It is also a popular assumption that only hormones influence sexual behavior, when in reality research has revealed that often the environment, both physical and social, affects the secretion and production of hormones. Often, only an environmental cue is necessary to initiate behavior that leads to nesting and reproduction in some species of birds. The zebra finch of Australia, for example, occupies one of the harshest habitats on earth, with droughts lasting as long as three years. Both female and male zebra finches are in a state of reproductive readiness during these arid months, with developed ova and sperm, and begin mating within 10 minutes of the long awaited rain. The finch then proceeds to nest building and egg laying within a week (Arnold, 1975).
There is strong evidence to suggest that environmental factors affect hormonal levels in animals. External environmental factors can produce changes in hormonal levels and reproductive rhythms. Auditory stimuli provide one such example. When laboratory rats were exposed to one minute intervals of bell ringing every 10 minutes around the clock (Zondek & Tamari, 1967), the effect was associated with increased production of germ cells in both males and females, increased organ weight for uterus and ovaries, and prolonged estrous. It has also been established that for ferrets light has some similar effects (Donovan, 1967). The social environment also can have profound effects on reproduction in laboratory animals. For example, male rats housed in isolated individual cages exhibited lower levels of plasma testosterone than those housed in groups (Dessi-Fulgheri, Lupo di Prisco, &. Verdarelli, 1976). The mere lack of exposure of male to female rats has resulted in impaired testicular function compared with socially active rats (Jean-Faucher, Berger, De Turkheim, Veyssiere, & Jean, 1978). Overcrowding can have an effect on animal reproduction as well, resulting in lower ovulation rates among free-ranging rabbits (Lloyd, 1967). Such synchrony of biology and environment clearly has survival value, but in these cases it is the environment that is the controlling factor.
In non-human primates, a rise in social status precipitates a rise in plasma testosterone levels, as in the rhesus monkey (Mazur, 1976; Rose, Bernstein, & Gordon, 1975). A similar phenomenon has been observed in humans. A study of male tennis players linked mood, changes in social status, and subsequent changes in hormone levels (Mazur & Lamb, 1980). The change in testosterone levels from pretest to posttest was examined in relation to their having been victorious, or having lost (presumably affecting mood). In decisive tennis matches, winners showed significantly more increase in testosterone than did losers. No difference was found in players who simply were designated as winners of a lottery style contest with identical rewards. The results imply that the fluctuations in testosterone were tied to some effort on the part of the victors, but more important to our discussion, the results also suggest two other important processes. First, simply having won a contest may increase testosterone. Elevated levels of testosterone do not necessarily increase performance, but perhaps it is performance that increases (or decreases) testosterone. Second, it is possible that increased levels of plasma testosterone may not put men “in the mood,” and perhaps being in the mood elevates testosterone. Clearly the direction of influence is arguable, and the simplistic notion that our hormones elicit natural behavior (including promiscuity in males for example) is misguided. This is especially important considering the vast opportunities for change in social status, and as well as mood changes, in the daily life of our culture. It also clearly suggests that cultural determinants play a vital role in our behavior whether it be competitive or sexual.
The human body is indeed a sophisticated system. Minor hormonal influences can affect the sexual phenotype greatly, but the environment, especially with regard to the gender role in which one is immersed, can have a perhaps greater impact than simple biology. That is, the social definitions and expectations of others can elicit behavior and personal styles that are generally consistent with those expectations, even when chromosomal makeup is at variance with the imposed social definitions. In one case, a genetic female with male external genitalia, internally possessing a uterus, fallopian tubes, and partially developed ovaries, was raised as a boy (Money, Hampson, & Hampson, 1955). The young man eventually had operations to remove the internal female reproductive organs, but the memorable aspect of this example is the determination with which as a young adult he would pursue his established gender role. At the time of his first contact with the authors he had met and fallen in love with the young girl who would one day be his wife, and was determined to be married to her despite facing repeated operations to correct his underdeveloped penis, along with the maintenance of male hormone therapy. Even though this young man sometimes experienced concern over his apparent differences throughout his childhood (as when he began to develop breasts), and was aware of the removal of female structures, his male role was well established. When he was at college, a homosexual advance by another young man, made him, by his own report, nauseated. He had always known that he wanted to be married someday; he later married a young woman and they conceived children by artificial insemination.