On Sex and Gender (part 1)
from Kris Hardies,
04. September 2009, 10:30
I apologize for the long wait, but I was to busy with sex to be doing gender.
There were however some interesting things in the news lately, like South Africa's gold medal winner Caster Semenya, and Swedish parents who keep it a secret if their two-year-old is a boy or a girl.
USING SEX AND GENDER
Before discussing stories like these however, I think that it is necessary to start this blog with some explanation about what I understand under terms like 'sex', 'sex differences', 'gender', and 'gender differences'. Notwithstanding the fact that the word gender has become standard scientific jargon, most of the time, when someone uses the term gender he or she does not actually talk about gender. More often than not gender is just used as a simple synonym, perhaps a euphemism, for sex [1-2]. The terms sex and gender are, thus, most of the time used interchangeable [3] – and even if they are not, it is usually not clear what someone exactly means by them. This is, however, quite problematic since the term gender became widespread after the adoption in the 1970s by feminist scholars as a way of distinguishing 'socially constructed' aspects of male–female differences (gender) from 'biologically determined' aspects (sex).
FROM SPERM AND EGGS TO BODIES AND BRAINS
Human beings are, like all known living organisms, build up out of cells (something of a 100 trillion cells in the case of humans). Human cells have 23 pairs of chromosomes (on which our genes can be found). These chromosomes are transmitted to us by our parents (by the recombination of their sex cells, the gametes, which synthesises into a zygote). Unlike other types of cells these sex cells contain only 23 chromosomes, not 46. Thus, we receive 23 chromosomes from both of our parents. Twenty-two of these chromosomes are matching (homologous) autosomes; they are the same whether they come from our mother of our father. The 23rd chromosome, however, is the so-called sex chromosome and comes in two forms: X and Y. Although these sex chromosomes comprise only 5% of the genome (males and females are thus genetically quite similar) they have some major phenotypical consequences.
In humans (and most other mammals) one group of individuals has (few) large gametes and the other group has (many) small gametes. The group that has large gametes is conveniently called female and always passes true an X chromosome to their offspring, the group that has small gametes is conveniently called male and passes true an X or a Y chromosome to their offspring. The paternally contributed Y chromosome contains the sex-determining region of the Y (Sry) gene, which induces the undifferentiated gonads to form as testes (rather than ovaries), regardless of how many X chromosomes are present. The sex chromosomes differ in three main ways in the zygote: (1) only males have Y genes (very few genes are however Y-linked; the Y chromosome is small, it has only 60 million base pairs out of the total 3 or so billion of the entire human genome, and has approximately only 70 coding genes, 10 times less than the X chromosome), (2) females have two copy numbers of X genes (sex-specific effects of this kind are, however, largely eliminated by X-inactivation), and (3) females receive a parental X imprint that is lacking in males. Consequently, some traits are sex-limited (genes are only expressed in one sex), sex-linked (they appear more often in one sex; e.g. X-linked recessive traits appear far more commonly in males than in females since females possess two X chromosomes and males possess only one), and sex-influenced (these traits are not carried on the sex chromosomes, but their phenotypical expression depends on the interaction with the sex chromosomes [4]).
In normal development [5], genetic sex (XX vs. XY) goes hand in hand with other sex differences. A major consequence of chromosomal sex is the differentiation of the gonads. Females (XX) develop ovaries. Males (XY) on the other hand develop testes that secrete hormones that 'masculinise' the rest of the body. Foetuses of both sexes are exposed to both androgens (e.g. testosterone) and estrogens (e.g. estradiol) from their gonads as well as other sources, such as the adrenal gland, the placenta, and the maternal system. There are, however, dramatic differences in the amounts of various hormones produced by the testes vis-à-vis the ovaries. Adult males produce, for example, approximately 20 times more testosterone per day than adult females (on average, approximately 7 mg versus 0.35 mg). The differential hormone levels between genetic sex differentiated beings can be labelled 'hormonal sex'.
