Sex: female, male or in-between?


A happy couple marrying in St. Petersburg (image credit: Роман Мельник)

Are there really only two sexes? Is it “unnatural” to be somewhere between female and male and is it a choice?

In many human societies the idea of two sexes is very strong, so strong that people are willing to commit atrocious acts of violence to those challenging this idea. It is often argued that it is “unnatural” to not be able to define yourself as either female or male or feel like you were born with the “wrong” sex.

But how “unnatural” is it really? How about the biology of the sexes? Are there only two sexes or are there more?

The definition of sex

The definition of sex given from the World Health Organization (WHO) is:

‘sex’ refers to the biological and physiological characteristics that define men and women


‘male’ and ‘female’ are sex categories.

If you then are tempted to argue that the sexes ‘male’ and ‘female’ are defined according to their ability to produce offspring with each other, you will run into some trouble. Nature could not care less:

Clone yourself but if it gets cold outside: make a male and have sex with him

Pant lice (aphids) have babies with themselves and produce wingless aphid clones (parthenogenesis) all through the summer, simply because this is the fastest way to produce offspring. Thus, there are only females during summer (with a few poor exceptions).

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Plant lice: sex or no sex? (image credit: Luc Viatour)

As the autumn arrives and with it cold temperatures and short days, the lice that are born are both male and female. Mating is then carried out between female and male lice, the result being winged offspring that can fly away somewhere nice to hide and survive the winter. It is all very practical!

Sexual reproduction is there to ensure high genetic diversity. If we were all clones with identical DNA, a single unfortunate illness could wipe out an entire population. If we are all different, some will be less and other more resistant against different diseases. Thus, diversity stabilizes a population: genetic diversity is biologically important.

The aphid case is an example of a trade-off between very fast reproduction and the risk of illness and disease.

Why Nemo’s dad would turn into Nemo’s mum

Clown fish are always born male and later develop into females. They live in groups where the strongest most aggressive fish becomes the female. If she dies, the aggressive runner up will turn into the sugar mommy. Therefore in “Finding Nemo”, Nemo’s dad would eventually turn into a female.

Nemo's dad - a really interesting story.(image credit: Nhobgood Nick Hobgood)

Nemo’s dad – a really interesting story.(image credit: Nhobgood Nick Hobgood)

There are thousands of examples from the animal kingdom where the idea of the traditional sexes are challenged and plant sex is even more peculiar.

That evolves what makes most sense according to the selective pressure exerted on that particular organism. Morals have no place here, just practicality and chance: maximize reproduction. Sometimes unexpected genetic things happen: there are always some individuals in a population who function slightly differently. This is normal and it will always be like that. Deal with it.

The human sexes

If we want to define sexes in humans as only “male” and “female”, we need to come up with a good definition of said female and male. Most people would simply explain that “a male is the one with the penis” and “the female the one with the vagina” and that the two sexes can reproduce. In genetic lingo, we would say that the phenotype is either male or female: The outer characteristics suggest that the person is either female or male. Still, it is kind of subjective as you will soon understand.

Due to genetic reasons, there are a number of variations on the sex-theme. There are for example genetic males with vaginas. Are these people a third sex? Does it matter?

Some genetic variations of the human sexes

The classical genetic definition of a female is that the person has two X-chromosomes and the male has one Y and one X chromosome. However, there are all sorts of variations on the theme depending on what happens during meiosis when the sex-cells: the sperm and the egg are formed.

type genotype phenotype comment
Polysomy XXX,XXXX female Varying effects on the body. Might go undetected.
Kleinfelter syndrome XXY male There are variations of Kleinfelter’s where the extra X is inactivated in parts of the body – creating a mosaic genetic pattern.
Turner syndrome XO female There are often some developmental problems
Polysomy XXY male You have an extra chromosome
Standard male XY male classic male
Mutation on Y XY female less common female
Standard female XX female classic female
Mutation on X XX male less common male

Therefore it is ludicrous to have moral objections on the definition of sex. Such objections are about as logic as me having moral objection of it being too bloody cold in Sweden. I feel terribly offended that we get less sunlight at higher latitudes than at the equator.

Also, if someone feels like a particular gender, would not the most practical solution for all be not to worry about it and let everyone decide for themselves how they chose to live?

Go moralize around climate change or Shells arctic drilling of oil – or maybe the Congo-conflict?

Contact me, if you would like to get more suggestions of alternative things you could spend your moral energy on.

Laverne Cox: an awesome actress. (image credit: Dominick D)

Laverne Cox: an awesome actress and LBGT advocate.
(image credit: Dominick D)

What do you think of the matter? Do you worry about the sex of other people or yourself and what do you think about gender definitions in contrast to definitions regarding sex?

Science Safely!

...thinks we should care more about peoples actions and less about how their genitals look.

…thinks we should care more about peoples actions and less about how their genitals look.

Ogawa, Kota; Miura, Toru  (2014). Aphid polyphenisms: trans-generational developmental regulation through viviparity. FRONTIERS IN PHYSIOLOGY  Volume: 5     Article Number: UNSP 1   Published: JAN 24 2014

Hughes, Jennifer F.; Rozen, Steve (2012). Genomics and Genetics of Human and Primate Y Chromosomes. Edited by: Chakravarti, A; Green, E. ANNUAL REVIEW OF GENOMICS AND HUMAN GENETICS, VOL 13  Book Series: Annual Review of Genomics and Human Genetics   Volume: 13   Pages: 83-108   Published: 2012


Posted in Animals, Biology, Debate, Genetics, Medicine and tagged , , , .


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