Library of Excerpts

Neoteny: Aggression and Sperm Count Issues

"The more intelligent transitional female (remember, it is her offspring who will be most likely to survive) could use her intelligence to select males for copulation. In other words, increases in intelligence and a richer, more sophisticated communicatory repertoire mean the mating system itself could become more complex. I hypothesize that the mating system was changing so as regularly to include female discrimination and choice of sex partners in terms of a number of characteristics. Females probably had sex more frequently with those males who were around often, playing with offspring, helping in protection, occasionally sharing meat and foraged plants, and who were generally friendly. With females choosing the less disruptive males, there also would be less likelihood that males having sex with mothers might accidentally injure offspring. To the extent that the ability to learn to be more sociable has been enhanced by genetic changes that have augmented our human potential --- and this is a subject about which little is known --- sexual selection in the hominid divergence also could have increased the capacity of males for relaxed social interaction. ... What may have been selected for among the transitional hominid males was the capacity to be extremely social but yet sufficiently aggressive when required and an ability to make fine discriminations as to situational necessity. Thus, the males of the transitional population would come to more closely resemble the females than had the males of the ancestral population. ... Much of the selection pressure engendered by female choice of sexual partners was directed toward male social and communicatory behavior, reinforcing the potential and capacity for sociability, social learning, and intelligence." (Tanner, Nancy M. (1981) On Becoming Human: Cambridge University Press, Cambridge p. 164-5)

"By choosing males with low T, females are prolonging the developmental and maturation rates of their male progeny. In humans the relative levels of testosterone (and probably estrogen) in males and females is the primary hormonal intermediary between the eight environmental cues and relative rates of maturation. By prolonging growth, whether explained by heterochronic concepts of neoteny (Montagu, 1956; Gould, 1977) (prolonging child features into adulthood) or by hypermorphosis (Shea, 1989; McKinney and McNamara, 1990) (prolonging all developmental stages), one of the net results is increased brain and cranium size. Prolonging growth rates is achieved in humans by lowering T. Accelerating growth, in effect condensing developmental stages, is achieved by raising T. We believe that there was a feedback loop effect speeding up the process of brain growth. This is similar to the process described by Miller (1994) using Fisher's (1930) runaway theory of sexual selection. It is our hypothesis that song and dance created peculiarities of human consciousness leading to culture, as opposed to evidencing them. Song and dance---in combination with females choosing males with lower T---are primary forces responsible for the exponential rise in brain size in the last 2 million years." ( Lehman A & Bernsten M (1999) Evolution and the Structure of Health and Disease (web link)

“Chimpanzees are reproductively extraordinary among the great apes. They are not strikingly dimorphic for size as are the other two species (Fig 2), but male chimpanzees have enormous scrotal testes, proportionately about 5 and 10 times larger than Pongo and Gorilla, respectively, and a specialized penis more than twice as long as that on the much larger gorilla. Short (1981) has calculated that the testes of an average chimpanzee can sustain sperm production at a level that will produce at least four full-strength ejaculates/day, each containing several times the number of sperm in an average gorilla or orangutan ejaculate.” (Robert L. Smith (1984) Human Sperm Competition. in Sperm Competition and the Evolution of Animal Mating Systems pp. 619)

"...in the chimpanzee, several males mate frequently with the oestroud females, so that each male has to deposit enough sperm to compete with the presence of sperm from other males. For the chimpanzee, therefore, we hypothesize that selection will favour the male that can deposit the largest number of sperm; thus the volume of spermatogenic tissue and hence the testis size is far greater in the chimpanzee than in the gorilla or orangutan. If this is correct, it implies that primates in which more than one male mates with each oestrous female should have larger testes relative to their body weight than those which single-male breeding systems. We have tested this prediction across a wide range of primates, and the results support the hypothesis. The relative size of testes may, therefore, provide a valuable clue to the breeding system of a primate species." (Harcourt AH, Harvey PH, Larson SG, Short RV (1981) Testis weight body weight and breeding system in primates. Nature 293: pp. 55)

"The drop is testicular androgen concentrations (dihydrotestosterone and especially testosterone) is not related at all to nycthemeral fluctuations (29.30). This drop is observed at km 50 but is more pronounced at the arrival. It confirms the results obtained in previous studies on prolonged efforts (19,21). This drop in testosterone levels is rapidly corrected, on the following day, and during the recovery phase and increase in testosteronemia is observed, as if the lower testicular reactivity to effort was followed by a phase of increased secretion, parallel to clinical recovery. ... Two mechanisms can account for a lower gland production of the hormone: -- a persisting significant rise in the levels of circulating epiniphrine could induce a drop in the plasma levels of testosterone by means of reduced testicular production, with unchanged global metabolic clearance (32); --- hypercortisolemia, under the condition that it is prolonged enough, would reduce the plasma levels of testosterone (33,34). This normal profile (hypercortisolemia, hypotestosteronemia) is described in other stress conditions (35,36) and in Cushings's syndrome (37,38,39).: (Morville, R., Pesquies, P.C., Guezennec, C.Y., Serrurier, B.D., Guignard, M. (1979) Plasma variations in testicular and adrenal androgens during prolonged physical exercise in man. Annales D. Endocrinlogie (Paris) 40 (5): 506)

“In Malaya, mean testicular weights of T. glis and T. minor were highest in spring and early summer; 60g and 0.54g fro April-June compared with 0.81g and 0.20g for October-December in these two species (Harrison, 1955).” (Michael, R.P., Wilson, M., & Plant, T.M. (1973) Sexual Behavior of Male Primates and the Role of Testosterone in Comparative Ecology and Behavior of Primates. R.P. Michael and J.H. Crook, eds. New York: Academic Press Pp. 239) (rhesus monkeys?]

