Genetic Explanations

The Paradox of Declining Female Happiness

girl-depression

A recent UK Department for Education study into the mental wellbeing of 30,000 teenagers found that girls were more than twice as likely as boys to suffer symptoms of mental ill health.  The proportion of girls with anxiety or depression has risen by 10 per cent in a decade.

The study was one of the largest of its kind and involved in-depth interviews with thousands of teenagers aged 14 or 15. It was based on a similar study carried out in 2005, allowing researchers to compare trends over time.

37% of teenage girls had three or more symptoms of psychological distress, such as feeling unhappy, worthless, and unable to concentrate, compared with 15 per cent of boys. Instances of depression and anxiety in boys had fallen since 2005, but risen by about 10 per cent in girls.

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Researchers said that some of the increase could be attributed to “pushy parents” and “peer pressure” but these factors were not wholly responsible.  Also, social media was blamed for putting pressure on girls to lose weight, look good, be popular and achieve academic success.

This decline in female happiness started in the 1970s and was noted in 2009 in a major academic study (The Paradox of Declining Female Happiness):

“By many measures the progress of women over recent decades has been extraordinary.  Given these shifts of rights and bargaining power from men to women over the past 35 years, holding all else equal, we might expect to see a concurrent shift in happiness toward women and away from men. Yet ….measures of subjective well-being indicate that women’s happiness has declined both absolutely and relative to men. The paradox of women’s declining relative well-being is found across various datasets, measures of subjective well-being, and is pervasive across demographic groups and industrialized countries. Relative declines in female happiness have eroded a gender gap in happiness in which women in the 1970s typically reported higher subjective well-being than did men. These declines have continued and a new gender gap is emerging — one with higher subjective well-being for men.”

It seems that this decline in happiness of young women has continued since 2009 and is now resulting in depression.

As this steady decline in happiness has been noted in women since the 1970s we cannot blame social media, modern technology or recent changes in parenting, although they may be contributory factors.  Perhaps we should look at more fundamental changes in the structure of our society since the 1970s instead?

We must remember that all living things are effectively transient life support machines for our genes. A disposable container that passes our genes into future generations.  Genes control the physical characteristics and inherent behaviours in all living things.  There is overwhelming evidence that genes control human intelligence, personality and behaviour.

Evolution has occurred at a glacial pace over the last 3,500,000,000 years. Each tick of the evolutionary clock is about 250,000 years, so we are very similar to our ancestors of 50,000 years ago.

Women have a much lower reproductive capacity than men and must carefully nurture the few children they can have to get their genes into future generations.  The evolutionary pressures on men are different.

Over the last 3,500,000,000 years of evolution our genes have finely tuned their life support machines to act in their best interest.  When they need food they make us hungry, when they need water they make us thirsty.  When they need to reproduce they make us impassioned.  When they need to maintain copies of themselves in future generations they make us altruistic and nurturing for our children and grandchildren.

We are rewarded psychologically for good behaviour.  The satisfaction of a good meal, the pleasure of slaking a fierce thirst, the warm afterglow of sex. The radiance of a young woman with a new baby.  The pleasure a mother gets seeing her children happy, fed, clean and healthy. All are incentives to help our genes survive.

We are also punished psychologically for bad behaviour. The misery of following a life-course or career for which we are not suited or does not increase our reproductive capability. The unbearable guilt of perceived poor parenting.  The desperation of a childless woman towards the end of her fertile years.  All are disincentives to act against the interests of our genes.

In the modern, gender neutral, politically correct world we sometime forget what makes us happy.  And very often it is the simple things in life. The things the last 3,500,000,000 years has evolved us to do.

Perhaps in order to feel happy and fulfilled we should play the game.  We only get one shot at life.  Perhaps we should listen more to our bodies and less to politically correct ideology?

So perhaps this unhappiness is caused by women trying to be something for which they had not evolved?  Perhaps the creep of feminism since the 1970s is a contributory factor?  Perhaps women are not getting the necessary psychological rewards in a modern, gender neutral, politically correct world?  Perhaps the “sexist” 1960s philosophy was right.  Many women just want to get married and have babies.