Gonadal hormones are also essential to the sexual differentiation of the brain, mainly as a result of the testicular secretion of testosterone. The classic view of sex differences in the brain begins with differential development of the gonads. Testicularly derived testosterone and its neuronally aromatized end product, estradiol, impact on the development of the brain (organizational effect) and consequently behaviour, through endocrine actions in adulthood (activational effect). However, lately [6] this classic dogma of sexual differentiation has been nuanced since it has been found that the brain is also sexually differentiated as a direct result of chromosomal sex. Thus, genes on the sex chromosomes probably determine the sexually dimorphic phenotype of the brain in two ways: by acting on the gonads to induce sex differences in levels of gondola secretions that have sex-specific effects on the brain, and by acting in the brain itself to differentiate XX and XY brain cells. Since the sexual differentiation of the genitals takes place much earlier on in development (in between 6- and 7- week of pregnancy) than the sexual differentiation of the brain (starting in the second semester of pregnancy and becoming overt upon reaching adulthood), the sexual differentiation of the brain and the body may also be influenced independently of each other. Genetic sex and brain sex are, thus, not necessarily corresponding. Furthermore, the morphology of the brain may be sexually differentiated because of epigenetic mechanisms [7] Mouse data have shown that approximately 650 genes (~ 14% of all genes in this tissue) are expressed differentially in the brains of males and females, around half of which are expressed more highly in females and half of which are expressed more highly in males [8].
MORE SIMILAR THAN DIFFERENT
In discussing sex and sex differences, it should be noted that there is actually too much stress on sex differences (in academia and in popular culture and media). It is true that thousands of studies have documented sex differences in the brain in practically any parameter imaginable [9], but it has also been noted that the male and female brain are in large part the same, that they are more similar than different [10-11]. When an X gene is expressed at a higher level in females, it is not clear whether the sex difference has significant functional consequences [12]. Furthermore, there is the problem that we still know very little about the brain circuitry and how it controls behaviour (despite the progress in molecular and cellular biology) [13] and, thus, in most cases we do not understand how, or even whether, sex differences in brain morphology contributes to sex differences in behaviour [14]. Moreover, it may even be the case that sex differences in the brain precisely exist to prevent, rather than create psychological sex differences [15].
SEX =//= GENDER
To conclude, sex is a biological category. Females have XX chromosomes, males XY. Normally this goes hand in hand with hormonal sex and brain sex differences. The relationship between sex and behaviour is much less clear, to say the least. It is confusing and unnecessary to use the term gender in cases were one is clearly talking about sex (for example when you ask somebody if their baby is going to be a boy or a girl, or when talking about rats). It is just as foolish to use the term sex in cases were one should talk about gender (for example when one is discussing baby names, or colours for baby clothing and shoes; more on this in part 2)
Much of the confound of sex and gender is probably due to the fact that much gendered behaviour is sex-correlated (but not sex-related), i.e. the behaviour is correlated with a person's sex because sex functions as a stimulus; the behaviour is, however, not caused by underlying biological processes [16]. It is a dreary thing that most of these things were already clear thirty years ago, but still it is true that "the major problem seems to be the use of sex differences as an explanatory rather than a descriptive term" [17].
As I will further explain in the second part of this blog-post, sex should not be used interchangeable with gender, and some things are 'sex differences' while other are 'gender differences'. The obvious differences in reproductive physiology (females ovulate on a periodic and regular basis, get pregnant, deliver, and lactate, and males do not) are sex differences. Woman's better sense of smell [18] is also a sex difference. The better scoring of males on mathematical tests and the differences in clothing style between men and women are, however, not.
Much of the confound of sex and gender is probably due to the fact that much gendered behaviour is sex-correlated (but not sex-related), i.e. the behaviour is correlated with a person's sex because sex functions as a stimulus; the behaviour is, however, not caused by underlying biological processes [16]. It is a dreary thing that most of these things were already clear thirty years ago, but still it is true that "the major problem seems to be the use of sex differences as an explanatory rather than a descriptive term" [17].
As I will further explain in the second part of this blog-post, sex should not be used interchangeable with gender, and some things are 'sex differences' while other are 'gender differences'. The obvious differences in reproductive physiology (females ovulate on a periodic and regular basis, get pregnant, deliver, and lactate, and males do not) are sex differences. Woman's better sense of smell [18] is also a sex difference. The better scoring of males on mathematical tests and the differences in clothing style between men and women are, however, not.
Further reading
Jones, S. (2003) Y: The Descent of Men. New York: Houghton Mifflin.
Morris, J. A., C. L. Joran & S. M. Breedlove (2004) Sexual differentiation of the vertebrate nervous system. Nature Neuroscience 7 (10): 1034-1039
Plomin, R. et al. (2001) Behavioral Genetics. New York: Worth.