[rhesus monkeys]“Following castration, there was a marked decline in the number of ejaculations and intromissions per test for both groups: this was more conspicuous for adults which had a higher level of performance when intact (Fig 5.) Whereas ejaculations ceased entirely in the sub-adult group about 12 weeks after castration, they persisted in some adult males, as did intromissions, throughout the 32 week period in which these observations refer. In contrast, a marked decline in mounting activity was observed during this time in sub-adults, and mounting continued more or less unchanged in the adult group. There was no explanation for the transient increase in mounting by some sub-adults 18 weeks after castration. (Fig.5). These data refer to the initial 32 weeks after castration, but the behavior of the castrated adults was followed for an additional 6-90 weeks. During this extended period of observation, sexual activity declined further, and all four males ceased ejaculating by 109 weeks. Mounting also declined to very low levels (Fig. 8) but, unlike ejaculation and intromission, mounting continued to occur in occasional tests throughout the entire period of study.” (Michael, R.P., Wilson, M., & Plant, T.M. (1973) Sexual Behavior of Male Primates and the Role of Testosterone in Comparative Ecology and Behavior of Primates. R.P. Michael and J.H. Crook, eds. New York: Academic Press Pp. 281-4)

"As we have seen, chimpanzees live in groups where several males may share a female, and therefore there is a premium on the ability to ejaculate often and voluminously---he who does so has the best chance of being the father. This conjecture holds up across all the monkeys and across all rodents. The more they can be sure of sexual monopoly, as the gorilla can, the smaller their testes; the more they live in multimale promiscuous groups, the larger their testes. It began to look as if Short had stumbled on an anatomical clue to a species' mating system: Big testicles equals polygamous females. Could it be used to predict the mating system of species a that had not been studied? For example, very little is known about the societies of dolphins and whales, but a good deal is known of their anatomy, thanks to whaling. They all have enormous testicle, even allowing for their size. The testicles of a right whale weigh more than a ton and account for 2 percent of its body weight. So given the monkey pattern, it is reasonable to predict that female whales and dolphins are mostly not monogamous but will mate with several males. As far as is known, this is the case. The mating system of the bottle-nosed dolphin seems to consist of forcible "herding" of fertile females by shifting coalitions of males and sometimes even the simultaneous impregnation of such a female by two males at the same time---a case of sperm competition more severe than anything in the chimpanzee world. Sperm whales, which live in harems like gorillas, have comparatively smaller testicles; one male has a monopoly over his harem and has no sperm competitors. Let us now apply this prediction to man. For an ape, man's testicles are medium-sized---considerably bigger than a gorilla's. Like a chimpanzee's, human testicles are housed in a scrotum that hangs outside the body where it keeps the sperm that have already been produced cool, therefore increasing their shelf life, as it were. This is all evidence of sperm competition in man. But human testicles are not nearly as large as those of chimps, and there is some tentative evidence that they are not operating on full power (that is, they might once have been bigger in our ancestors): Sperm production per gram of tissue is unusually low in man. All in all, it seems fair to conclude that women are not highly promiscuous, which is what we expected to find." (Ridley 1993: 220-21, The Red Queen)

“The changes in plasma testosterone after castration were extremely rapid, and Fig. 7 shows the levels had fallen by 50% within 30 min of gonadectomy. This was also the case when LH treatment (HCG) prior to castration produced exceptionally high intact plasma levels, and within 24 hr plasma testosterone values were in the range of those of long-term castrates.” (Michael, R.P., Wilson, M., & Plant, T.M. (1973) Sexual Behavior of Male Primates and the Role of Testosterone in Comparative Ecology and Behavior of Primates. R.P. Michael and J.H. Crook, eds. New York: Academic Press Pp. 285) [rhesus monkeys]

"Different prehuman species suggest different levels of sperm competition. Judging from its teeth, Australopithecus africanus was certainly a vegetarian. Like gorillas, the vegetarian australopithecines showed a bigger difference in body size between sexes than men and women do today, suggesting that they were sperm-competition avoiders. Although no one, of course, knows for sure, Robert Smith speculates that physically imposing males bossed relatively sexually faithful females in australopithecine harems. These ancestors would have been very sexist, but the males, violently intolerant of promiscuity, would not have developed large genitals. This sultanlike breeding behavior could well have undergone radical change with the evolution of Homo habilis, "handy man": Smith postulates that subordinate habilis males, scavenging meat and offering pieces of it in exchange for sex, upset the earlier breeding system. The cooperative hunting groups that began with Homo erectus --- our most recent evolutionary predecessor --- ushered in relatively high levels of sperm competition. Homo erectus males were not much larger than Homo erectus females. Homo erectus was a communal species who not only gathered edible plants but hunted mammoths and used fire. Eating and sleeping together in groups --- the sort of cooperative groups needed to hunt --- may have made them far more social, more talkative, and better barterers than their sexually dimorphic australopithecine ancestors. And more promiscuous. It was with Homo erectus, Smith suggests, that people developed their relatively large male genitals." (Margulis, L & Sagan, D. (1991) Mystery Dance, On the Evolution of Human Sexuality: Summit Books, New York pp. 51)

“Thus, some 22 weeks of daily treatment with testosterone, although producing a marked improvement, did not fully restore the behavioral patterns to those observed before castration in either group. This is perhaps more clearly shown in the group data (Fig 9) where for both the sub-adults and adults, ejaculatory performance during testosterone replacement treatment reached only some 50% that of intact levels. However, individual differences in the effects of replacement treatment on behavior were as marked as were the effects of castration. In on male, ejaculation was fully restored in about 16 weeks of treatment whereas, in another male paired with the same females, although ejaculation reappeared earlier, it failed to reach pre-castration levels during the following 6 months of treatment (Fig. 10).” [rhesus monkeys] (Michael, R.P., Wilson, M., & Plant, T.M. (1973) Sexual Behavior of Male Primates and the Role of Testosterone in Comparative Ecology and Behavior of Primates. R.P. Michael and J.H. Crook, eds. New York: Academic Press Pp. 288)

