October 24, 2009
Brain Sex Differences In Gene Expression Start Early

Cognitive differences in the brain start early. Y chromosome genes turn on and alter brain development in fetuses before birth.

Prenatal sex-based biological differences extend to genetic expression in cerebral cortices. The differences in question are probably associated with later divergences in how our brains develop. This is shown by a new study by Uppsala University researchers Elena Jazin and Björn Reinius, which has been published in the latest issue of the journal Molecular Psychiatry.

Do any ideologues still maintain that fundamental sexual differences in cognition are a product of social environment? The science doesn't seem like it leaves any room for a serious argument along those lines.

Professor Elena Jazin and doctoral student Björn Reinius at the Department of Physiology and Developmental Biology previously demonstrated that genetic expression in the cerebral cortices of human beings and other primates exhibits certain sex-based differences. It is presumed that these differences are very old and have survived the evolutionary process. The purpose of the new study was to determine whether they appear during the process of brain development or first upon the conclusion of that process. Identifying the initial genetic mechanisms that prompt the brain to develop in a female or male direction is a long-range research objective.

The Uppsala University researchers analysed data, on the basis of sex, from another extensive study of the prenatal human brain.

"The results show that many of the genes situated on the Y chromosome are expressed in various parts of the brain prior to birth and probably provide a developmental basis for the sex-based differences exhibited by adult brains," according to Elena Jazin.

More than a third of Y-chromosomal genes appear to be involved in sex-based human brain differentiation. Some of the genetic activity in question is evident in the adult brain, while other of it only appears at earlier stages of brain development. It is yet unknown whether the differences in genetic expression among female and male brains have any functional significance.

It would be interesting to know how how prenatal brain gene expression differs in people who grow up to be homosexual. But it seems hard to conduct such a study. Sexual orientation wouldn't become clear for many years.

Share |      Randall Parker, 2009 October 24 11:52 PM  Brain Sex Differences

matlock said at October 25, 2009 1:42 PM:

'Do ideologues still maintain that fundamental sexual differences in cognition are a product of social environment'? I think the answer to that is yes, yes and more yes.

Thought process:

1. If there were differences that would be sexist and therefore there are no differences. All social.

2. If differences are found then it's genetic determinist and the study is flawed and sexist. Still not proven. All social.

3. Alright, there are differences but they are small and can be ignored. Complex interaction, blah, blah. Ignore genes. Focus on social.

4. OK, there are some differences that might be significant - but humans operate within a wide range of our genes. Mustn't talk about it as then we will stereotype and increase differences. Focus on social and discrimination and reducing outcome differences.

5. OK - differences aren't going away. Additional political measures to ensure sameness of outcomes required.

random said at October 26, 2009 7:43 AM:

There has been some (disputed) research indicating there may be environmental influences in homosexuality due to birth order: http://en.wikipedia.org/wiki/Fraternal_birth_order_and_sexual_orientation

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