Genetics works on a population level and cannot be used to make predictions about individuals.  However, the decline in female happiness since the 1970s occurs on a population level.

Anybody seriously interested in the happiness of women must consider all possibilities.

References:

The Paradox of Declining Female Happiness (academic reference)

Further reading:

Feminism, childlessness and female unhappiness – an evolutionary explanation

Men and Women Evolved with Conflicting Interests – why we don’t always get along

 

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Genetic Explanations

Intersex, hermaphroditism and evolution.

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“Intersex” is a modern term for hermaphroditism.  It is used to describe a variety of conditions in which a person is born with a reproductive or sexual anatomy that doesn’t seem to fit the commonly accepted definitions of female or male. For example, a person might be born appearing to have a female on the outside, but having mostly male-typical anatomy on the inside. Or a person may be born with genitals that seem to be in-between the usual male and female types.

There are signs of intersex issues filtering into mainstream life in the same way that transsexual issues did before Caitlyn Jenner’s celebrity transition brought them into the limelight.  An MTV teen show, Faking It, features a character who happens to be intersex.  Intersex or hermaphroditism has been long recognised as a medical condition since ancient times.  What may have changed is society’s recent better acceptance of an indeterminate sex.  Or rather re-acceptance, as indeterminate sex was better accepted in ancient times – along with other un-modern concepts such as eunuchs.  It makes sense to allow an intersex individual to reach puberty before letting them make an informed choice regarding their body’s sex.  We know that the sex of their brain will make a big difference to the sex they will choose their body to be.

The development of the human body and brain into the sexes is a complex process.  This includes the interaction of genes, hormones and environmental factors (e.g. disease, drugs and pollutants) at different times during our development in the womb, immediately after birth and during puberty.  Variations in this elaborate process can cause brain development and body development to fall outside our commonly accepted ideas of gender.  For example a male brain inside a female body (or vice versa) and indeterminate sex organs. To this extent what we currently call “transsexual” and “intersex” have a similar root cause.

In terms of evolution it is important to understand that nature has no intent.  Evolution is not sentient and not trying to be anything.  Evolution is driven by natural selection and to work its magic it needs variation from which to choose.  Variation is driven by random genetic events.  Intersex individuals are therefore not unnatural and are just part of the evolutionary process that provides natural variation without which life on this planet would have stalled at the single cellular stage.  Of course if the natural variation results in a biological format with a reduced ability to reproduce we would expect their numbers to be low.  And in the case of intersex individuals they are relatively rare –  less than 1 in 2000.

If society is able to accept the modern view of evolution by natural selection then intersex individuals should not feel like freaks but simply as normal individuals who are different to the average.

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Genetic Explanations, Liberty, Politics and Economics, Religion

Why homosexuality is natural – an evolutionary explanation

Since Aristotle, we have philosophised a scientific and moral order to the world.  A “natural order” or “utopia” to creation.  A way things were meant to be.  If we acted against this order then nature would be disrupted and chaos would ensue.  This pre-supposition was incorporated into the major religions where it is assumed that God had a plan for creation and that His plan was “designed” to be harmonious.  If we could only understand what God intended for the world then we would know how to behave. But only religion knew how we ought to behave according to God’s design, because only religion knew God’s mind. Religion therefore got involved with “moral teaching”, which was a code of behaviour that God had intended and endorsed.

So religion expropriated moral behaviour based on a belief in a “purpose” or “design” of nature.  Men were men, and women were women, and they were meant to marry and have children.

However, unlike Aristotle’s assertion and accepted religious doctrine, evolution does not provide an “ought” for nature.   There is no intention in evolution.  Genes have no intelligence or sentience.  They are inert, self-replicating, complex molecules that have evolved over 3,500,000,000 years to build intricate life-support machines around them (living organisms) that help them replicate themselves.  We humans are a disposable container to further the interest of our genes.  We die, they don’t.

