lpetrich

There are several issues that tend to get mixed up here.

Gender identity. We have a strong tendency to perceive ourselves as belonging to one of the sexes. However, this identification sometimes does not work properly.

Physical features. There are noticeable differences between the sexes, though these are all the result of relative growth rates -- some parts grow bigger than others. Some "differences", however, are purely cultural -- both sexes have scalp hair that grows at the same rate, though women usually let it grow longer than men do.

Mental features. This is rather controversial. But though there is some evidence of difference, there is often a good deal of overlap, and the sexes are sometimes difficult to distinguish. For example, there is no such thing as "male grammar" vs. "female grammar".

I think that the differences get exaggerated or noticed more as a side effect of gender identity ("women are from venus, men are from mars").

The occurrence of lookalike sexes may seem farfetched, but it is common among protists, algae, and fungi, where it is called "isogamy". Some of them have more than two sexes -- some basidiomycete fungi have thousands of them ("mating types"). They don't need a member of every sex to be present to reproduce sexually; just members of two different ones.

Nostalgic Pushhead

Wow, I completely forgot about gender identity. Got lost in the shuffle somewhere...
That concept explains everything.
Now... where does it come from?

(Busy studying, can't write another unintelligable 300 word post on the subject, sorry)

ps418

First, no sex or gender is superior in any general way. To assert otherwise is simply to reveal one's own sexist biases.

Second, it should be obvious that hormones play a profound role in producing the physiological sexual differentiation of all mammals, including H. sapiens and their brains. Hormones also play a profound role in the regulation of all sorts of behaviors, particularly those behaviors that differ greatly on average between males and females, such as aggressiveness. Hormonal differences therefore are a strong "biological" component of sex-differences in behavior. See the journal Hormones and Behavior.

In humans, sexual differentiation occurs because men's Y chromosome carries a gene, known as the testis-determining factor, a transcription factor which causes the development of testis, which in turn greatly elevates plasma androgen levels, which in turn produce the male-typical physiological and behavioral patterns. So, there is no doubt that a genetic difference between males and females -the presence of absence of the TDF gene-- is a "biological factor"accounting to some extent for their behavioral differences.

It is also likely that the TDF plays a more direct role in producing between-sex brain and behavior differences, a role that is not mediated indirectly by gonad-produced androgens. Such a direct effect of sex-determing genes on brain and behavior has been demonstrated in mice, for example (De Vries et al, 2002).

There is plenty of evidence that hormonal differences, both in utero and later in life, contribute to the average between-sex differences in some cognitive abilities. Though men and woman are equally intelligent (total IQ), their profiles of average strengths and weaknesses are not the same. For example, on average woman have better verbal memory, whereas men on average have better spatial abilities (e.g. spatial rotation tasks).

That these average differences are related to hormonal mechanisms is supported by a variety of evidence, including the fact that variations in these specific abilities are associated with natural hormone level variations in women, and by the studies which look at the effect of administered hormones on cognitive functioning. See Doreen Kimura's homepage, as well as Kimura (1999a,b; 2002). Kimura (1999a, p. 123) writes:


Fetal excess exposure to androgens can also produce permanent behavioral changes, even without postnatal excess androgens. To take one illustrative example, girls born with congenital adrenal hyperplasia are exposed to a much high concentration of fetal androgens than are most girls. Once born, CAH can be easily treated, bringing plasma androgens to a normal level, and for the most part these girls live normal lives, as girls. However, the early exposure to androgens results in an increase in male-typical behaviors and preferences, including toy preferences, aggressiveness, frequency of rough-and-tumble play, spatial ability, and other measures (Berenbaum, 1999; Berenbaum et al, 2000).

This should come as no surprise, since it was long ago demonstrated that sex-typical behavioral differences in other mammals, such as mice and rhesus monkies, can be experimentally manipulated by early androgen exposure. By manipulating fetal androgen levels, it is possible to make a XY rodent express female-typical mating behaviors, such as lordosis. Likewise, a XX rodent exposed to androgens will develop male-typical mating behaviors, such as mounting. See, for example, Wilson (1999).


There is no reason to think that gender-typical behavior differences are solely the result of gender-typical socialization, and much evidence to the contrary. Piscez mentioned the famous case of John Theissen (formerly Joan), who was raised as a girl for 14 years and whose case was cited as evidence that gender is solely socially constructed. There are many similar types of cases, where gender assignment is trumped by uncooperative biology. For instance, William Reiner studied the results of gender reassigment in 25 XY individuals who were castrated or were born with the condition of cloacal exstrophy and raised as females. All showed the typical 'male' patterns of rough-and-tumble play, interests and attitudes. Most spontaneously declared they were males, despite being socialized as females.

