Man as the Prayer: The Origin and Nature of Humankind by Yup Lee
Unfortunately, however, even the obsolescence of sexual swellings did not seem to have guaranteed the safety of estrous females and their immatures. As they became obsolete, males could not distinguish between estrous females and anestrous ones. As a result, many males obsessed with mating tried to copulate forcefully with any females they came across. This kind of eccentric behavior has come down through generations of orangutans until today. In fact, forced copulations are known to take place frequently among modern orangutans,43 in stark contrast to other species of great apes.
Among common chimpanzees, forced copulations are observed but very rarely.44 On the other hand, they are not observed among pygmy chimpanzees.45 Such a case is not reported among gorillas, either, to my knowledge. Thus, orangutans are an exceptional case among nonhuman primates, in respect of forced copulation.46
Unfortunately, male orangutans seem to have gone as far as copulating forcefully with pregnant females probably with the result that many pregnant ones suffered abortion, causing their population to dwindle. If the situation had not been reversed. they would have disappeared from the face of the Earth.
Females were put under severe stress. They had to find out a way to repulse irresponsible males at least while they were pregnant. But they could not use force to keep males at bay because they were physically no match for males. They were helpless.
One day, a pregnant orangutan which was under severe stress in the hands of male molesters may have begun to exhibit abnormal sexual swellings of which the color was visibly whitish. It was unusual because a pregnant female displayed genital swellings and because they turned whitish rather than reddish.
Surprisingly, however, many orangutan males began to avoid her probably because her whitish, swollen perineum was too strange and unattractive to approach. Consequently, this outcast female succeeded in producing more children than the others.
As her descendants prospered, the strange physical changes became a rule rather than an exception. Indeed, disused sexual swellings appear to have been somehow or other recycled and reused among orangutan females in a very unique way to ward off love-hungry males successfully.
As noted above, sexual swellings may have come into existence under the unusual circumstances where estrous females had great difficulties in finding mates. As soon as all the females of the species involved acquired sexual swellings, they had no more troubles with locating mates.
Once afflicted with the Cinderella syndrome, however, some females began to show bigger and bigger swellings, igniting runaway competition for mates among themselves. This trend went out of control until some females began to exhibit sexual swellings far beyond the time of ovulation. Their estrous phase became abnormally prolonged due to the severe psychological and physical stress incurred by unbearable competition among themselves. In other words, extended sexual swellings seem to have originated from an abnormal lengthening of estrous cycles that were often anovulatory.
If true, this turn of events posed a new serious challenge to the males because they had to sort out ovulating females for fertile matings. Probably, many males may have engaged in wasteful matings with estrous but anovulatory females, having been blinded and misled by the visual sign of sexual swellings.
Probably for these reasons, the extended sexual swellings were originally uncommon and aberrant ones. However, they seem to have brought about unexpected benefits to those females involved. It is speculated that the pathological prolongation of the sexual swellings and subsequent obscurity of ovulation drew more males and kept them longer around the females,47 leading ultimately to the substantial increase of their fitness. As a consequence, the aberrant variation was retained and passed on to the next generation. As time passed, all female descendants of the lineage came to possess an extended period of sexual swellings with the result that they came to mate regularly with numerous males during the time of sexual receptivity.
Extended sexual swellings, however, do not seem to have moderated interfemale competitions for male attentions. They appear to have flared up more intensely so that some females started going to rut at different times as much as possible, to avoid unbearable competitions.
These changes in female physiology and morphology seem to have caused a fundamental transformation in their social organization. Because each female came into estrous at different times, with an extended period of sexual swellings, males were forced to hang around competing females, resulting eventually in the formation of a multimale group. In this sense, the morphological changes of extended sexual swellings and the multimale social structure seem to have evolved in tandem, among some primates.48
In addition, a promiscuous mating system seems to be a by-product of extended sexual swellings since the latter made it impossible for any single male or female to monopolize mating opportunities.
Taken together, it can be assumed that orangutans initially had a multimale community in which they practiced promiscuity; and such a social system had been changed later under the impact of severe intermale competition.
As the intermale competition went out of control, female orangutans may have avoided males as much as possible. To save their lives, females ran away from males to hide somewhere in the forest. As a result, each of the adult female orangutans came to live in solitude under the cover of the shadows of trees. Each of the male orangutans came to live alone, too, because they could not tolerate one another's presence.
With time, a pattern seems to have formed: dominant adult males secure larger ranges that encompass the smaller, overlapping ranges of two or more adult females; other adult males who can not secure their own ranges have no choice but to rove over wide areas as transients in quest of food and mates.49
Orangutans seem to have forsaken their initial mating system of promiscuity and have adopted that of temporary consortship. Because females avoided males as far as possible, it can be reasoned that their system of a temporary sexual consortship did not develop into a permanent one, i.e., monogamy. (more)
Copyright © 2000 Yup Lee. All rights reserved.