There is no such thing as “gay gene” but the abyssal poverty of genetomania is alive and well

For 40 years and the genetic revolution, it seems that everything is due to genetic mutations! There were the genes of intelligence, of crime and of course homosexuality. In a first draft, a few years ago, there were changes in the size of certain brain structures before we realized that the sample sizes made it impossible to make any conclusions and that the data were not very convincing. The journal Science resurrects this approach with data on more than 500,000 individuals of both sexes, comparing the genomes of homosexual and heterosexual people. 5 sites seem to be associated with homosexuality, 2 of which seem to be related to regulation of sex hormones and olfaction. We arrive by aggregating disparate results at 8 to 25% of variations in homosexuals (men and women) compared to heterosexuals. There is neither data linking these genetic mutations to established functions, nor identified signal cascades – the link with olfaction is at most a correlation. Thes same genetic mutations also concern smoking, using cannabis, taking risks in life! The authors recognize that genetics is a weak factor and that the environment is crucial. All this will not prevent shortcuts in the media.

One remains amazed at the resistance of genetomania for 4 decades with results as low not to say lamentable. In the field of neurological and psychiatric diseases, we have been listening for ages to the genetic cause of autism, schizophrenia, Parkinson’s disease, Alzheimer’s, etc. With several hundred mutations supposed to be involved, we always come to a peremptory decision that genetics intervenes for 15 to 25% in autism, with calculations worthy of a fortune teller, and that tomorrow these numbers will reach 100%, you just need patience and more resources for this type of research.

In Parkinson’s disease, it is perhaps 1-2%, as for most other brain diseases. Plus, we have been promised for ages to cure all these diseases through genetics, except that there is no treatment coming decades after the identification of the mutations, including for diseases in which genetic data are convincing. This is the case, for example, in Huntington’s chorea or Rett’s syndrome.

The only treatments under development for autism have no connection with genetics but result from work on the mechanisms of the pathology and cerebral maturation. One remains confused before so much persistence in the error. The environment – especially during pregnancy and the first years of life – is crucial for understanding and treating these disorders. Genes and environment operate in series and it is impossible to dissociate them. We will not save the groundwork on the pathogenesis of these diseases and how genes and environment interact to produce the changes in neural networks that cause neurological and psychiatric diseases.

Source: Ganna et al. « Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior. » Science 365.6456 (2019): eaat7693.

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