References
[1] Haig, D. (2000) Of sex and gender. Nature Genetics 25 (4): 373
[2] Haig, D. (2004) Archives of Sexual Behavior 33 (2): 87-96
[3] Some (biological) things are uniquely addressed with the term sex (i.e. gender is never used as a synonym in these instances). This is the case when one refers to things such as sex chromosomes, sexual behaviour, sexual intercourse and related behaviour.
[4] The genetic influences that determine, for example, whether a person will have a high singing voice or a low one are autosomal, but the effects of the alleles are opposite in the two genders. The same allelic combination which produces a high soprano in a woman causes a male to be a low bass, and the combination that producers a high tenor in males produces a low contralto in female.
[5] Fausto-Sterling (1997) claimed that 1.7% of human births are 'intersex' (e.g. XXY), but according to Sax (2002) this is a gross exaggeration which resulted from a too broad definition. According to Sax (2002) intersex occurs in fewer than 2 out of every 10,000 births, making more than 99.98% of humans either male or female. Whatever the precise number may be, the product of normal chromosomal recombination is male or female.
Fausto-Sterling, A. (1997) Beyond Difference: A Biologist's Perspective. Journal of Social Issues 53 (2): 233-258
Sax, L. (2002) How Common is Intersex? A Response to Anne Fausto-Sterling. Journal of Sex Research 39 (3): 174-178
[6] See for example Arnold, A. P. & P. S. Burgoyne (2004) Are XX and XY brain cells intrinsically different? Trends in Endocrinology and Metabolism 15 (1): 6-11
[7] Murray, E. K. et al. (2009) Epigenetic Control of Sexual Differentiation of the Bed Nucleus of the Stria Terminalis. Endocrinology 150 (9): 4241-4247
[8] Yang, X. et al. (2006) Tissue-specific expression and regulation of sexually dimorphic genes in mice. Genome Research 16 (8): 995-1004
[9] Cahill, L. (2006) Why sex matters for neuroscience. Nature Reviews Neuroscience 7 (6): 477-484
[10] Hines, M. (2004) Brain Gender. Oxford: University Press.
[11] Halpern, D. F. (2000) Sex Differences in Cognitive Abilities. London: Erlbaum.
[12] Arnold et al. (2004) Minireview: Sex Chromosomes and Brain Sexual Differentiation. Endocrinology 145 (3): 1057-1062
[13] Peng, W. (2009) Dawn on the mice. Nature Methods 6 (5): 319
[14] de Vries, G. J. & P. Södersten (2009) Sex differences in the brain: The relation between structure and function. Hormones and Behavior 55 (5): 589-596
[15] de Vries, G. J. (2004) Minireview: Sex Differences in Adult and Developing Brains: Compensation, Compensation, Compensation. Endocrinology 145 (3): 1063-1068
[16] Consider the following example. Most genetically male babies are dressed in blue so 'wearing blue clothes' is in our contemporary society clearly correlated with sex (that means that if you know the sex of a baby you will, all other things being equal, be able to make a statistically more accurate prediction as to the colour of the clothes of that baby than an observer ignorant of that baby's sex – or vice versa, knowing the colour of the baby's clothes would give you greater chance in guessing if it is a boy or a girl). It is, however, just as clear that it are not biological process, but social custom that underlie this relationship (boys do not wear blue clothes because they are in possession of an Y chromosome or because they produce more testosterone than girls).
[17] Unger, R. K. (1979) Toward a Redefinition of Sex and Gender. American Psychologist 34 (11): 1085-1094
[18] Dalton, P., N. Doolittle & P. A. S. Breslin (2002) Gender-Specific Induction of Enhanced Sensitivity to Odors. Nature Neuroscience 5 (3): 199-200
Morris, J. A., C. L. Joran & S. M. Breedlove (2004) Sexual differentiation of the vertebrate nervous system. Nature Neuroscience 7 (10): 1034-1039
Plomin, R. et al. (2001) Behavioral Genetics. New York: Worth.
References
[1] Haig, D. (2000) Of sex and gender. Nature Genetics 25 (4): 373
[2] Haig, D. (2004) Archives of Sexual Behavior 33 (2): 87-96
[3] Some (biological) things are uniquely addressed with the term sex (i.e. gender is never used as a synonym in these instances). This is the case when one refers to things such as sex chromosomes, sexual behaviour, sexual intercourse and related behaviour.