“Masturbation seems a bizarre, maladaptive behavior because it wastes sperm, but the practice is almost universal among U.S. males and is particularly common in adolescents (Kinsey et al. 1948, Sorensen 1973). Masturbation is also commonly observed in some captive primates. It has been said that “primates masturbate, because they can,” but if autoeroticism were maladaptive, the tendency should have been repressed by natural selection. A clue to a possible function is found in the fact that males who do not ejaculate by coitus or masturbation for some period of time experience nocturnal emissions, i.e. spontaneous seminal discharge during sleep. This suggests that stored sperm and/or accessory gland products may have definite “shelf life” after which they are best discarded and replaced with new in order to stay competitive. Another possibility that has not been properly investigated is that frequent ejaculation may activate some feedback machansim (e.g. testosterone/inhibin) to stimulate higher levels of spermatogenesis and accessory gland secretion.” (Robert L. Smith (1984) Human Sperm Competition. in Sperm Competition and the Evolution of Animal Mating Systems pp. 633)

“Testes Size. Although we were unable to predict the magnitude of testes size increase, our predictions were qualitively correct. Testes size increased with body size and the relationship was negatively allometric. For their body size, “genera” in which females are likely to mate with more than one male during estrus have larger testes than those where only one male usually gains access. The hypothesis that sperm competition is important in the correlation between breeding system and testes size requires that multi-male primates, as well as having larger testes, have higher rates of sperm production than single-male or monogamous species. In other words, we need to show that the larger RTS is not merely due to an increase in non-spermatogenic tissue. If the value of the seminiferous tubules is applied as a measure of potential sperm production, our hypothesis is supported. Chimpanzees, baboons, and macaques (Macaca spp.), all with multimale breeding systems, have ratios of tubules to connective tissue in their testes that range from 2.2:1 to 2.8:1; while man, gibbons (Hylobates spp.), and langurs (Presbytis spp.), which are not multi-male have ratios of 0.9:1 to 1.3:1. In addition, the sperm production rate of the rhesus macaque (Maccaca mulatta) is about 23 x 106, while the corresponding value for man in only 4.4 x 106 (Amann et al., 1976, Amann and Howards 1980). These data suggest that multi-male species not only have larger testes but also have a higher sperm production capacity per unit weight of testis tissue. Our measure of RTS may, therefore, underestimate the effects of sperm competition as a selective force increasing sperm production rates. Nevertheless, sperm production is unlikely to be the only reason for differences in RTS among primates. For example, seasonality of breeding could be an important factor; species with a short breeding season and hence periods of intense copulatory activity may need larger testes. Certainly, the multi-male genus Macaca which contains predominantly seasonal breeders has the largest RTS. In this connection, it is interesting to note that the single-male “genera” do not have larger RTS than monogamous primates (on average it is rather less), and sperm production does not, therefore, seem to relate to the number to females that a male serves during the year. As with all comparative studies, aberrant taxa are revealed. Saguinus oedipus has rather larger testes for its body size and a monogamous breeding system; likewise for the Hamadryas baboon with its single-male breeding system. Nevertheless, this study reveals a consistent trend and emphasizes the need for similar studies on other mammalian groups. Among primates, further progress will require studies on the fine structure of primate testes, on sperm production rates and on copulation frequencies and timing in natural populations. Even then, controlled experiments using genetic markers will be necessary to validate correlative evidence. Intrasexual Selection and Sperm Competition Recent surveys of sexual selection (e.g. Halliday 1978) restrict themselves to the traditional distinction made between intra sexual and epigamic selection for access to mates. This chapter has so far considered one component of post copulatory intrasexual selection, sperm competition (Short 1977). Epigamic selection concerning active female choice on the male phenotype develop sexual swellings when they are in estrus. It is generally accepted that these serve to attract males. These species, with one exception, live in multi-male troops and whether sexual swellings are associated with active choice in male (epigamic selection) or passive “choice” (provoking inter-male conflict so that the dominant male achieves access to the female or where males from neighboring troops are enticed to compete with resident males for access) is not known. However, recent comparative studies on primates have indicated a strong influence of intrasexual selection on both sexual dimorphism in body size (Harvey et al. 1978).” (Harvery PH & Harcourt AH (1984) Sperm Competition, Testes Size, and Breeding Systems in Primates. in Sperm Competition and the Evolution of Animal Mating Systems pp. 595-6)

"Pan paniscus shows increase female receptivity, variability in copulatory position, male or female initiation of sexual behavior, differential male and female preferences for copulatory position, and association of food sharing and sexual behavior. Their sexual behavior appears to function in proximate terms as a tension-reduction mechanism. Lowered tension, in turn, facilitates multi-male, multi-female social groups. Lowered levels of aggression and increased sexual activity appear to be associated with paedomorphism, and the behavioral and anatomical/physiological characteristics of the species appear to be a consequence of a feeding ecology that promotes large groupings of the animals at preferential and comparatively rich feeding sites." (Blount, Ben G. (1990) Issues in bonobo (Pan paniscus) sexual behavior. American Anthropologist 92: 702)

