It seems so simple. A man is a man, and a woman is a woman. We know the sex of the baby immediately at birth and we write that down on the birth certificate. Done. No questions, no issues, that is the “fact”.
However….
Like most things in the real world, it really isn’t quite so simple.
Sometimes we fall into a homocentric trap, believing that Humans are the ultimate evolutionary animal and are perfect. Yet, we are just one island in the evolutionary river, and we are also biologic organisms subject to the same types of mutations and genetic errors that happen in all organisms on this planet.
So, let’s take a look at what makes a person male or female.
- (Spoiler Alert: there is a spectrum of answers.)
In general, a male has a penis, testes and prostate; a woman has a vagina, ovary and uterus.
Some people, for either religious, political, or personal reasons maintain that any person with a penis is a man; any person with a vagina is a woman. Or some say that anyone who makes ova is a woman and anyone who makes sperm is a man.
Scientifically, this is incorrect, both in animals in general, and humans in particular. There are many variations that don’t fit that rule.
THE BASICS
So, let’s start at the basics: As we were taught in high school, when a baby is created, the mother contributes one of her X chromosomes and the father contributes either his X chromosome or his Y chromosome.
If the baby has 2 X chromosomes (XX), the baby will develop into a female. If the baby has both 1 X and 1 Y chromosome (XY), the baby will develop into a male.
Why?
The “default” sex is female, defined by the X chromosomes. However, when there is a Y chromosome present, then genes in that chromosome can supersede the default condition and the baby will develop male attributes. Interestingly, there are only a couple of genes on the Y chromosome that cause this change.
The point here is to think about what happens when there are mutations in those “male” genes on the “male” Y Chromosome. Remember that mutations in genes during embryonic development are not uncommon and can result in genetic abnormalities such as Down’s Syndrome, Tay-Sachs, Sickle-Cell Anemia, Huntingdon’s Disease, Cystic Fibrosis, and Cleft Palate.
Since those same “rules” apply to all genes, they also apply to those few genes on the Y chromosome that influence the development of male characteristics.
The types of changes that can occur from these mutations in Y chromosome genes are pretty easy to understand and predict. For example, one of the genes on the Y chromosome that defines your sex is the gene that codes for the production of male hormones. Circulation of these androgens (testosterone is one of them) is important for embryonic development of male characteristics. Not only is it necessary to produce these male hormones, but it is also equally necessary to produce the counterparts of that sub-system, namely the receptors on cell surfaces that can actually “see” the male hormone. It is only when both of those elements are present, the male hormones and the receptors on cells that can be triggered by those hormones, that male characteristics can develop.
When the genes coding for the hormones are mutated so that they create less effective hormones, or the receptor is mutated and loses some, or all of its ability to be triggered by those hormones, that XY baby may not fully develop all male characteristics.
When babies with both an X and Y chromosome have alterations to a gene on the Y chromosome, what happens then?
The baby may develop external male genitalia, but they may ALSO develop internal female genitalia which often are not discovered until later in life, after surgery or an imaging test. This type of condition is referred to as “intersex”, and may affect the genitals, the chromosomes, hormone production and physical parts of the reproductive system.
The result is that, because of defective genes in the Y chromosome, there are “women” walking around, leading normal lives, who actually have XY chromosomes.
In some XX babies, mutations on X chromosome genes can “create” androgens. A condition called CAH in female embryos results in the creation of adrenal glands that produce male hormones. These cases can result in ambiguous genitalia; some labia can actually fuse to create a scrotum below the clitoris, making it difficult to determine externally whether the baby is male or female.
In some people, there are multiple copies of some of the genes on the X chromosome that code for the development of female genitalia. So, even in babies with X and Y chromosomes, there are people who develop external male genitals, but also have a rudimentary uterus and Fallopian tubes.
Another complication in development is that some people develop with more than just 1 X and 1 Y chromosome. Some people are XXY, XYY, XXX, etc. To make this even more thorny, there are people who have some cells with XX chromosomes, while other cells in the same body, have XY chromosomes.
These individuals may develop “ovotestes”, organs that can make BOTH eggs and sperm.
These deviations from “ideal” male or “female” occur surprisingly often. Somewhere between 1.5% and 2% of all births have some variation. And these intersex variations, resulting from changes in genes, can actually be inherited.
There are well documented differences in the brain of a male and a female, larger areas in some or smaller in the other.
The development of the brain is influenced by the circulating hormones during embryonic development. We are only at the very beginning of understanding how the brain works, so it is extremely difficult, in this moment in time, to identify which parts of the brain affect how we view ourselves sexually. What we do understand is that the “limbic” system in the brain contains several clearly defined structures that are involved in sexuality. When one of these structures is damaged, either by injury or during development, sexual urges can be either enhanced or reduced.
We simply do not know how the brain tells us who we should be attracted to and how we should respond, but we do know that it DOES. We can certainly understand that changes in these brain functions, triggered by hormones during embryonic development, environmental factors during the first 10 years of life (while the brain is still developing), or other elements that we don’t understand yet, can affect the way your brain reacts to sexual stimuli.
So, what is a Man?