Of course you are aware that around the country there are legislative efforts to force transgender people to use the bathroom and locker rooms reserved for the sex we were assigned at birth. In some places, it is phrased rather as requiring those facilities to be segregated by chromosomes.

Awkward, that. As a society, we have never determined assignment of sex at birth by a test of chromosomes. I'm 68 years old and, as far as I know, I have never had my chromosomes tested. Ever.

I find it stranger still that the forces calling for this anti-transgender discrimination have such little regard for science in general. These are people who believe the universe was created between 6000 and 7000 years ago, that a woman was created from the rib of a man, and that Jesus rode to Sunday School on the back of a dinosaur.

I've often seen religious screeds calling science just another belief system...just another form of religion. That comes from the fact that they do not understand what science is...that scientists regularly challenge what they believe to be true and try to prove that an alternative explanation for a phenomenon may be possible. As a mathematician, I've often proved that something is true by proving that no alternative is possible. Religion does not do this. This way of thinking is the province of science.

Anyway, we find ourselves in the middle of a debate about whether chromosomes determined who we are as people...a debate with people who do not even understand exactly what chromosomes are or how they function.

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.

Chromosomes are not visible in the cell’s nucleus—not even under a microscope—when the cell is not dividing. However, the DNA that makes up chromosomes becomes more tightly packed during cell division and is then visible under a microscope. Most of what researchers know about chromosomes was learned by observing chromosomes during cell division.

Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.” The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specific genes.

--NIH

Ah...genes. Very important concept. If one doesn't understand genes, one has no chance of understanding chromosomes.

A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. The Human Genome Project has estimated that humans have between 20,000 and 25,000 genes.

Every person has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but a small number of genes (less than 1 percent of the total) are slightly different between people. Alleles are forms of the same gene with small differences in their sequence of DNA bases. These small differences contribute to each person’s unique physical features.

--NIH

Also important is gene expression, "the phenotypic manifestation of a gene or genes by the processes of genetic transcription and genetic translation."

When genes are expressed, the genetic information (base sequence) on DNA is first copied to a molecule of mRNA (transcription). The mRNA molecules then leave the cell nucleus and enter the cytoplasm, where they participate in protein synthesis by specifying the particular amino acids that make up individual proteins (translation).

--NIH

Errors in transcription and translation can, and do, happen.

Of course, many folks are only interested in the sex chromosomes.

The X chromosome is one of the two sex chromosomes in humans (the other is the Y chromosome). The sex chromosomes form one of the 23 pairs of human chromosomes in each cell. The X chromosome spans about 155 million DNA building blocks (base pairs) and represents approximately 5 percent of the total DNA in cells.

Each person normally has one pair of sex chromosomes in each cell. Females have two X chromosomes, while males have one X and one Y chromosome. Early in embryonic development in females, one of the two X chromosomes is randomly and permanently inactivated in cells other than egg cells. This phenomenon is called X-inactivation or Lyonization. X-inactivation ensures that females, like males, have one functional copy of the X chromosome in each body cell. Because X-inactivation is random, in normal females the X chromosome inherited from the mother is active in some cells, and the X chromosome inherited from the father is active in other cells.

The word "normally" is important here. Besides XX and XY, there are people whose chromosome arrangements are XXY, XXXY, XYY, and XO (missing chromosome).

And there are XY people with androgen insensitivity syndrome (AIS), whose body will develop with all the physical traits of a woman...and XX males (de la Chapelle syndrome).

Chromosomal anomalies occur in an estimated 1 in ever 500 live births. They have varying affects on physical development. Transgender people generally have a different kind of physical anomaly...one that seems to be located in the brain.

While we don't know the precise cause of this condition, it has been hypothesized to be the result of abnormal hormone levels in the uterine environment at crucial moments during pregnancy.

Sex differences may be induced by specific genes, by hormones, by anatomy, or by social learning. Some of the differences are entirely physical (e.g., presence of a uterus) and some differences are just as obviously purely a matter of social learning and custom (e.g., relative hair length). Many differences, though, such as gender identity, appear to be influenced by both biological and social factors ("nature" and "nurture").

Nevertheless, even the sex-dichotomous differences are not absolute in the human population, and there are individuals who are exceptions (e.g., males with a uterus, or females with an XY karyotype), or who exhibit biological and/or behavioral characteristics of both sexes.

--Wikipedia

In most animals, differences of exposure of a fetal or infant brain to sex hormones produce significant differences of brain structure and function which correlate with adult reproductive behavior.

This is the case in humans as well; sex hormone levels in male and female fetuses and infants differ, and both androgen receptors and estrogen receptors have been identified in brains. Several sex-specific genes not dependent on sex steroids are expressed differently in male and female human brains. Structural sex differences begin to be recognizable by 2 years of age, and in adult men and women include size and shape of corpus callosum (larger in women) and fasciculae connecting each hemisphere internally (larger in men), certain hypothalamic nuclei, and the gonadotropin feedback response to estradiol.

The absence of the genes that generate male genitalia do not single handedly lead to a female brain. The male brain requires more hormones, such as testosterone, in order to properly differentiate. Thee hormones are released due to a gene expressed during embryonic development.

--Wikipedia

Though during the first few weeks of fetal development your baby's internal and external genital structures are the same, the organs will eventually change. Your baby's gonads will either become ovaries or testicles. The phallus will become either a clitoris or a penis, and the genital folds will become either labia or scrotum. This all depends whether or not testosterone is present. Testosterone will be present in embryos with a Y chromosome, and male sex organs will begin to form. If testosterone is not present, female organs will develop, making female the "default sex" for human beings.

--Link

The anti-transgender forces believe that biological sex creates gendered behavior.

Testosterone, when released in the womb, causes the development of male sex organs (at 7 weeks) (in the presence of a Y chromosome) and acts upon the hypothalamus which results in the masculinization of the brain.

At the same time testosterone acts on the developing brain. The brain is divided into two hemispheres, left and right. In all humans the left side of the brain is more specialised for language skills and the right for non-verbal and spatial skills.

Shaywitz et al (1995) used MRI scans to examine brain whilst men and women carried out language tasks and found that women used both hemispheres, left only used by men.

--Simply Psychology

Experiments in animals have shown that exposure to testosterone during prenatal development can cause permanent change to the sexually dimorphic nucleus in the hypothalamus.

Hines (1982) studied female babies born to mothers who had been given injections of male hormones during pregnancy to prevent miscarriage. They were found to be more aggressive than normal female children. Hines concluded that the extra testosterone in the womb had affected later behavior.

One should really pay attention to the fact that the uterine environment is just as biological as the sex genes in the chromosomes. It's quite possible that we really should dispense with the term "biological sex."

Of course, the title of this essay asks a different question...one easily answered. Hate is not in the genome. Hate is not heritable. You have to be carefully taught.

Anti-transgender people like to state that we have no right to exist because "God does not make mistakes." On that I can agree. Transgender people are not mistakes. We are real people. To put it in their words: God-created people. God put us here. God must have had a reason. And I cannot believe that our purpose is to see just how badly human beings can be treated. Rather, it is my belief that we are here because God needed to test the Christian actions of his followers.

I'm sure God is sorely disappointed.