سؤال يتعلق بجماعة الجنس الثالث .
يتم تعريبSpecies وSexإلى جنس, ليحدث تشوش في المفاهيم وينقسم جنس البشر الواحد إلى عدة أجناس على أساس الهوية الجنسية! تسمى المرأة (الجنس الآخر ) كأنها إضافة إلى جنس البشر- الذكور حكماً!
إي المهم,هذا مقطع من مقال علمي لحد - بالإنكليزية للأسف- يتناول الموضوع من ناحية قد تقارب موضوع التساؤل, مرفق المقال بأكمله وهو عرض للأبحاث ليس مغرقاُ يالتعابير الطبية الاختصاصية-
Biomedical research into transsexualism and
homosexuality
The leading principle into the biomedical research of
homosexuality/transsexualism has been to identify biological
female traits in male-to-female transsexuals and male homosexuals
and male biological traits in female-to-male transsexuals
and female homosexuals. Not stated explicitly, the paradigm in
this type of research is that expressions of sexuality, such as
transsexualism and homosexuality, are variations on the fundamentals
of male/female dichotomy and heterosexual interaction
(Gorman, 1994). Some researchers do not differentiate
between homosexuality and transsexualism, viewing them as
evidence of femininity in males and of masculinity in females.
This approach is flawed and lacks thorough enquiry into the
matter, since the two behaviors are fundamentally different.
Transsexuals' deepest desire is to become members of the
opposite sex and their expressions of cross-gender behavior are
serious attempts to live the life of the desired sex. The desire to
become a member of the opposite sex is alien to homosexuals
and the effeminacy of some homosexuals is not rarely a caricature
of women's manners, sometimes acted out only in the
company of peers and not in other contexts. To the best of my
knowledge the assumption of female traits in male homosexuals
and, vice versa, of male traits in female homosexuals has been
made at face value and its validity to guide biomedical research
may be questioned. This issue has been reviewed recently
finding large degrees of fluidity in populations and eras
(Sandfort, 2005). To regard a subset of male-to-female transsexuals
as feminine homosexuals (Blanchard et al., 1987) is in
my view erroneous. The very definition of homosexuality states
that there is mutual pleasure from having intercourse with a
person with the same body/genital morphology. A preoperative
transsexual having intercourse with a man could, at first sight, be
labeled as homosexual, but a major obstacle to labeling it as
homosexual is that the transsexual does not derive pleasure from
the arousal of the male genitalia as true homosexual men do,
rather the contrary: this type of sexual encounters reaffirms the
alienation from the male sexual anatomy that male-to-female
transsexuals experience. In my clinical experience male-tofemale
transsexuals find sexual encounters with homosexual
men not complementary to their sexual imagery, and vice versa.
Sexual interest in and sexual interaction with members of the
opposite sex (heterosexuality) are the statistical norm, and the
desire of a man for sexual interaction with another man, has
been, to fit the heterosexual model, viewed as a manifestation of
a female brain differentiation (and of a male brain differentiation
in lesbians). For its theoretical foundation animal experimentation
has been widely used, to test whether animals with a male
anatomy could be hormonally manipulated to sexually interact
with a male. And indeed this has been possible (Baum et al.,
1990; Paredes and Baum, 1995) (see accompanying paper by
Michael Baum with a review of his own and others' work). The
eminent animal researcher Beach (1978) has reviewed the
importance and relevance of animal models for sexology to the
human species. Beach has remarked that the term homosexual in
animal research has been used in two different contexts (1) as a
description of individuals that exhibit a coital pattern typical of
the opposite sex and (2) as a description of individuals that
exhibit coital responses typical of their genetic sex but do so in
response to like-sexed partner. Beach further noted that,
particularly in the study of lower mammals, there is a mutually
exclusive and inflexible separation of the copulatory motor
patterns of males and females. Mounting and pelvic thrusting are
usually viewed as exclusively male patterns, presupposing a
male brain organization, whereas lordosis and reception of
mounting and intromission are considered female patterns,
presupposing a female brain organization. In some research male
homosexual behavior is viewed as receiving intromission of one
male (female brain organization?) from another male (with a
male brain organization?) The alleged brain organization of the
latter male is often not well defined. As an inserter this person
would qualify for a male brain organization but yet must be
viewed as homosexual because he interacts with another male.
Suffice it to say that sexual activity of the human species (both
heterosexual and homosexual) is less mechanistic and robot-like
than the above described copulatory patterns. Copulatory
patterns and associated eroto-sexual behavior is fluid and
flexible to an extent which is not observed in animal experimentation
of lower mammals but demonstrable in primates
(Wallen, 2005). And more specific for homosexuals, the insertor
may become the insertee and vice versa.