[4] The genetic influences that determine, for example, whether a person will have a high singing voice or a low one are autosomal, but the effects of the alleles are opposite in the two genders. The same allelic combination which produces a high soprano in a woman causes a male to be a low bass, and the combination that producers a high tenor in males produces a low contralto in female.
[5] Fausto-Sterling (1997) claimed that 1.7% of human births are 'intersex' (e.g. XXY), but according to Sax (2002) this is a gross exaggeration which resulted from a too broad definition. According to Sax (2002) intersex occurs in fewer than 2 out of every 10,000 births, making more than 99.98% of humans either male or female. Whatever the precise number may be, the product of normal chromosomal recombination is male or female.
Fausto-Sterling, A. (1997) Beyond Difference: A Biologist's Perspective. Journal of Social Issues 53 (2): 233-258
Sax, L. (2002) How Common is Intersex? A Response to Anne Fausto-Sterling. Journal of Sex Research 39 (3): 174-178
[6] See for example Arnold, A. P. & P. S. Burgoyne (2004) Are XX and XY brain cells intrinsically different? Trends in Endocrinology and Metabolism 15 (1): 6-11
[7] Murray, E. K. et al. (2009) Epigenetic Control of Sexual Differentiation of the Bed Nucleus of the Stria Terminalis. Endocrinology 150 (9): 4241-4247
[8] Yang, X. et al. (2006) Tissue-specific expression and regulation of sexually dimorphic genes in mice. Genome Research 16 (8): 995-1004
[9] Cahill, L. (2006) Why sex matters for neuroscience. Nature Reviews Neuroscience 7 (6): 477-484
[10] Hines, M. (2004) Brain Gender. Oxford: University Press.
[11] Halpern, D. F. (2000) Sex Differences in Cognitive Abilities. London: Erlbaum.
[12] Arnold et al. (2004) Minireview: Sex Chromosomes and Brain Sexual Differentiation. Endocrinology 145 (3): 1057-1062
[13] Peng, W. (2009) Dawn on the mice. Nature Methods 6 (5): 319
[14] de Vries, G. J. & P. Södersten (2009) Sex differences in the brain: The relation between structure and function. Hormones and Behavior 55 (5): 589-596
[15] de Vries, G. J. (2004) Minireview: Sex Differences in Adult and Developing Brains: Compensation, Compensation, Compensation. Endocrinology 145 (3): 1063-1068
[16] Consider the following example. Most genetically male babies are dressed in blue so 'wearing blue clothes' is in our contemporary society clearly correlated with sex (that means that if you know the sex of a baby you will, all other things being equal, be able to make a statistically more accurate prediction as to the colour of the clothes of that baby than an observer ignorant of that baby's sex – or vice versa, knowing the colour of the baby's clothes would give you greater chance in guessing if it is a boy or a girl). It is, however, just as clear that it are not biological process, but social custom that underlie this relationship (boys do not wear blue clothes because they are in possession of an Y chromosome or because they produce more testosterone than girls).
[17] Unger, R. K. (1979) Toward a Redefinition of Sex and Gender. American Psychologist 34 (11): 1085-1094
[18] Dalton, P., N. Doolittle & P. A. S. Breslin (2002) Gender-Specific Induction of Enhanced Sensitivity to Odors. Nature Neuroscience 5 (3): 199-200
"I was to busy with sex to be doing gender"
Hahahahaha! :-D
I am not a biologist, but I have read articles in which the SRY gene has been found on the X chromosome; thus, a male body develops despite the fact that the sex chromosomes are XX. Unless I missed it, your article seems to have overlooked this possibility. This gene mutation is rare, but nevertheless does exist. Additionally, as I understand it, the DAX-1 gene can override the SRY gene. Thus, a female body can be produced despite the fact that the SRY gene is present. Thus how the body develops is more complicated than the experts have previously believed.
Dear Lisa Anderson Mares,
First of all, my apologies for my (ridiculous) late response. Second, you are absolutely right. Although it seems that the Sry gene is necessary for masculine development (i.e. development of testes), it does not have to be on the Y chromosome (it can be translocated onto an X chromosome; so that a 46,XX person may develop along a typical masculine pathway). And indeed, the idea that female is the "default" sex in development seems to be incorrect (the feminine pathway is actively triggered by some genes; it is not the result of a default passive sex determining pathway).
