In this video we are going to be covering the completely
uncontroversial topic of biology’s role in sex and gender development.
So, is how masculine or feminine you are due to the levels of hormones like testosterone and
Oestrogen in your blood stream? And what happens if someone isn't born with the typical XX or XY
combinations, can you have an extra chromosome so XXY? Or one less, so just X? Let’s take a look
THE ROLE OF CHROMOSOMES AND HORMONES
So, the two aspects to the biological approach we need to consider are chromosomes and hormones,
they are of course connected, with your genes coding for the levels of hormones
your body produces, but we could be asked about them separately and their roles in both sex
and gender so I’m going to make sure I cover that.
Most people have 46 chromosomes, they come in 23 pairs and are made of long
strands of DNA. They are found in the nucleus of your cells.
Because they are made of DNA, chromosomes hold your genetic information your genotypes,
these code for physical and behavioural characteristics that we call phenotypes.
If we want to explain chromosomes' role in biological sex then that is fairly clear cut.
Most, but not all people fall into XX = as biologically female and XY as biologically male.
These chromosomal differences lead to biological differences,
for example testes develop in males, triggered by a sex determining region on the Y chromosome.
These testis produce high levels of testosterone leading to additional secondary sex differences.
When we come to chromosomes role in gender, things become
a little more contentious. The genetic differences between biologically male and female
chromosomes create a range of biological changes in things like hormonal and neural differences
that then go on to influence the expression of sex typed gendered behaviour.
So how does this happen, well we need to explain hormones.
They are biochemical messengers that travel in the bloodstream. The organs of the body
respond to the presence or absence of these hormones, altering their function.
It's likely you are aware of Testosterone. It’s what is known as an androgen,
meaning a male sex hormone. females do have testosterone,
but the levels are usually around ten times less than what we find in males.
Its role in sex starts early, the SRY gene at around seven weeks
triggers the development of testis and stops the development of ovaries. The developing testis
then start to produce testosterone. As males reach puberty the presence of testosterone is
responsible for secondary sexual characteristics like larger muscles in adult males.
As for testosterones role in gender, it is thought to be linked to the
increased levels of aggressive and competitive behaviour in males.
Oestrogen is the female sex hormone,
again found in both males and females, but Oestrogen is in much higher levels in females.
One of Oestrogens role in sex is the regulation of the menstrual cycle
and the development of female secondary sexual characteristics. Oestrogen is thought
to have a behavioural influence over feelings of irritability and levels of cooperative behaviour.
A final hormone linked to sex differences is oxytocin generally this is produced in higher
quantities in females, but during sex its produced in the same amounts. It stimulates lactation in
females, and it is thought to produce caring and attachment feelings, important for development
of caring behaviours towards infants, but also in developing attachment in couples.
# THE ROLE OF CHROMOSOMES AND HORMONES - RESEARCH EVALUATIONS
If we are suggesting that gender is a biological process, then we
can use biological evidence for A-typical gender development to support that claim.
A-typical gender is any individual whose gender identity doesn't follow the statistically typical
male equals masculine female equals feminine pattern.
Another way of butting it is their gender identity doesn’t match the sex assigned to them at birth
These next two evaluations are a little tricky, but we get to use them both for this section,
and for our final video in the unit when we cover A-typical gender development,
so overall fewer evaluations to remember.
The first by Van Beijsterveldt looks at genetic evidence, using a very large sample of over 8000
twin pairs in the Netherlands, so these were either dizygotic, sharing half their genome or
monozygotic, so genetically identical. The mothers of these twins were questioned about their gender
identity. When they looked at the data, the genetic difference between MZ and DZ twins
accounted for 70% of the variance in gender identity. This supports the idea that information
coded within chromosomes does influence gender identity. Meaning gender is heritable.
Another interesting aspect of this work was the data showed that little girls with a female co
twin were actually more likely to show cross gender behaviour than those with a male co twin.
The researcher points out, this is the opposite of what we would expect if we wanted to explain
gender with social learning theory, as we would expect the little girls with bothers
to use them as a role model and imitate their male gendered behaviour.
So actually, you could technically use this evaluation in three sections,
I don't include it in the social learning theory video,
but this would make an interesting critical evaluation of the ideas we cover there.
A recent study by Theisen combines evidence for theories on genetics and hormones. This study
was a complete analysis of the genetic material, so chromosomes, of 13 transgender individuals.
This data was compared to the data held on 88 non transgender controls. The analysis identified 21
gene variants that are involved in oestrogen reception in areas of the brain that before
birth become sexually dimorphic, so they are different between biological males and females.
So, what is that telling us? Well first of all that oestrogen seems to have a role to
play in producing sexually dimorphic brains, potentially leading to gendered behaviour.
and that genetic variations may be resulting in variations in gender identity.
