Sex is not genetically determined via X & Y chromosomes

Sex redefined

Sex can be much more complicated than it at first seems. According to the simple scenario, the presence or absence of a Y chromosome is what counts: with it, you are male, and without it, you are female. But doctors have long known that some people straddle the boundary – their sex chromosomes say one thing, but their gonads (ovaries or testes) or sexual anatomy say another. Parents of children with these kinds of conditions – known as intersex conditions, or differences or disorders of sex development (DSDs) – often face difficult decisions about whether to bring up their child as a boy or a girl. Some researchers now say that as many as 1 person in 100 has some form of DSD.

Claire Ainsworth, Sex redefined, nature, 18 February 2015.

Today the SRY gene is understood as one among the many essential mammalian sex-determining factors that are involved in the genetic pathways of both testicular and ovarian determination. Mammals require cascades of gene product in proper dosages and at precise times to produce functioning male and female gonads, and researchers recognize a variety of healthy sexual phenotypes and sex determination pathways in humans.

Sarah Richardson, Sex Itself, University of Chicago Press.

In fact, the sex you develop as isn’t directly genetically determined at all, but instead depends on the action of gonadal hormones during the critical period when your prenatal development is taking place. All the X and Y chromosomes do is determine whether you develop testicles or ovaries, it’s the hormones produced by those organs that actually determine whether you develop as male or female.

Unfortunately, most doctors and pharmaceutical industry decision makers also subscribe to the myth that sex is genetically determined, which is why they’ve not appreciated the dangers of giving hormones to pregnant women, and why we’ve ended up in a situation we’re in today (where large numbers of people have been born who’ve undergone partial or complete opposite-sexed brain development, as a result of being exposed to hormone-disrupting drugs such as DES – find out more about DES studies on gender identity).

Hugh Easton, DES Son.

Sex isn’t chromosomes: the story of a century of misconceptions about X & Y, newstatesman, 23 FEBRUARY 2015. Chromosomes by C. Smith.

The influence of the XX/XY model of chromosomal sex has been profound over the last century, but it’s founded on faulty premises and responsible for encouraging reductive, essentialist thinking. While the scientific world has moved on, its popular appeal remains.

2 thoughts on “Sex is not genetically determined via X & Y chromosomes”

  1. Days after I started life in my mothers womb and after the selection process selected XY on my gender code my full gender really wasn’t finalized. You see it was now the job of germ cells to convey that gender information to the now developing but incredibly small fetus. To pass this information along it needs to physically travel though the midline of that fetus to were the rudimentary gonads reside. I like to think of these gonads as stem cells but in reality they are fetal ovaries. When enough of these germ cells reach each of these fetal ovaries this is when the actual gender changes start. If your male these change to testis and female will cause them to continuing to mature as ovaries.
    There are many steps in the fetal development process that has to happen for the process to provide for complete gender differencation. Most of the time the process progress from one phase to another without any issues. Even when there are issues the body has great latitude in adapting.
    Now let’s backup to myself in the earliest days of fetal development when those germs cells were making their way though my fetal structure. That is when something happened, those germ cells stopped moving and became lodged in place. In my case they were found along the midline of my upper to lower abdomen. Surgery as an adult found the right testis was infact a fetal ovary with the left testis having developed but never to the size as seen in adult males.
    Yes technically I am a male but phycologicaly I lay clearly in the ambiguous area of intersex. Had my one testis not develop at all I would be classified as a women with male DNA or a host of combinations.
    Because of poor medical care that compromised ovary/testis became malignant with, you guessed it ovarian cancer.
    If there is just one thing I wish people to remember is that gender determination is a series of events that need to take place over the first six weeks of development. This is when the baby really takes on the adult sex and leaving the fetal girl sex behind.

    Growing evidence suggests fetal exposesure to hormones not normally found in such concentration in nature are the issue in some cases. In others it could be chance or other toxins to blame.
    I don’t know for sure if I was exposed to DES or just what cause me to develop this way. I do know that three of my spouses eight siblings show clear sights of DES exposeure. My spouse and one other sibling display some factors that could be DES related. We will never know for sure.
    For those who are surprised I did marry. But I deal day to day with the effects.

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