October 19, 2002
Brain Gets Sex Orientation Before Genitals

The SRY gene is widely considered as the gene for determining sexual identity. See for instance this page about the role of the SRY gene in determining sexual identity. Also, see this page:

By its structure, the SRY gene is a 1,0 kb one exon gene located just centromeric to the pseudoautosomal region of Yp functioning as the dominant inducer of testis development. This gene comprises a single exon that encodes a 203- amino acid protein. The middle third of the protein represents the HMG (high-mobility group) domain specifically binging to a target nucleotide sequence 5’-AACAAAG-3’ characterising it as a transcription regualtor protein. Although its function is not entirely known, this gene is obviously the first initiator of male sexual differentiation 13, 19, 37, 42.

However, a UCLA team led by Eric Vilain has discovered differences in genetic expression that happen before the SRY gene becomes active during development. It is possible that male-female brain differences start developing before SRY starts changing genitals development:

"But in a study of mice, a team at the University of California, Los Angeles, has now found that males and females show differences in the expression of no fewer than 50 genes well before SRY switches on," according to the magazine.

Eric Vilain, the head of the UCLA team, said three of the genes are dominant in females and four in males, but they still need to determine whether the genes influence brain sexuality in mice and whether the same thing occurs in humans.

You can find the same article here.

Eric Vilain's home page at UCLA provides some more details about his lab's work:

Sex determination orients development toward sexually dimorphic individuals, male or female. In mammals, male sex determination is triggered by a primary signal, encoded by the testis determining factor SRY, localized on the Y chromosome. Subsequently, a complex network of genes, most of them still unknown, is regulated and leads to male sexual differentiation. We have discovered new molecular and cellular mechanisms of sex determination during fetal development. In particular, we have provided strong evidence supporting SRY as the testis determining gene, and identified regulatory mechanisms of transcription of DAX1, another sex determining gene. We have also recently identified human WNT-4, a signalling molecule responsible, when duplicated, for XY sex reversal in mammals. A new concept is now emerging: normal sexual development is highly dependent on strict gene dosage at all major steps of the sex determination pathway.

One possibility this opens up is the ability to separately control genital and brain sexual differentiation. Some day there will be people who have male minds in female bodies and vice versa. They will be more like the opposite sex in their thinking than is the case with homosexuals.

Share |      Randall Parker, 2002 October 19 02:14 PM  Brain Development

Ms. A. T. Sijtsma said at October 21, 2003 1:14 AM:

Dear sir,

Can you send me the data about this study so I can use it for the literature on my paper? I am a master student of psychology in The Netherlands and I am seeking for information about the development of sexual identity.

Thank you!
Annet Sijtsma

F.J.J. Jager said at October 26, 2003 8:13 AM:


Could you also send me the data of this study? At this moment I am gathering information to write a paper about this research.
But until now I only got some global data which will not be sufficient to write my paper.

Thank you,
Fedde Jager

Beto Cubas said at February 11, 2004 7:19 PM:

Mi estimado amigo:
Yo también estoy interesado en los datos de ese estudio para un investigación.
Por favor, ¿me lo puede enviar?

Carrie Small said at June 13, 2004 12:59 PM:

My interest is in adolescent psychopathology. I am also VERY interested in the proactive and preventative angle of addressing psychopathology through available methods (observations, fMRI's, psychophysiological, testing tools, etc.) in finding the pathology BEFORE the behaviors are evident, noticed, or observable. I hope for advancements in these techniques ASAP. In the meantime, I'm interested in postmortem brain studies of embryotic and up looking for differences in vulnerable or susceptible individuals and "normal" (non-pathological) brain anatomy. I don't know where to start to become active in this research. Maybe you will have suggestions.

Thank you!
-Carrie Small

Marco Antonio Correa Varella said at August 24, 2004 11:56 AM:


Could you also send me the data of this important study? I am a graduated student of human biology in Brazil and I am seeking for information about the development of brain's sexual diferenciation into male and female think.

Thank you,

lynn robinson said at May 25, 2005 8:30 PM:

Interesting site. I'm working with "transitional age" youth or "young adults" 18-24.
Interested in recent studies done with post adolescent brain development and its ramifications.

Kevin Butler said at January 11, 2008 2:49 PM:

I find the information that you are proposing very interesting and I was wondering if you could forward me the data so I may also use it in one of my papers. The main focus of which deals with the policy revovling around gay rights and I feel that the information you can provide can help provide a stronger base to my arguement.

Bobin said at April 18, 2008 12:54 PM:

It's all ride

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