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The biology of gender is the physical basis for behavioural differences between men and women. It is more specific than sexual dimorphism, which covers physical and behavioural differences between males and females of any sexually reproducing species. Biological research of gender has explored such areas as: intersex physicalities, gender identity, gender roles and sexual preference. Late twentieth century study focussed on hormonal aspects of sexual dimorphism in Homo sapiens. With the successful mapping of the human genome, early twenty-first century research started making progress in understanding gene regulation in the human brain.
In 2006, Alexandra M. Lopes and others published that:
|“||A sexual dimorphism in levels of expression in brain tissue was observed by quantitative real-time PCR, with females presenting an up to 2-fold excess in the abundance of PCDH11X transcripts. We relate these findings to sexually dimorphic traits in the human brain. Interestingly, PCDH11X/Y gene pair is unique to Homo sapiens, since the X-linked gene was transposed to the Y chromosome after the human–chimpanzee lineages split.||”|
The late twentieth century saw an explosion in technology capable of aiding sex research. John Money and Milton Diamond made great progress towards understanding the formation of gender identity in humans. Extensive advances were also made in understanding sexual dimorphism in other animals. For example, there were studies on the effects of sex hormones on rats. The early twenty first century started producing even more amazing results concerning genetically programmed sexual dimorphism in rat brains, prior even to the influence of hormones on development.
|“||Genes on the sex chromosomes can directly influence sexual dimorphism in cognition and behaviour, independent of the action of sex steroids.||”|
Skuse, David H (2006). Sexual dimorphism in cognition and behaviour: the role of X-linked genes. European Journal of Endocrinology 155: 99-106.
Some specific relevant results are as follows. The brains of many animals, including humans, are significantly different for males and females of the species (Goy and McEwen, 1980). Both genes and hormones affect the formation of many animal brains before "birth" (or hatching), and also behaviour of adult individuals. Hormones significantly affect human brain formation, and also brain development at puberty. Both kinds of brain difference affect male and female behaviour.
Brain differences also have a statistically measurable effect on an array of abilities. In particular, on average, men are more capable in space and logic while female brains tend to be good at sensory processing. This means the average scores of young men and women in mathematics, for example, will be close, but there will be more men than women in the very low scores and in the very high scores (like red and green, or red and blue). There is evidence to suggest that forms of autism may be essentially extreme expressions of certain typically male characteristics.  Hormones have also been linked with male aggression.
There is a lot of variation in men and women that is not yet understood. It cannot be proven that male-ness or female-ness is 100% biological (in fact it almost certainly isn't), but what has been shown is that male-ness and female-ness are certainly not 100% determined by upbringing and culture (social determinism). These issues remain an area of ongoing research, with profound relevance for people of many different types.
For an illustrated description of clear differences between male and female brain response to pain see Laura Stanton and Brenna Maloney, 'The Perception of Pain', Washington Post, 19 December 2006.
Research and ethics
One important thing to note about the biological research is that most of it was generally motivated by seeking the causes of diseases in human beings, and ways of treating or preventing those diseases. For example, there is study into genetic predisposition to, or causes of, Alzheimer's disease and mental illnesses. Also:
|“||Scientists have cracked the code of an essential signal in the sequence of steps that controls the molecular choreography of gene regulation. The discovery is expected to aid development of therapies and prevention strategies for certain genetically triggered diseases such as breast cancers, pediatric cancers, and leukemia.||”|
Kennedy, Barbara K (2001). Key Step in Gene Activation Discovered. Science Journal 18.
Research results are relevant to gender issues, but that is not their direct concern. Sexual dimorphism in the brain is important to study, because we may need to apply different kinds of treatment to women and to men. Injections for tetanus work the same for men and women, but involve biological intervention to promote health.
Perhaps one day science may be able to tell us how we could stop patriarchy by biological intervention; but science can't tell us if patriarchy is a kind of disease. This takes us back to the importance of the moral questions. Pierre Bourdieu, in 1998 wrote:
|“||Male domination is so rooted in our collective unconscious that we no longer even see it. It is so in tune with our expectations that it becomes hard to challenge it. Now, more than ever, it is crucial that we work to dissolve the apparently obvious and explore the symbolic structures of the androcentric unconscious that still exists in men and women alike. What are the mechanisms and institutions which make possible the continued reproduction of this age-old domination by men? And is it possible to neutralise them in order to liberate the forces for change which they are instrumental in blocking?||”|
So, if an injection could remove male dominance behaviour, should it be made law for such an injection to be given? Should parents be given the choice, or only mothers? These are ethical questions normally thought to require informed debate. The text of this article has provided information from a number of sources, and recorded different positions offered in the debate so far. There are still many unknowns, but new research is being both conducted and published every year. One new journal (available since 2002) is devoted exclusively to Genes, Brains and Behavior. More literature is provided below.
- Platypus (complex sex chromosomes)
- Alexandra M. Lopes and others,'Inactivation status of PCDH11X: sexual dimorphisms in gene expression levels in brain', Human Genetics 119 (2006): 1–9.
- Charles Darwin, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, (London: John Murray, 1859).
- Charles Darwin, The Descent of Man, and Selection in Relation to Sex, 2 volumes, (London: John Murray, 1871).
- Helena Cronin, The Ant and the Peacock: Altruism and Sexual Selection from Darwin to Today, (Cambridge: Cambridge University Press, 1991).
- Robert W Goy and Bruce S McEwen. Sexual Differentiation of the Brain: Based on a Work Session of the Neurosciences Research Program. MIT Press Classics. Boston: MIT Press, 1980.
- Camilla Persson Benbow and Julian C Stanley, 'Sex Differences in Mathematical Reasoning Ability: More Facts', Science 222 (1983): 1029-1031.
- Simon Baron-Cohen, 'The Extreme-Male-Brain Theory of Autism', in H Tager-Flusberg (ed.), Neurodevelopmental Disorders, (Boston: The MIT Press, 1999).
- Simon Baron-Cohen. Mindblindness: An Essay on Autism and Theory of Mind. (Boston: The MIT Press, 1997).
- Elizabeth J. Susman, Gale Inoff-Germain, Editha D. Nottelmann, and others, 'Hormones, Emotional Dispositions, and Aggressive Attributes in Young Adolescents', Child Development 58 (1987): 1114-1134.
- Pierre Bourdieu, 'On Male Domination', Le Monde Diplomatique English edition (October 1998).
- Jonathan Marks. 'Essay 8: Primate Behavior'. In The Un-Textbook of Biological Anthropology. Unpublished, 2007.
- Francesca Lunzer Kritz. 'Not Feeling Each Other's Pain: Men and Women Hurt Differently – and Some of The Difference May Really Be in Their Heads'. The Washington Post. 19 December 2006. Page HE01.
- International Behavioural and Neural Genetics Society
- Council for Biblical Manhood and Womanhood
- Baron-Cohen, Simon. The Essential Difference: The Truth about the Male and Female Brain. New York: Perseus Books Group, 2003.
- Brizendine, Louann. The Female Brain. New York: Morgan Road Books, 2006.
- Brown, Donald E. Human Universals. New York: McGraw Hill, 1991.
- Moir, Anne and David Jessel. Brain Sex: The Real Difference Between Men and Women.
- Pinker, Steven. The Blank Slate: A Modern Denial of Human Nature. London: Penguin Books, 2002.
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