A remarkable finding in animal research has been that
olfactory clues play a significant role in seeking out sexual
partners of the opposite sex (Kelliher and Baum, 2001; Paredes
and Baum, 1995). Whether these olfactory clues have a
counterpart in the human with regard to partner selection has
not been thoroughly investigated but is addressed by Michael
Baum in his contribution. The a priori likelihood is, however,
limited. Compared to most animal species, olfactory capacity of
the human species is limited. Further, the present western culture
Impact of hormones on gender identity/sexual orientation.
Lessons from clinical syndromes
Sexual differentiation begins with the sex difference of the
chromosomes established at conception. In humans, no evidence
can be found that the combination of chromosomes present in all
cells (normal: XY, XX, or abnormal: XXY, XYY, XO etcetera)
of the body has a direct effect on gender identity or sexual
orientation. Rather, the influence is indirect and derivative
through determination of the nature of the embryonic gonadal
anlagen and their hormonal products (Gooren, 1990; Hughes,
2001; Migeon and Wisniewski, 2000, 2003; Money, 1981).
In the mid-1900s, it became clear from animal experimentation
that the process of sexual differentiation is not completed
with formation of the external genitalia but that the brain, as
substrate of sexual and nonsexual behavior, also undergoes
sexual differentiation to match the other characteristics of sex.
In lower animals, evidence has accumulated that the same
hormonal organizing principles of sexual dimorphic differentiation
account for both the genitalia and the brain (Gorski, 2002;
Hughes, 2001; Migeon and Wisniewski, 2000, 2003; Swaab et
al., 2002). This hormonal action of testosterone has been termed
organizational, and it is exerted during a rather circumscribed,
so-called critical period of prenatal or early postnatal development.
In some species of lower mammals part of this action,
particularly the defeminization, is mediated by estrogens
through aromatization of testosterone. The issue of defeminization
by estrogens is addressed by Michael Baum in his twin
paper in this volume and in Baum (2003) and McEwen (2001)
but estrogen-driven defeminization does not occur in primates
and the human, as became apparent from men who have a
estrogen receptor defect or an aromatase deficiency, and,
therefore, have lacked a normal estrogen stimulus prenatally or
postnatally (Rochira et al., 2002).
The main regions of the mammalian brain involved in sexual
differentiation are the hypothalamus, the septum, the bed
nucleus of the stria terminalis, the preoptic area, and the
amygdala (Gorski, 2002; McEwen, 2001; Swaab et al., 2002).
The sexual dimorphic differentiation of the human brain is less
well documented, but a number of sexual dimorphic nuclei have
been found (sexual dimorphic nucleus (SDN) and the bed
nucleus of the stria terminalis (Gorski, 2002; Swaab et al., 2002).
The morphologic sex difference in the SDN is not established
until the first postnatal years following a period there are no
significant sex differences in circulating sex steroids; and the sex
difference of the bed nucleus of the stria terminalis appears only
in adulthood (Swaab et al., 2002). While the mechanism of
sexual differentiation in laboratory animals is clearly orchestrated
by gonadal steroids (Gorski, 2002; Swaab et al., 2002)
and maybe also genetic factors (Tobet, 2002), in humans the
mechanism of brain sexual dimorphism (hormonally determined
or not) and the clinical relevance are not yet certain. In humans
this information is to be obtained from “experiments of nature”:
genetic and endocrine disorders that spontaneously occur in the
fetus or result from exposure to exogenous hormone or
estrogenic drugs during pregnancy (Gooren, 1990; Migeon
and Wisniewski, 2000, 2003; Money, 1981). But the brains of
subjects suffering from these conditions have not been studied.
But overall, clinical observations support the hypothesis that in
human prenatal development, sexual brain differentiation is
subject to effects of androgens, but these are not of the hormonalrobot
type found in subprimate mammals, in which sex steroids,
in the set of behaviors studied, typically exert a simple on–off
effect on sexual functioning, both in their organizational and
activational effects (Gooren, 1990; Migeon and Wisniewski,
2000, 2003; Money, 1981), and there are certainly other
unidentified factors that modulate or override androgen effects
on the central nervous system. For instance, male and female
cells differ because of differential effects of sex chromosome
L. Gooren / Hormones and Behavior 50 (2006) 589–601 593
|
بحث
قائمة الأعضاء
التقويم
وثائق المساعدة
/
سؤال يتعلق بجماعة الجنس الثالث .