Unfortunately, very much is in fact still unknown about sex determination. A very interesting website is: http://www.learner.org/...units/gender/index.html, with interesting interviews about 'the biology of sex and gender' with Holly A. Ingraham, David Page, and Eric Vilain.
In regard to: "[5] Fausto-Sterling (1997) claimed that 1.7% of human births are 'intersex' (e.g. XXY), but according to Sax (2002) this is a gross exaggeration which resulted from a too broad definition. According to Sax (2002) intersex occurs in fewer than 2 out of every 10,000 births, making more than 99.98% of humans either male or female. Whatever the precise number may be, the product of normal chromosomal recombination is male or female. "
I was wondering about the population of peoples who have CAH (the Mayo Clinic online has a reputable definition for this) or similar "syndromes) such as xxy or xo or xyy etc who function more or less normally (who doesn't get nauseous every once in a while, just one of the many symptoms that could be due to poor diet, rather than genetics) - are all these people defined as intersex? if not, what is the boundary of someone who is intersex versus "not" intersex? If it is not solely chromosomal (CAH people have standard xx or xy) and not purely hormone levels (people with xx and xxy may have similar levels of Estrogen and Testosterone, more so than two people with xx) and not based on the ability to function in society (xo, xxy, etc normally don't know they are intersex until they start menstruating out of their anus - such as a friend of mine), then is it a combination of those features? if so, who gets to decide this and how is that process anything other than objective?
Given the above, I am curious as to reliable stats for all those with "syndromes" (xxy etc) and CAH, hypogonadism, etc - if we were to first, have reliable stats for those populations, and also to figure out how many people are born like that out of every 1,000 or so births, might we not see a much larger population that may render "explicitly" "male or female" populations in the minority (if not a more general split)?
The reason I ask so many questions is that I am writing a thesis on a similar topic, and I was curious your input on this theory because this is on of the best and scientifically respectable works I have come across in a long time (and I've read a lot of stuff! haha)
In any case, I appreciate the time you took to read this and respond in any way you can.
Dear Chris Gauthier,
Once again I have to apologies for my late response (and thank you for your compliments).
Let it first be very clear that it is extremely difficult to estimate the frequency of intersexuality. Irrespective of your precise definition, intersexuality is always going to be a "rare" event and you would thus always need very large samples to have some reliable estimates. Since frequencies appear to vary across populations the situation is, however, even more complicated than that because it is unclear what would constitutes as a random sample. To the best of my knowledge, the only systematic review on this subject is an article by Melanie Blackless, Anthony Charuvastra, Amanda Derryck, Anne Fausto-Sterling, Karl Lauzanne, and Ellen Lee from 2000 ("How sexually dimorphic are we? Review and synthesis". American Journal of Human Biology, 12 (2):151-166.)
This article includes estimates on intersexuality "at all levels" (i.e., any intermediate sexual phenotype that is in-between what's commonly accepted as male or female at either the chromosomal, anatomical, gonadal, genital, or hormonal level). Specifically, the following conditions were labeled as intersex: (1) Classical CAH (0.0779%), (2) Late-onset CAH (frequency 1.5%), (3) Klinefelter (XXY) (frequency 0.0922%), (4) Turner syndrome (XO) (frequency 0.0369%), (5) Other non-XX, non-XY (thus excluding Klinefelter and Turner, frequency 0.0639%), (6), Vaginal agenesis (frequency 0.0169%) (7) Complete androgen insensitivity (frequency 0.0076%), (8) Partial androgen insensitivity (frequency 0.00076%), (9) Idiopathic (frequency 0.0009%), and (10) True hermaphrodites (frequency 0.0012%).
If you do or do not consider all this conditions to be forms of intersexuality (according to Sax [2002] late-onset CAH, vaginal agenesis, and non-XX and non-XY chromosomal variations (including Turner syndrome and Klinefelter syndrome) are not to be considered as intersex) depends on your own point of view (and probably the research question you are studying on). I do not think that there are "objective" criteria to determine which of these syndroms are "truly" conditions of intersexuality and which are not.
Thanks for this. I have a post on a similar topic, which I actually lifted from the module we are using in the classroom.
I'm glad someone else is willing to clarify things! As a writer the frequent misuse of the terms irritates me. I did a short blog post on the subject at http://karldrinkwater.blogspot.com/...-gender.html