Bisexuality

BISEXUALITY (from Latin bis- twice and sexus- sex), the simultaneous presence in normally separate-sexed animals, including humans, of dependent sexual characteristics of both male and female. Dependent (eusexual) sexual characteristics are those that require for their development the hormones (secretions) of the gonads, in contrast to independent (pseudosexual) and somosexual secondary sexual characteristics, which develop without the participation of sex hormones (see Sexual characteristics). The manifestations of B. can be very diverse. In some cases, B. manifests in humans and animals only in the form of attraction to both male and female sexes, despite the correct development of physical sexual characteristics of only one sex (male or female); in other cases, along with bisexual attraction, the bisexual individual also possesses physical characteristics of both sexes (see Hermaphroditism). The complex and sometimes very confusing manifestations of B., with mosaic development of male and female characteristics, find explanation in a number of experimental studies: in mammals (Steinach and others), birds (Pézard, M. Zavadovsky and others), amphibians (Breslau, Harms and others). Steinach transplanted ovaries to normal male rats and guinea pigs, and as a result observed in such individuals the alternating manifestation of either male or female sexual instinct. Such individuals alternated courting females and behaving in the presence of a male as females. Females with transplanted testes also exhibited bisexual behavior. Zavadovsky obtained similar results in chickens. In experimentally obtained bisexual individuals, along with the alternating manifestation of either male or female instinct, the physical eusexual characteristics of both male and female develop in a complex mosaic combination. In a chicken, for example, along with female-type plumage, male-type crest and voice may develop. One should distinguish between active and latent, or potential, B. Active B. can be called those cases where the dependent sexual characteristics of both sexes are already expressed in one or the other individual. Latent, or potential, B. should be called those cases where the organism, without transplantation of a gonad of the opposite sex, is capable under certain conditions of developing the characteristics of the opposite sex. Zavadovsky showed that in this sense any chicken is potentially bisexual, because removal of its only left ovary inevitably leads to the development on the right side of a testis-like gland. The testicular gland that develops under these conditions causes the development of male dependent sexual characteristics. In a number of cases, spermatozoa developed in such a gland. There is reason to believe that the females of many birds, like the chicken, are potentially bisexual. But there is no sufficient basis to extend this concept of the bisexual nature of the female bird to mammals. B. should not be confused with hermaphroditism (see). Hermaphrodites are animals and humans in which, along with the characteristics of one sex, the characteristics of the other sex are also developed. In everyday life, attention is usually paid to the external parts of the genital passages; but a biologist with equal right calls a hermaphrodite both a goat that has an underdeveloped penis along with a vaginal slit, and a chicken that crows like a rooster and has put on a rooster's plumage. Thus, a hermaphrodite is called an animal with any sexual characteristics of the opposite sex. A bisexual animal should be called only one that, along with the gonads of its own sex, carries gonads of the opposite sex; it makes no difference whether the gonads of the opposite sex have a normal or abnormal appearance and structure. What is essential is not the morphological structure, but the ability to secrete sex hormones. A bisexual animal should thus be called one in whose body tissues that produce male and female sex hormones are functioning or are in a latent state. The presence of sex hormones can be judged by the development of the corresponding, hormone-dependent, characteristics. Thus, if all secondary sexual characteristics developed with the participation of sex hormones, the concepts of hermaphroditism and B. would coincide. But, in reality, not all secondary sexual characteristics require the participation of a sex hormone for their development.