"One single gene disorder, fragile X, has recently been discovered that is X-linked, is found predominantly in males, and appears to have a specific association with autism. The clinical features are somewhat variable, but in its most severe form, the affected males are mentally retarded after puberty, have enlarged testicles. They tend to be hypotonic and to have somewhat long faces and large ears, but as children they do not appear particularly dysmorphic (Brondum-Nielsen, 1983). This syndrome of X-linked mental retardation was clinically recognized before the discovery of its association with fragile X and was known as the Martin-Bell syndrome (Martin & Bell, 1943)" (Folstein SE, Rutter ML (1988) Austism: Familial aggregation and genetic implications. J Autism and Developmental Disorders 18: pp. 16-17)

"Most often, female primates have several males to interact with and choose from, and they most often take advantage of the situation. In groups with multiple males, such as baboons, macaques, and many other primates, females most often copulate with more than one male, and sometimes several in rapid succession. This situation is most apparent in species with breeding seasons, so that several females are in estrus at the same time and no single male can sequester even one female all for himself. Promiscuity, or mating with every possible male, occurs most often when females cycle synchronously. Contrary to what theory suggests, these female primates are not selective and mate with more than one male even when ovulation is imminent." (Small, Meredith F. (1993) Female choices: Sexual behavior of female primates. Cornell Univ. Press, Ithaca, 1993 pp. 135)

"Although measurements of testis size by orchidometry in living subjects are difficult to standardize, they suggest smaller testes in Japanese and Korean men than in Caucasions. Weighing at autopsy is more accurate and showed that the size was twofold lower in two Chinese samples compared with a Danish sample. Differences in body size make only a slight contribution to these values." (Diamond, JM (1986) Variation in human testis size. Nature (London) 320: 488)

"The differences in dizygotic twin frequency, and presumably ovulaton rate, are in the same direction as the differences in testis size. The frequencies of dizygotic twins are even higher (up to 49 per 1,000 births) among African blacks. ... Yoruba women, with the world's highest frequency of dizygotic twins, have higher FSH and LH levels at the time of ovulation than do Japanese women, who have the lowest frequency of dizygotic twins. This variation in female hormone levels may contribute to the distribution of the incidence of breast cancer, which is known to be related to oestrogen levels. Even after all other risk factors for breast cancer have been taken into account, the incidence among Japanese women remains inexplicably low. Perhaps this puzzel, the so-called 'Japanese factor' of (breast cancer, is related to the low double-ovulation frequencies and low hormone levels." Diamond, JM (1986) Variation in human testis size. Nature (London) 320: 488-489)

note:If an inverse relatioship exists between T and sperm production, then a drop in T during prolonged excersise may mean the body is reving up to make more sperm

"One characteristic among primates has been clearly targeted for possible selection by Fisherian female choice--male penis size. Primate males living in groups with many females and many males, groups in which promiscuity is the mating rule, have long penes (Dixon 1978). Male chimps, in fact, use their penes for display toward estrous females. Because a longer penis would give a female pleasure (note that the human male has the longest and thickest penis of any primate), female choice might have been a factor driving penis length to extremes among primates." (Small, Meredith F. (1993) Female choices: Sexual behavior of female primates. Cornell Univ. Press, Ithaca, 1993 pp. 109)

"We conclude that highly trained male athletes, like their female counterparts, may have a deficiency of hypothalamic gonadotropin-releasing hormone. This condition may be caused by the prolonged, repetitive elevations of gonadal steroids and other hormones known to suppress gonadotropin-releasing hormone secretion that are elicited by their daily exercise. [p. 411] Plasm testosterone concentrations increased to a similar extent in the runners and controls. There was no significant difference in either peak testosterone concentrations (12.5 + - 1.19 ng per milliliter in the runners vs. 12.0 + - 1.23 in the controls), area under the curve (576 + - 119 ng per mililiter times hours in the runners vs. 603 + - 92.4 in the controls), or the pattern of testosterone response.[p.413] Plasma testosterone increased significantly from a mean basal value of 5.4 + - 0.5 ng per milliliter to a peak of 8.76 + - 0.66 ng per mililiter 40 minutes after the start of the run, and it remained elevated for the duration of the run. The resting testosterone levels (4.55 + - 0.6 ng per mililiter) were reached by two hours after discontinuation of the exercise. The mean plasma gonadotropin concentrations did not change during or after the two-hour run. There was also no signigicant difference between the luteinizing hormone frequency or amplitude in the entire six-hour period before the run and that in the six-hour period after the run.[p. 413-414] Surprisingly, in spite of these abnormalities, the serum testosterone concentrations in the runners were normal. In contrast, female athletes with hypothalamic amenorrhea have low serum levels of estogen.[p. 414-415] However, profound suppression of testosterone production and of spermatogenesis may occur in men undergoing extremely intense physical training.[414] Similarly, short-term excercise in men not involved in physical training programs was followed by a decrease in levels of plasma gonadotropins and testosterone, thus confirming the suppression effects of exercise on the reproductive system.[p. 416]" (MacConnie, S.E., Barkan, A., Lampman, R.M., Schork, M.A. & Beitins, I.Z. (1986) Decreased hypothalamic gonadotrophin-releasing hormone secretion in male marathon runners. New England Journal of Medicine 315: pp. 411-417)

"More convincing vestiges of a sexual selective history in which females mated polyandrously can be found in the human male. Perhaps the clearest such vestige is testis size (Short, 1977). Men's testes are substantially larger, relative to body size, than those of gorillas, a species in which males are polygynous but females mate monogamously so that "sperm competition" within the female reproductive tract is absent. (goes on to talk of chimpanzees) (Wilson, M., Daly, M. (1992) The man who mistook his wife for a chattel: The Adapted Mind; (Barkow, J.H. & Cosmides, L. & Tooby, J. eds.), Oxford Univ. Press, New York. p. 299)