Evolution works by natural selection.  Each generation of genes has small random variations and mutations (some beneficial, most harmful) from which nature chooses the best characteristics using natural selection.  The beneficial behaviours survive and are amplified in future generations and the unbeneficial behaviours dwindle or die out.

Genes merely cover their options by providing random variation to ensure that whatever the future environment may be, some of them will be adapted to take advantage of it.

Without this evolution could not occur and we would still be living primordial slime.

So massive climate change, asteroid attacks, disease and any number of previous natural disasters has not wiped out life on our planet.  It just changes which genes (and therefore which species) are best adapted for the new environment.

So there is no “ought” in evolution.  There is no “intent” or a way things were meant to be.

So nature naturally provides variation in human characteristics and behaviour.  We have variations in skin colour, variations in hair colour, variations in aggressive behaviour and variations in intelligence.  And yes, variations is sexuality.  Some people are gay, some are heterosexual, and some can be anywhere on the spectrum in between.  So homosexuality is as natural as red hair or black skin or blue eyes.

Studies have shown that homosexuality runs in families, leading most researchers to presume a genetic underpinning of sexual preference. However, no major gene for homosexuality has yet been found.   But whilst much variation is directly caused by genes, we know that some variation is only indirectly caused by genes.  Recent studies in epigenetics have found a plausible mechanism for human homosexuality.  Epi-marks constitute an extra layer of information attached to our genes’ backbones that regulates their expression. While genes hold the instructions, epi-marks direct how those instructions are carried out – when, where and how much a gene is expressed during development.

Sex-specific epi-marks produced in early foetal development protect each sex from the substantial natural variation in testosterone that occurs during later foetal development. Sex-specific epi-marks stop girl foetuses from being masculinised when they experience atypically high testosterone and vice versa for boy fetuses. Different epi-marks protect different sex-specific traits from being masculinised or feminised – some affect the genitals, others sexual identity, and yet others affect sexual partner preference.

Epi-marks are usually erased and produced anew each generation, but recent evidence demonstrates that they sometimes carry over between generations and thus can contribute to similarity among relatives, resembling the effect of shared genes.  When sex-specific epi-marks are transmitted across generations from fathers to daughters or mothers to sons, they may cause reversed effects, such as the feminisation of some traits in sons and similarly a partial masculinisation of daughters.

So this mechanism can affect a developing foetus’ response to hormones in the womb which may affect brain development and sexuality.  But how can a genetic trait that causes sexual preferences which will not result in pregnancy and children survive generation after generation?   The reason that many people think homosexuality is “unnatural” is because it denotes behaviour which does not result in any future generations.  Natural selection should ensure that genes for homosexuality will die out.  Many believe the fear of persecution caused many homosexuals to marry and have children in order to fit into society, thus propagating these genes into future generations.  However,  mathematical modeling demonstrates that genes coding for these epi-marks can easily spread in the population because they only rarely escape erasure causing homosexuality in the offspring.  Genetic transmission of epi-marks between generations is the most plausible evolutionary mechanism of the phenomenon of human homosexuality.

So our knowledge that homosexuality has a genetic basis, which is subject to evolution by natural selection, would lead us to predict that homosexuality would be rare.  This is verified by the  results of the third National Survey of Sexual Attitudes and Lifestyles recently published in The Lancet.   It shows that 7% of men have had some sort of same-sex “sexual experience” and only 4% had physical sex with a man.  The percentage of females who say they have had a sexual “experience”, including kissing, with another woman was 16% and the number admitting to having sex with another woman was 8%.  However there are good evolutionary reasons why we would predict that homosexual behaviour in women would be greater than in men.  (See blog:  Is there a bit of lesbianism in all women? )

Now that homosexuality is accepted in modern societies there is less pressure on homosexuals to marry and have children in order to “fit in” and avoid persecution.  This could mean that there will be less homosexuality in the future because if there are genes which code for homosexual behaviour they would become even less common.  However the recent research into epi-marks suggests that homosexuality will never disappear.  It will just remain rare.

