Man as the Prayer: The Origin and Nature of Humankind by Yup Lee
If early orangutans gave up promiscuity for temporary consortship, early gorillas did that for polygamy. As I will explain below, male proto-gorillas fought one another fiercely over estrous females the way early male orangutans probably did a long time ago. But female proto-gorillas had no place to run away and hide. Thus, they had no choice but to become concubines of a dominant male, forming a harem. Bound by a single male master, their sexual swellings lost the reason for existence. As a result, they degenerated, becoming smaller and shorter.
Even though female orangutans do not display sexual swellings and female gorillas exhibit tiny, short-term ones which is more appropriately called a labial swelling,50 it is speculated that they had extended ones in the past. If so, extended sexual swellings, a multimale social structure and a promiscuous mating system are assumed to have been initial characteristics of the great apes. If so, the last common ancestors of gorillas, chimpanzees and humans may have had the same characteristics. It would have been the case for our distant ancestors as well.
There is another thing about sexual swellings that merits our attention. It is the inspection of female genitalia by males, a habit which is not uncommon among many species of mammals. Males check orally and/or manually the genital region of their potential mates before copulation.51
Among many species of modern-day prosimians or lower primates, it is common for males to sniff at or lick genitals of estrous females. Such behavior is observed even among several species of monkeys.52 But among most of the Old World monkeys and the lesser apes, such behavior can not be observed. What is interesting, however, is that such behavior is found among extant great apes like common chimpanzees which are one of our evolutionary "cousins."
Among common chimpanzees, scrutiny of female genitals is a commonplace. They are known to inspect female genitals closely by using their eyes, fingers, mouth and/or nose.53 Orangutans are known to put their mouths on female genitals usually before mating.54 But adult gorillas are not observed to do such a thing.55 Needless to say, this does not necessarily mean that their ancestors did not do that.
Even though the inspection of female sexual organs by males appears outwardly routine and habitual, it seems to be very serious one for the animals concerned because it is directly relevant to their fitness or reproductive success that plays a pivotal role in the course of the evolution of the species concerned. It may be even more serious for the animal species such as common chimpanzees which have extended sexual swellings that obscure ovulation.
Taken together, it is speculated that the earliest great apes did not sniff at or lick female genitals. Oral and/or manual investigation of female genitalia might have evolved among their descendants in tandem with the development of extended sexual swellings as well as the multimale social structure.
Prolongation of sexual swellings appears to have made a fundamental impact upon the mating behavior of the animal involved. In the past, a male who warded off rivals had a fairly good chance of siring offspring even if he could not monopolize access to an estrous female. But, as the time of sexual swellings became lengthened, females came to mate with more and more males during the time of estrus which was far out of harmony with that of ovulation.
All of sudden, dominant males got to face a serious problem: their chance of fathering children became greatly reduced. Their fathership, a prize of life-and-death struggle, was in great danger. However strong they were physically, their fortune was in the hands of females. They lost control of their own fortune. The basic rules of the game had changed to their disadvantage. In this sense, the advent of the extended sexual swellings may have been a turning point for early great apes.
Males faced a serious challenge brought about by the introduction of extended sexual swellings. To solve the problem, males were forced to develop their ability to pinpoint the time of ovulation, by scrutinizing the female genital region with all available means. Eventually, an effective method to verify ovulation seems to have been developed. With time, it was modified according to the needs of the species implicated.
Among common chimpanzees which basically practice promiscuity in a multimale social structure, the ovulation checkup is still practiced but its seriousness appears to have been lessened in the course of time. Among orangutans which mainly practice temporary consortship, its modified form is still practiced in a seemingly cursory fashion. But male orangutans may be very serious about the matter. In contrast, the art of checking female ovulation had been abandoned completely among polygynous gorillas.
What about hominids? Did our ancestresses have cyclical sexual swellings? Did our ancestors regularly inspect them before love-making? The answers are "yes" in both cases.
Mature human females of today have cycles of menstruation, but do not exhibit anything like sexual swellings. They generally have neither a specific period of estrus, nor outward signs of estrus. In addition, mature human males of the present have never thought or heard about the close examination of female genitalia to pinpoint the time of ovulation. Even modern gynecologists may not be able to discover such a thing only with their eyes, noses and/or tongues. Even if so, it should not be hastily concluded that hominids of the past were like those of today.
Rhesus monkeys are found to have special chemical substances in their vaginal secretion that stimulate their mates sexually.56 The same may be true for human beings. Tests performed by an Austrian scientist, Astrid Jutte hints that male humans sense and react physiologically to the odor of ovulating females.57 (more)
Copyright © 2000 Yup Lee. All rights reserved.