"Roger Short...had predicted that in {primate} species where females mate with more than one male during a reproductive cycle, the males would have larger testes for their body size than in species whose females had only a single mate per cycle. When the females were promiscous, the sperm of each male would have to compete with those of other males, and the male producing the most sperm was most likely to generate offspring. [quote from] (Harvey and Clutton-Brock 1983, p. 315" (Cronin, Helena (1992) The Ant and the Peacock: Cambridge Univ. Press, Cambridge p. 97)

"Rampant female mating leads to competition not before but after copulation, not among bodies but among sperm. A female copulates with several males whose sperm compete to fertilize her. Sperm competition can occur even if a female copulates with different males several days apart. This is because sperm are hardy and may survive in the vagina of a chimpanzee or woman for as long as eight or nine days. Any female who copulates with more than a single male while ovulating opens the gates to a sperm race. The males or men who produce the sperm are not direct entrants; they are more like corporate sponsors advertising their name and providing financial backing. Not all participants in the all-male marathon are equally prepared to win. Mammals who mate more frequently, and produce more sperm per ejaculation, are more likely to impregnate their partners. Favoring the sperm of one male over that of competitors are such things as position during intercourse, force and timing of pervic thrusting, number and speed to ejaculated sperm, and proximity of the spermatic means of delivery---the penis---to the egg at time of ejacultion. Copious sperm production (estimated by testicle weight), deep penetration, and an elongated penis are all presumably advantages to males engaged in sperm competition. Perhaps most important is sheer sexual vigor, with more active males ejaculating the greatest number of times gaining a competitive edge. The charm and proficiency of a male---his ability to seduce a female and to continue to please after seducing her---of course also crucially determine his chances of entering and therefore of winning the competition; and in this sense females make the great impact of generally deciding who will and will not compete. There is also evidence that a woman who climaxes while making love to her lover is more likely to become pregnant by him." (Margulis, L & Sagan, D. (1991) Mystery Dance, On the Evolution of Human Sexuality: Summit Books, New York pp. 37)

"Large testes and big penises are advantages only under conditions of widespread sexual promiscuity. Among our closest relatives the great apes, only male chimpanzees have testicles more prodigious than those of men. And chimps, with their big, heavy testicles, are more sexually promiscuous than humans. That the sperm-producing organs of chimps and humans are relatively big and heavy strongly suggests that some of our not-so-distant hominid ancestors were far more promiscuous than gorillas and orangutans --- or than many people are today. In the evolutionary past, the competition to reach primate eggs was sometimes between sperm from different male donors. If two or more males copulated with the same female within a period of days, an advantage in begetting offspring accrued to the one who ejaculated the greatest quantity of vigorous sperm cells. Like an auto race won by the driver whose sponsoring company can afford to provide him with the most souped-up car, the male with the best-timed copulation, most far-reaching ejaculation, and biggest testicular "engine" able to produce the greatest quantity of sperm tended to win the "game" of impregnation. Souped-up genitals with a lot of spermatic firepower, like incredibly expensive streamlined racing cars, are worth it only if there is some sort of race or contest. Otherwise they seem expensive." (Margulis, L & Sagan, D. (1991) Mystery Dance, On the Evolution of Human Sexuality: Summit Books, New York pp. 33)

"But although silver foxes had been bred in captivity since 1892 on fur farms, and although some selective breeding for traits such as fertility and high fur quality had been practiced, the animals were not domesticated in any strict sense. They retained all of the essential characteristics of their wild counterparts. They molted and came into heat in a strict seasonal cycle, as in the wild; their behavior toward humans was no different than that of a wild fox raised in captivity. So Belyaev decided to try an experiment. He would rigorously select animals applying but a single criterion: Those animals that showed consistently tame behavior toward humans would be kept; those that did not would be eliminated from the breeding program. Within five generations changes were already apparent. By 1979, twenty years into the experiment, the results were astonishing. His tame-selected foxes were not just tame; they acted for all the world like domestic dogs. They approached familiar persons and licked their hands and faces. They barked like dogs. They even sought the attention of strangers by whinning and wagging their tails. Their annual molting cycle was disrupted, and the females began to come into heat twice a year, like dogs, and unlike both foxes and wolves. They also developed some physical characteristics of young foxes, such as drooping ears, and some of the variations in traits seen in other domesticated animals, such as piebald coat coloration." (Budiansky 1992: 96, The Covenant of the Wild)

"Status and the ranking of males in the hierarchy of dominance seems to be far more important, in chimpanzee society, than erotic drives. In chimpanzee culture, male dominance is not a means for monopolizing a harem of females, and since paternity is not in evidence, it would seem also that male dominace is not a means of ensuring inculsive fitness; rather, Lawick-Goodall has observed that the ranking is a means of preserving the social band." (Thompson, W.I. (1981) The Time Falling Bodies Take To Light; St. Martin’s Press: New York p. 66)

"For the first two years of his reign Figan held a position of almost absolute power in the community. This meant that he could, if he so wished, maintain all but exclusive mating rights over any female who caught his fancy. Once he had proclaimed his interest by threatening any would-be suitors who approached too closely, his mere presence, close to the lady friend of the moment, was usually sufficient to inhibit the sexual advances of the other males. He established a pattern, taking over the community females, one after the other, when they were at their most alluring --- during the last four or five days of their swellings. Faben's privileged position was very apparent at such times for Figan usually shared his sexual possesions with his brother much as he shared precious food items, such as meat." (Goodall, Jane (1990) through A Window. Houghton Mifflin: Boston p. 55)