Then there are the Guevedoces or machihembras of the Dominican Republic. These XY individuals do produce testosterone, but because of a genetic mutation in the gene for 5 alpha reductase type 2, they are unable to efficiently convert the testosterone to the physiologically more active form dihydrotestosterone (DHT). The condition itself is referred to as 5 alpha reductase deficiency. As a result, these children are born with with an ambiguous or female-appearance, which persists until puberty.

The interesting thing is that at puberty, these individuals suddenly are 'masculinized,' developing a much more male-typical phenotype, including enlarged phallus, facial hair, increased muscularity. Since most of these individuals appear more female at birth than male, they are socialized as females. Imperato-McGinley et al (1979) studied 38 individuals with this disorder, 18 of which were raised as girls until puberty. Despite this, "during or after puberty, 17 of 18 changed to a male-gender identity and 16 of 18 to a male-gender role."



Refs

Berenbaum, S. A., 1999. Effects of early androgens on sex-typed activities and interests in adolescents with congenital adrenal hyperplasia. Hormones and Behavior, 35, 102-110.

Berenbaum, S. A., et al, 2000. Behavioral effects of prenatal vs. postnatal androgen excess in children with 21-hydroxylase-deficient congenital adrenal hyperplasia. Journal of Clinical Endocrinology and Metabolism, 85, 727-733

De Vries et al, 2002. A model system for study of sex chromosome effects on sexually dimorphic neural and behavioral traits. Journal of Neuroscience 22, pp. 9005-9014.

Imperato-McGinley et al, 1979. Androgens and the evolution of male-gender identity among male pseudohermaphrodites with 5alpha-reductase deficiency. New England Journal of Medicine 300, pp. 1233-1237.

Kimura, D., 1999a. Sex and cognition. MIT Press.

Kimura, D., 1999b. Sex differences in the brain. Scientific American article. PDF file

Kimura, D., 2002. Sex hormones influence human cognitive pattern. Neuroendocrinology Letters 23, Suppl 4, pp. 67-77.

Wilson, 1999. The role of androgens in male gender role behavior. Endocrine Reviews 20 (5): 726.


Patrick

TomboyMom

Another thing we often forget about sex/gender differences is that the great majority are not opposite, but overlapping bell curves. For example, men are taller than women--the male height bell curve is to the right of, but overlaps with, the female height bell curve. Some women are taller than some men. This is the case for almost all sex and gender differences*, and remembering this helps us to remember to look at individuals instead of genders.

*exceptions: only women can give birth, etc.

Rene

Nostalgic Pushhead

Wow, thanks ps418. Much appreciated.

abe smith

Yo, Petrich: your post here of 21 april:..."Gender identity. We have a strong tendency to perceive ourselves as belonging to one" [sic] "of the sexes."
I've never felt competent to generalize, my Pet'; but I'd like to insert that your generalization about what "we have a strong tendency to" do is not true for at least one alleged member of humankind.
Of course your position may be that anyone who does not share your alleged "strong tendency" is not one of "us".
Your privilege. Or as my poster(about mid1970s) asked as I carried it back & forth in front of Amenia N.Y. Immaculate Conception: "Well, Cardinal Cooke, your God made the "normal"
people. So, who 'created' all the rest of us?"

To be sure, nominalists like me (using the label is itself an oxymoron) do not take kindly to (your) Platonist categories.
Cordially....

abe smith

still acting as a nominalist (who rejects, therefore, labelling systems ==still acting oxymoronically.....) I will ever and always call into question you-all-here's implicit assertion that there "are" always-and-ever TWO and ONLY TWO human "sexes", and that whatever does not fit into your damned manmade category system(s) is ipso facto anomalous.
I expect that if (as so often before) I state mildly
"There are no type-forms in Biology (whether human or other).", your-all's response will be "HUH?" and "Well, of course, Abe's senile...."
The ignorances of religionists-in-power, and of (secular) politicians-in-power, about this as about so many other matters that matter makes me grind my teeth and:banghead:

ps418

There's no need to assume that there can be two and only two human sexes. Yet it is a simple fact that ~99.9 of all humans on earth can be uncontroversially assigned to one sex or the other. Unless you want to start changing the meanings of words, the ~0.01% of ambiguously-sexed humans are indeed anomalous. And I dont agree that there are more than 2 human sexes. There are males, females, and individuals with both male-typical and female-typical characteristics.

Patrick

Corona688

Abe, I'm not certain what you mean. Are you speaking of psychological(but no less real.. not sure if it'e even the right term) differences, as in homosexuality etc? Or are you referring to physical differences?

Nostalgic Pushhead

Hmm saw PS covered my point (more coherently than I), but it won't let me delete this.