Now of course depriving sex hormones or exposing people to high levels of sex hormones
just to see how behaviour changes under experimental conditions would never be ethical.
But these studies have been carried out on animals, its been repeatedly shown that female
rats and mice don't show typical maternal caregiving behaviour if they are deprived of
oxytocin and oestrogen, and that behaviour starts when they are able to produce the hormone again.
Also, male mice that are castrated so no longer produce high levels of testosterone
stop showing typical male biting aggression. But that aggression returns when they are injected
with testosterone. Also, female mice when injected show aggressive biting behaviour typical of males.
THE ROLE OF CHROMOSOMES AND HORMONES
Now those studies are interesting, they seem to show a clear cause and effect relationship between
gendered behaviour and hormone levels in experiments we can’t conduct in humans.
But of course, there is a big question about if we can generalize those findings
to humans. As we will see over the next few videos,
gender in humans is influenced by socialisation from parents, by wider
cultural norms and by our cognitive ability to develop complex schemas to understand the world.
Perhaps some animals like the primates share some of those factors, but most animals don't,
so it's likely not valid to say what we see in animal studies automatically applies to humans.
But one positive of this research is practical applications, understanding the role hormones play
on gendered behaviour could lead to hormonal therapies, say for example for women who are
struggling to pair bond with their infant, or for addressing issues around heightened aggression.
But while we have talked about male and female sex hormones,
to be honest that picture is too simplistic, one example is a form of oestrogen has been
found to be vital in the male sex drive and in sperm production. But this can be treated by
giving what has been traditionally thought of as a female hormone to males with low sex drives.
And a final evaluation is really a point about holism and reductionism. Work by Van Anders showed
that females testosterone levels significantly increased if she did an activity that simulated
having power over another person, it was actually a role play about firing someone from a job.
The researchers suggest that rather than just testosterone leading to male gendered behaviour,
there are also the opposite processes. But we live in a world where men are socialised to
be more competitive and dominant, and women are socialised to be more cooperative. This
could be increasing the relative difference of testosterone between the sexes even more.
A little bit of a tricky evaluation this one, but hopefully you can see
it suggests a valid explanation of hormones' role in gender is likely
a complex interaction between social and biological factors.
ATYPICAL Sex Chromosomes
So I mentioned typically people have either an XX or XY 23rd pair of chromosomes,
but there are rare A-typical variations. Two that we need to cover here are XXY,
a condition called Klinefelter's Syndrome and X0 a condition called Turner's syndrome.
One in 660 males have XXY, they have an additional X chromosome,
but they do develop physically as males, but some physical variations can be less facial hair,
are usually tall with long limbs, smaller than average testis and can develop breast tissue.
There are also some psychological differences, and increased likelihood of cognitive problems like
dyslexia, and can be generally passive, but some emotional problems, like being easier to upset.
Turner syndrome is a much rarer condition affecting around one in 2000 girls.
This is the lack of a second chromosome in the 23rd pair.
This condition interferes with sexual development, and results in a lack of a menstrual cycle,
so females with turner's syndrome are sterile, meaning they are unable to have children.
Breasts don't develop. They have a shorter neck that is sometimes webbed
and look generally immature for their age.
Psychologically they can have a high verbal ability, so reading and writing,
but their visual ability tends to be lower than what would be expected compared to peers.
They may also act immature for their age.
# ATYPICAL Sex Chromosomes GENERAL EVALUATIONS
Psychological research on Klinefelter and Turner syndrome has been important in improving the lives
of these people. This is in part the development of hormone therapies, giving oestrogen to females
with turners around puberty helps to normalise physical development including increasing height.
In the same way males with KS who receive testosterone
develop facial hairs, show increased energy, so less passivity. And the data also suggests the
increased testosterone also improves some of the behavioural and learning problems.
Now clearly research on Atypical chromosome patterns
is helpful in understanding the roles of typical chromone patterns in sex and gender,
but researchers have to be careful of reading too much into the data. These are still very
rare conditions, and the behavioural aspects may not be a direct result of the genetic differences,
for example the fact that girls with turner syndrome are often socially immature may be linked
to their physically immature looks and how other people respond to them because of those looks.
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Outro
Here is a real gender exam question from 2017 on turner’s syndrome and Klinefelter’s
syndrome. Give it a go see how you do. I want to thank everyone who has supported this
channel over on Patreon during the development of the gender unit. You help make the development
of these free A-level videos possible. If you are a psych boost patron at the
neuron level and above you can access 6 bonus gender tutorial videos over on psych boost.com.
In them I will talk you through a model answer for the exam questions,
and I will talk you through some general exam tips based on the examiner reports.
for everyone else don't forget to subscribe so you don't miss
the videos released right up to your exams,
and I will see you in the next psych boost video. Cognitive explanations of gender development.