"I had been unaware that the "challenge" display to two adult, rival gorillas incorporated lacertilian features until Dian Fossey presented a seminar at our laboratory and acted out what she refers to as the "parallel display of two silverbacks. When she mimicked their sideways presentation and their walking with stilted, awkward steps, I was immediately reminded of the close-in desplay of certain lizards (Chapters 6-9). The so-called parallel display of gorillas has been earlier referred to by Schaller as the "stutting walk." Phrased in his words, the gorilla displays the side of the body; the arms are bent outward at the elbow, giving them a curious curved appearance and making the hair on the forearm look impressive; the body is held very stiff and erect, the steps are short and abrupt, and except for brief glances, the head is turned slightly away form the opponent. Reminiscent of voiceless lizards, the silverbacks that strut within 10 feet of each other utter no vocalizations during the display. A similar strutting walk is seen in courtship." (MacLean 1990: p. 232 The Triune Brain in Evolution)

"Conflict with parental care: In many avian species, males provide significant parental care, resulting in marked increases in reproductive success. Evidence is mounting that high plasma levels of testosterone interfere with expression of parental care in males, resulting in reduced reproductive success. (Wingfield, J.C., Jacobs, J. & Hillgarth, N. (1997) Ecological constraints and the evolution of hormone-behavior interrelationships. Annals of the N. Y. Academy of Science 807: pp. 34)

"Postulated functions for this neophilia include avoiding inbreeding and maximizing the genetic diversity of offspring (Small, 1993), and inducing paternal uncertainty to protect infants against infanticide by males (Hrdy, 1981). But among primate species, intense neophilia and female promiscuity seems to correlate with intense sperm competition. Perhaps neophilia also maximizes sperm competition, particularly between known and unknown males. Under condiditions of "runaway sperm competition", neophilia and female promiscuity, combined with elaborated estral swellings, facilitate sperm competition within female reproductive tract around the time of ovulation, thereby increasing the likelihood of females having male offspring with large testicles, high sperm counts, and high sperm motility. This pattern of runaway sperm competition seems to have occured among the common chimpanzees and pygmy chimpanzees. Because there is an inherent trade-off between behavioral female choice for individual male traits, and 'physiological female choice' for the best sperm (which required mating indiscriminately with as many males as possible, to maximize the sample size of sperm donors), female chimpanzees are surprisingly non-choosy for primates of their social intelligence. However, given female neophilia in favor of new males, males capable of displaying novel and unexpected behaviors may gain an advantage through exploiting neophilia as a perceptual bias (Ryan, 1990). In our ancestors, neophilia at the level of preferring new individuals could have then shifted towards neophilia at the level of preferring new behaviors by known individuals. Runaway sperm competition turned into runaway brain evolution among our ancestors. This shift may explain the great differences between chimpanzee and human mental capacities and mating patterns." (Miller, Geoffrey F. (1994) Evolution of the human brain through runaway sexual selection: the mind as a protean courtship device. unpublished thesis. pp. 381-2)

"White and Chapman found that chimpanzee females tend to move apart whenever they find themselves near one another, whereas in bonobos it is the males who stay away from one another. All other sex combinations show tolerance and cohesion---that is, individuals remain together once they have gotten close. This suggests that the chief difference is between male bonding and female aversion in the chimpanzee and female bonding and male aversion in the bonobo. The data of Furuichi and Ihobe from Wamba, however, provide a slightly different picture. They, too, found high affiliation among female bonobos, but further report that males of this species travel together and groom one another just as much as male chimpanzees in Mahale do." (De Wall & Lanting 1997: 65, Bonobo)

"The one consistent species difference is a closer relationship between the sexes in bonobos. At Wamba, three-quarters of the traveling parties are mixed: they include adults of both sexes and mothers with offspring. The figure for Lomako is only slightly lower. At both study sites, grooming (a widely accepted guage of social ties) is most common between the sexes, followed by grooming among females, with the least amount of grooming among males. In the chimpanzee, males will travel with a sexually receptive female, but since females are only occasionlly in this attractive state, the sexes rarely seek each other's company. Female bonobos, on the other hand, sport the pink swellings that signal receptivity for extended periods of time; parties virtually always include at least one swollen female. Perhaps as a result, the sexes are more often together in mixed companies. Furthermore, male bonobos---including fully grown ones---follow their mothers around through the forest, which makes for even more intersexual association. Since females of both species migrate to other groups, the only close kinship ties that get a chance to form are those between mother and son and between brothers (fatherhood is unknown to the investigators and almost certainly to the apes as well.) Chimpanzee brothers tend to associate and support each other in fights, such as the alliance between Faben and Figan that allowed Figan to conquer the top spot in the Gombe community. In contrast, the mother-son bond in chimpanzees, although clearly in evidence, is only minimally developed. Bonobos show the opposite pattern: the focus of male kinship bonding has shifted from siblings towards the mother. That the mother son tie also has implications for the male rank order makes the parallels and contrasts with chimpanzees all the more intriguing." (De Wall & Lanting 1997: 67, Bonobo)

"The conclusion I am forming is that the peculiarly human female constant availability for sex and the peculiar highly socialized, promiscous human male are both results of the high selective value in hominid evolution of a non-aggressive male."