Gay Marriage and Liberty

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Genetic Explanations

If 50% of the differences between our personalities and intelligence is Genetic, is the other 50% Nurture?

It is always wise before getting involved in a discussion of genetics and human behaviour to say a number of things up front before launching into a confusing analysis. I’ll argue that in the developed world nurture makes little difference to who or what we are.

  1. Evolution and genetics does not care a jot about human happiness, fairness or equality.  Evolution’s only driver is to successfully reproduce genes and move them forward in time inside the cosy environment of a living organism (e.g. us). We are a disposable container to further the interest of our genes.  We die, they don’t.
  2. Any behaviour endowed by the genes, which make us more likely to survive and have more children, will by definition cause more of that type of behaviour to be inherited in the subsequent generation.
  3. Evolution moves along at a glacial pace.  One tick of the evolutionary clock is approximately 250,000 years.  We are therefore very similar to our ancestors of 50,000 years ago.  Recent technical and social advances are largely irrelevant to our genetic make.
  4. Evolutionary genetics can go a very long way to explaining human behaviour.  Each species is hard wired to behave in a very specific way and this has been shaped by the mechanism of evolution my natural selection.  i.e. it explains the is of human behaviour.
  5. Any discussion about the ought of human behaviour cannot and should not be decided (or justified) by evolution.  Morals, ethics, the rule of law and civilised, evidence based debate are the only mechanisms for reaching a consensus of how we ought to behave.
  6. For evolution to work there needs to be variation in behaviour so that natural selection can do its work.  Each generation has random variation and mutation (some beneficial, most harmful) from which to choose the best characteristics using natural selection.
  7. That said, I believe the human species evolved as a social, altruistic species and it is very much in our interest to act in this way.

Much of the work on genes versus environment (nature vs. nurture) has relied on identical twin studies and adoption studies.  Identical twins share identical genes, so it is very useful to follow the progress of identical twins that have been separated at birth and brought up in different environments.  In this way we can measure the effect of genes, irrespective of environment.  This type of study can be compared with adoption studies, where we can compare the life of a child brought up in a specific environment, which is very different to that of their genetic parents.

There is an enormous amount of data from these studies, which are now backed up with studies of Molecular and Mendelian Genetics.

The conclusion is that at a population level, on average, something like 50% of the differences between our intelligence and personalities is genetically determined.  (I’ve laid a trap here for those who believe that nurture is the overwhelming influence in our life.  Careful you don’t fall into it!).

Many people seem to believe that talent (e.g. the ability to hit a tennis ball) may be genetically determined, but drive and ambition is not.  What evidence do they have?  The ability to concentrate, a desire for wealth and power, the desire to be caring and altruistic could be equally genetically determined.  We all know people with talent and no drive, and also sadly, people with drive and no talent.  To be wildly successful we need both.  Can drive and ambition really be learned?

Many other types of behaviour are typically attributed to learned behaviour by flawed sociological studies.  i.e. it is assumed the behaviour is learned from parents or close social group.  e.g. the majority of people who sexually abuse their children were sexually abused by their relatives, implying learned behaviour.  People who smack their children were smacked themselves, implying learned behaviour.  The income of a person is most likely to be predicted by the income of their parents (i.e. as a proxy for talent and drive), implying learned behaviour.  In no cases are these sociological studies investigated for a genetic component.

Individuals inherit genes from their parents.  Could it be that part of the behaviour is inherited through the genes?  i.e. genes for abusive behaviour, genes for violent behaviour, genes for drive and talent…..

Mix our knowledge of genetics with one of the most passionate and time consuming aspects of human behaviour, i.e. finding a mate, and you have a very powerful natural force. Talented, motivated, women generally seek and marry talented, motivated, men. They then generally have talented, motivated children. i.e. they cluster the genes responsible for these talented, motivated characteristics into certain sections of society.  As these characteristics generally lead to higher earning potential they are more likely cluster in the affluent parts of society.  Consequently talented, motivated children are not equally spread in our society, assuming we have a certain level of social mobility.  Remember I’m talking about is not ought.  This process is called assortative mating.  The identical twin / adoption studies have concluded that since the 1950s upbringing makes virtually no difference to our social status by the age of 35.  i.e. society is mobile enough in developed countries.   This makes sense, as any environmental influence is short lived, whereas we have our genes for life.

