is evident from observations at Wamba. According to Kano, males sometimes provoke counterattacks from a mass of females: "A group of males will not attack a female, but the opposite can occur." At the center of a traveling party, one usually finds high-ranking females close together. Their sons are allowed to enter this aggregation, but adult males without mothers tend to stay at the periphery. The picture emerging from Wamba, then, is one of a female-centered society, in which even the male rank order is largely dictated by mothers." (De Wall, F. & Lanting, F. (1997) Bonobo. Univ. of California Press: Berkeley p. 78)
"At the zoo, the average bonobo initiates sex once every one and a half hours, whereas the average chimpanzee does so once every seven hours. In the wild, the frequencies are no doubt lower. Many of the contacts, particularly those with the very young, are not carried through to the point of sexual climax. The partners merely pet and fondle each other. Even the average copulation between adults is quick by human standards: 13 seconds at the San Diego Zoo, and 15 seconds at Wamba. Instead of an endless orgy, we see a social life peppered by brief moments of sexual activity." (De Wall, F. & Lanting, F. (1997) Bonobo. Univ. of California Press: Berkeley p. 105)
"Despite the absence of stable mate bonds, bonobos share with us a dramatically extended sexual receptivity. Females are most willing to engage in sex when they are maximally swollen; during this phase mating males also thrust faster---perhaps reflecting greater arousal. Increased receptivity has been achieved by extending the period of genital swelling. Whereas the chimpanzee has a menstrual cycle of approximately thirty-five days, the bonobo's is closer to forty-five days, and the period of swelling covers a greater portion of the cycle (75% compared to 50% in the chimpanzee). In addition, bonobo females resume swellings within a year after having given birth---when they are definitely not yet fertile---which further adds to the amount of time when they are sexually attractive to males. These characteristics make for quite a contrast: the chimpanzee female is receptive less than 5 percent of her adult life, whereas the bonobo female is so nearly half the time." (De Wall, F. & Lanting, F. (1997) Bonobo. Univ. of California Press: Berkeley p. 107)