"Among males the situation is entirely different. As far as we know, males do not move between groups, and dominance seems to matter a great deal to them. There is much more fighting among males than among females. Whereas rank positions near the top, specifically the position of alpha male, tend to be quite clear, mid-ranking and lower positions are not so well defined. Since bonobos do not show elaborate status rituals, the rank order is mostly expressed in the direction of aggressive chases. These encounters, which rarely escalate, often end in a quick conciliatory contact in which two males mount each other or rub their scrotums together standing back-to-back. (De Wall & Lanting 1997: 74, Bonobo)

"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 & Lanting 1997: 76, Bonobo)

"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 remales 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 & Lanting 1997: 78, Bonobo)

"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 & Lanting 1997: 107, Bonobo

Bonobo life stage chart says Nursing period 0-5, First genital swelling (onset of adolescence) 7, Begins to wander between groups 8, Settles into new group 9-13, Menarche and first full-sized swelling 10, Growth-cessation (adult size reached) 14-16, First offspring 13-15, Cessation of ovulation (menopause) 40, Longevity 50-55. (De Wall & Lanting 1997: 190, Bonobo)

"It is tempting to speculate that bonobos are flooded with oxytocin. This mammalian hormone promotes the mother-offspring bond. Oxytocin is released during birth and in nursing females; its original function is to trigger muscle contractions necessary for parturition and lactation. When it reaches the brain, however, the hormone seems to serve a broader function. In rodents, oxytocin has been found to stimulate affectionate behavior and, in turn, to be released as a result of that behavior. (Insel 1992). If oxytocin indeed circulates in large quantities in the blood of bonobos---a testable hypothesis---this might explain their high level of social and sexual bonding. That possibility is not, however, an alternative to the evolutionary scenarios discussed in chapter 5. If bonobos have physiological mechanisms that make them seek intensive contact, and that perhaps provide them with satisfaction from such contact, the question of how these mechanisms evolved still remains. It is generally assumed that natural selection "attaches" rewarding experiences to particular kinds of behavior so as to urge animals to do what is best for them." (De Wall & Lanting 1997: 192, Bonobo)

"One of the most curious results to come out of bird studies in recent years had been the discovery that "attractive" males make inattentive fathers." (Ridley 1993: 224, The Red Queen)

"We have heard, but have been unable to verify, that undescended testes are common in autistic children." (Geschwind & Galaburda 1987: 173, Cerebral Lateralization

"When gonadectomized males were treated with testosterone, however, they became more aggresive to subordinate males but not to more dominant males or females. Factors such as physical condition and previous social experience may be more important than gonadal hormones in influencing aggresive interactions in these captive groups of talapoins." (Dixon, A. & Herbert, J. (1977) Testosterone, Aggressive Behavior and Dominance Rank in Captive Adult Male Talapoin Monkeys Physiology and Behavior 18: pp. 539)

"All aggresion was directed towards lower ranking males, however, and no animal rose in rank after hormone therapy. All four males showed increased threats and three showed increased attacks towards subordinate males, whilst male 1017 showed small decrease in the frequency of his attack behavior. ... When gonadectomized males were treated with testosterone, they became more aggressive towards lower ranking males but not towards dominant males or females. No male rose in the hierarchy as a result of testosterone therapy. The high dose of testosterone produced supra normal levels of hormone in the plasma of gonadectomized males, but there were no further changes in their aggressive behavior." (Dixon, A. & Herbert, J. (1977) Testosterone, Aggressive Behavior and Dominance Rank in Captive Adult Male Talapoin Monkeys Physiology and Behavior 18: pp. 542)

"The male contribution to fertility is also affected by starvation. In young American men who volunteered to undergo experimental starvation, sperm were fewer, less motile, and shorter-lived than normal (Klatskin et al. 1947, cited in Stein and Sausser 1975). High temperatures and high altitudes also tend to produce aspermia (Cowgill 1969). (Bernds, W.P. & Barash, D.P. (1979) Early Termination of Parental Investment in Mammals, Including Humans In Evolutionary Biology and Human Social Behavior. N. Chagnon & W. Irons, eds. Pp. 495)

"It is also now clear that high plasma levels of testosterone are immunosuppressive (fig 2). This may have first arisen as a mechanism to suppress actions of the immune system within the testes, because as developing spermatozoa become haploid, they develop surface proteins that are recognized as foreign by cells of the immune system. Thus, suppression of immune responses within the testes enhances fertility. Problems arise when testosterone is secreted into the blood and then has the potential to inhibit the immnune system throughout the organism." (Wingfield, J.C., Jacobs, J. & Hillgarth, N. (1997) Ecological constraints and the evolution of hormone-behavior interrelationships. Annals of the N. Y. Academy of Science 807: pp. 25)

"Conflict with parental care: In many avian species, males provide significant parental care, resulting in marked increases in reproductive success. Evidence is mounting that high plasma levels of testosterone interfere with expression of parental care in males, resulting in reduced reproductive success. (Wingfield, J.C., Jacobs, J. & Hillgarth, N. (1997) Ecological constraints and the evolution of hormone-behavior interrelationships. Annals of the N. Y. Academy of Science 807: pp. 34)

"Barbary macaques have been of special interest to primatologists because of two interesting features. Females mate with almost all available males in the group, and yet males interact extensively with infants. In other words, males interact with infants that may not be their own. Based on observations of two separate colonies of provisioned animals, Kuester and Paul (1984) and Small (in press, b) have provided detailed descriptions of the mating patterns of female Barbary macaques. Females breed in the fall and undergo an average of 2 cycles. They exhibit extreme swelling and color changes of the perineal area that can last several weeks. Detumescence is rapid, and is followed by visible menstruation 14 days later. The second cycle is often less physiologically intense, although it may not be so behaviorally. In addition, females have a second or third estrus even if they are pregnant and solicit males at the usual rate. The most remarkable feature of Barbary macaque mating is the frequency of copulations and the number of partners. Small (in press, b) calculated an average of 2.23 copulations per hour with an average of 7 different partners during each estrus (range 1-14). Small also observed one female who copulated with 3 different males in 6 minutes. Taub (1980a) used the euphemism "consociation" in an attempt to gain some respectability for female Barbary macaque "promiscuity." In fact, females rarely stay more than a few minutes with any male, and move form partner to partner while the males seem unable to stop them (Small, in press, b). In captivity and in the field, these are the most sexually assertive of females macaques, and they seem to play the major role in determining mate with whom, and when. .... Males are somewhat related, and they also are not extensively dimorphic in size from females." (Small, Meredith F. (1989) Female choice in nonhuman primates. Yearbook of Physical Anthropology 32: pp. 119-120)