Now for the trap laid for the nurture lovers.  If 50% of our differences are genetic, then the other 50% must be nurture and open to social and political intervention, right?

The term “genetically determined” is very narrow.  It refers to traits and behaviours which are inherited through the genes.  Nurture is everything else.  For example we know that the hormonal, nutritional and chemical environment of a developing child in the womb has non-negligible effect on its future life.  What was interesting about the identical twin studies was not only what made them the same (their genes) but what made them different.  Identical twins share the same womb, same parents, same wealth, same schools, same teachers and are still different.  It is difficult to imagine genes controlling the exact wiring of the human brain as it develops.  Could it be that whilst the overall brain structure is genetically pre-determined, whether a neurone in a developing brain zigs to the left, or zags to the right before connecting with a neighbour is in fact random?  Maybe one identical twin gets bitten by a dog, or catches ‘flu or only gets the bottom bunk bed and these trivial experiences add up to a large difference overall.  Whatever the reason it seems that much of what we describe as nurture is also not open to manipulation by political social policies.

Also, if nurture was a dominant force, all siblings in a family would be the very similar on the basis they share a similar upbringing.  Anybody with more than one child knows that this is nonsense!

Finally to a point on meritocracy.  It is in our interest as a species that we have the best people in the right jobs.  We all benefit.  There should be no discrimination based on colour, class or sex.  But this includes positive discrimination too.  We should not be giving people a leg up because a perceived injustice unless we can prove beyond doubt that they really have been disadvantaged.

Many believe Private schools, well-connected parents and other things too subtle to mention all shape success. Few would disagree that the State has a role to play in dismantling some of these advantages to create a more level playing field.  But the part of nurture that is open to political manipulation is a very  small compared to everything else in a country that is already economically developed and relatively socially mobile.  We must learn to manage our expectations as to how much can be achieved with political meddling.  Unless that State wants to dictate with whom we marry?

Assortative mating ensures that genes for talent and motivation would be clustered in affluent parts of society.   However this is only a tendency.  Vast talent will be found in non-affluent parts of society because there are many more of them.  History tells us that well meaning meddling by the State merely consumes vast financial resources with no benefit, partly because we try to save everybody.  We would do better to spot talent and motivation early and nurture it, wherever it comes from. Concentrate our resources where we can make a difference.  i.e. targeted State intervention.

Who we are and what we become in a socially mobile, developed society seems to be a mixture of genes and luck with a little nurture thrown in. The best way to ensure success in life is to choose your parents with great care.  It is unfair.  Remember is not ought.

Further  Listening:

Intelligence: Born Smart, Born Equal, Born Different Three BBC Podcasts on the genetics of intelligence.

What makes some children smarter than others?  Professor Robert Plomin talks to Jim Al-Khalili about what makes some people smarter than others and why he’s fed up with the genetics of intelligence being ignored.

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Genetic Explanations, Liberty, Religion

From where do we get our moral behaviour?

Since Aristotle, we have philosophised a scientific and moral order to the world.  A “natural order” or  “utopia” to creation.  A way things were meant to be.  If we acted against this order then nature would be disrupted and chaos would ensue.  This pre-supposition was incorporated into the major religions where it is assumed that God had a plan for creation and that plan was “designed” to be harmonious.  If we could only understand what He intended for the world then we would know how to behave. But only religion knew how we ought to behave according to God’s design, because only religion knew God’s mind. Religion therefore got involved with “moral teaching”, which was a code of behaviour that God had intended and endorsed.

