Some interesting responses so far. I'd love to see some scientific links to back up if possible.
Anonymous - yep he's a very eminent medically trained doctor and one of the world's leading experts in his field of psychiatry.
Yes, the brain can alter DNA. This is the remarkable finding of Epigenetics. We already know that RNA, which closely relates to DNA, can be deployed by some animals to edit genetic instructions
https://www.newscientist.com/article/2127103-squid-and-octopus-can-edit-and-direct-their-own-brain-genes/Epigenetics is a truly remarkable area
https://en.wikipedia.org/wiki/EpigeneticsThere is increasing evidence that are we much less set in stone than was previously thought:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1392256/"Another significant epigenetic process is chromatin modification. Chromatin is the complex of proteins (histones) and DNA that is tightly bundled to fit into the nucleus. The complex can be modified by substances such as acetyl groups (the process called acetylation), enzymes, and some forms of RNA such as microRNAs and small interfering RNAs. This modification alters chromatin structure to influence gene expression. In general, tightly folded chromatin tends to be shut down, or not expressed, while more open chromatin is functional, or expressed.
One effect of such processes is imprinting. In genetics, imprinting describes the condition where one of the two alleles of a typical gene pair is silenced by an epigenetic process such as methylation or acetylation. This becomes a problem if the expressed allele is damaged or contains a variant that increases the organism's vulnerability to microbes, toxic agents, or other harmful substances. Imprinting was first identified in 1910 in corn, and first confirmed in mammals in 1991."
And note this:
"Manel Esteller, director of the Cancer Epigenetics Laboratory at the Spanish National Cancer Center in Madrid, and his colleagues evaluated 40 pairs of identical twins, ranging in age from 3 to 74, and found a striking trend, described in the 26 July 2005 issue of Proceedings of the National Academy of Sciences. Younger twin pairs and those who shared similar lifestyles and spent more years together had very similar DNA methylation and histone acetylation patterns. But older twins, especially those who had different lifestyles and had spent fewer years of their lives together, had much different patterns in many different tissues, such as lymphocytes, epithelial mouth cells, intra-abdominal fat, and selected muscles.
As one example, the researchers found four times as many differentially expressed genes between a pair of 50-year-old twins compared to 3-year-old twins, and the 50-year-old twin with more DNA hypomethylation and histone hyperacetylation (the epigenetic changes usually associated with transcriptional activity) had the higher number of overexpressed genes. The degree of epigenetic change therefore was directly linked with the degree of change in genetic function."
Researchers have identified about 80 human genes that can be imprinted.
That leaves a lot that cannot be, but there is evidence that amongst which might be altered are hormones and chromosomes: which we already know to be far more complex simply than XX and XY, for instance around SRY-genes.