"Boinski (1987) conducted the first field study of squirrel monkeys in which individual animals were recognized. Squirrel monkeys live in medium to large multi-male/multi-female groups )approximately 35 individuals in Boinski's study), and they are exclusively arboreal. Boinski was able to determine that females, not males, transfer between groups, That there is little male-male aggression and no discernible male hierarchy. Females are seasonally receptive and each estrus lasts only 6-8 days. Male squirrel monkeys increase in size by 20% during the breeding season. More signigicantly, Boinski determined that the largest male is responsible for 70% of the observed copulations. Females actively and assertively solicit copulations. They engage in mutal olfactory investigations with males and place their hindquarters up to the nose of males. Females apparently prefer the largest male, but when he was ocupied, or did not respond, they copulated with other males." (Small, Meredith F. (1989) Female choice in nonhuman primates. Yearbook of Physical Anthropology 32: pp. 114)

"Nevertheless, castrated tomcats live longer than their intact male counterparts, and so do human castrates. Detailed comparisons standardized for age, intelligence, and category of mental deficiency among castrated and intact inmates of a mental institutution in Kansas demonstrated that the median age at death of intact men was 55.7 years, as compared to 69.3 years of castrates, and that the earlier the castration was performed, the more life expectancy was increased." (Badcock, C. (1991) Evolution and Individual Behavior: An Introduction to Human Sociobiology Oxford: Blackwell. pp. 14)

"For instance, one known effect of testosterone is to raise the resting metabolic rate of males by approximately 5 percent as compared to females. Effectively, this means tht the male biochemical "engine" is running about one-twentieth faster all the time than is that of a woman, perhaps explaining why it wears out sooner." (Badcock, C. (1991) Evolution and Individual Behavior: An Introduction to Human Sociobiology Oxford: Blackwell. pp. 15)

"...human testis size falls right in the middle of the range for ground-dwelling polygynous primates such as gelada and hamadryas baboons, which suggests that like them and like gorillas, human males are not as adapted for easy going promiscuity as some earlier enthusiasts for the chimpanzee model of human adaptations may have wished." (Badcock, C. (1991) Evolution and Individual Behavior: An Introduction to Human Sociobiology Oxford: Blackwell. pp. 149)

Sandor and Mehdi (1979) postulated that steroids are very ancient biomolecules which evolved prior to the origin of eukaryotes and were even synthesized abiotically." (Matsuda, Ryuichi (1987) Animal Evolution in Changing Environments, with Special Reference to Abnormal Metamorphosis. N.Y.: Wiley Press pp.9)

"The serum levels of estradiol (E2) and testosterone (T), the metabolic clearance rates of estradiol (MCRE2) and testosterone (MCRT), and the production rates of estradiol and testosterone (PRE2) and (PRT) were examined in 22 male smokers and 21 male nonsmokers. Seminal fluid indexes (sperm count, % motility, grade of motility, and % of sperm with abnormal morphology) were also assessed. The mean E2 level and the mean PRE2 were significantly greater in smokers than in nonsmokers (P less than 0.001 and P less than 0.01, respectively); however, the means of MCRE2, MCRT, PRT, and T did not differ significantly in smokers compared to nonsmokers. No significant product-moment correlations were found between the various hormonal measures and the seminal fluid indexes in the overall sample. However, the smokers with sperm counts below the median sperm count of the sample had significantly higher mean levels of E2 and PRE2 than did the smokers with sperm counts above that median. Mechanisms that might mediate the greater PRE2 of smokers and a negative relationship between estradiol and sperm count are discussed." (Klaiber EL, Broverman DM (1988) Dynamics of estradiol and testosterone and seminal fluid indexes in smokers and nonsmokers. Fertil Steril 1988 Oct;50(4): 630-634)

Summary

These excerpts form the background for an hypothesis that suggests that there is an inverse relationship between increased testosterone in the males of primate species, including humans, and a decrease in sperm production. Relatively non-hierarchically organized males competing for mates in a promiscuous social structure, would be selected for increased sperm production (larger testicles) while at the same time those males with lower testosterone levels would be more likely to fair well in a cooperative social environment characterized by less hierarchical posturing.

Female sexual selection could have powerful consequences when paired with the selection of non-aggressive, large testicled (high sperm count) males -- animal or human societies more likely to be matrifocal.

Females choosing males for tendencies toward cooperative behavior and tolerance for infants ---females choosing males for the hormonal constellation characterized by lower testosterone -- would be at the same time picking those males likely to produce more sperm making these males likely successes in a promiscuous social structure.

Females choosing males for this constellation of features; low testosterone, high sperm counts, cooperative social behaviors, are selecting males who are maturationally delayed; displaying neoteny or a prolongation of infant characteristics into adulthood relative to their genetic ancestors.

Social structures reinforcing the benefits that come with a hierarchial orientation, for example a harem, would evidence males with relatively low sperm counts (smaller testicles) and increased aggressive tendencies associated with higher testosterone levels. These males could evidence maturational acceleration relative to their ancestors. A harem social structure (in the case of humans, a patriarchal social stucture) would reinforce a male hormonal constellation characterized by aggression, hierarchical posturing, low sperm counts, and non-cooperative behavior evident in maturational acceleration.

We hypothesize that increasing sperm counts decreases testosterone levels and visa versa. At the same time decreasing sperm counts will increase testosterone levels and the reverse.