It was consequently assumed that if we did not believe in God then our moral behaviour could not be guaranteed.   If we don’t believe in God what is to stop us murdering and raping?  If there is no retribution after death what is to ensure we live a good life?  Non- religious people were feared, excluded, subjected to violence and sometimes death.  Religious belief was considered the default position.  The term “atheist” is a strange word construct that confirms this thinking.  We are not normally described as something we are not.  We are not non-socialists, or non-Manchester United supporters.  Only non-believers.  In past times atheists would have been advised to play the game, go to church and pretend to believe in order to avoid persecution.

So religion expropriated moral behaviour.

But mankind is moral and ethical in the absence of religious belief.  There is no evidence that religious people are more moral than atheists. Or that they are more law abiding. In recent polls, 65% of British people said they weren’t religious and weekly church attendance in the UK is down to less than 2%.  No massive crime wave has ensued.  Violent crime is at a 30 year low.

So if it not religion, where do our morals come from?

Interestingly there are a number of psychological tests which can elucidate our moral compass i.e. establish what moral beliefs we all hold.  These tests can be applied to people from all different cultures and belief systems.  From these tests we can demonstrate that mankind shares an innate moral code, independent of religious indoctrination or cultural teaching.  This moral code is hardwired in the same way as much animal behaviour is hardwired.  It is part of human nature.

Most humans would feel bad about causing harm to another person. We would generally feel revulsion at seeing a child raped or an innocent murdered.  We feel compassion towards small, vulnerable children.  We look after our sick and dying.  We evolved as an emotional, social, altruistic species (but who admittedly can turn violent if threatened).  These behaviours of nurture, collaboration, teamwork, empathy and compassion have led to our success as a species.  Altruism works in evolutionary terms if an individual of a species has a reasonable chance of it being reciprocated.  This is the “is” of human nature.

However, unlike Aristotle’s assertion and accepted religious doctrine, evolution does no provide an “ought” to human behaviour.   There is no intention in evolution.  The Universe was not meant to be a certain way.  There are just random behaviours encoded by our genes that lead to us to be more or less successful in propagating our genes into the next generation.

Evolution occurs by the process of natural selection.  The beneficial behaviours survive and are amplified in future generations and the unbeneficial behaviours die out.

So it seems that our moral code actually has a Darwinist origin, not a religious origin!

Combine this force of nature with our intelligence as a species and our ability to learn, anticipate and interpret our environment and we have very complex “human” behaviour (a “culture”), which in developed countries now includes evidence based debate, democracy and the rule of law.  This is where we must derive our “ought” of human behaviour i.e. how we should behave.

If we combine our innate moral code with rational, evidence based debate, democracy and the rule of law we have a functioning society. A “civilization” that can even accommodate a few immoral miscreants that the variation component of the mechanism of evolution by natural selection throws up. Our intelligence as a species has allowed us to plan and control our own society.  Most of us have the ability to see how things would be if we allowed anarchy to predominate, so we work hard to create order, security and welfare.

So, we have an inbuilt, genetic, emotional behavioural code and a derived behavioural code from our experience and interaction with our environment.  Some things just feel wrong. Some things we rationalise as wrong.  Some of these emotional and rational codes we choose to call “morals”.

Religion was once beneficial.  It was a good way of creating social control through its teaching and threats of social exclusion and eternal damnation for those that misbehaved.  But now we have the ability to collect real evidence through scientific methods for our evidence-based debates.  We now have good-enough democracy and adequate rule of law.  We have superseded religion.

The negatives of religion are now outweighing the positives:  Illogical, irrational thinking; superstition; religious discrimination; the sinister underpinnings of Islamic Jihad and the barbaric treatment of women are all part of the same belief system.  The same irrational belief system underpins extreme Islam and the benign Church of England. If we condone one version, we must condone them all.  We can no longer claim that we should believe in an untruth (religion) because it is beneficial.  The balance has changed.  We must now free ourselves from the shackles of religious indoctrination.  As Steven Weinburg famously said, “with or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion.”

We are right to challenge religious beliefs in order to create a better, more moral, more rational, fairer and more equal world.

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Genetic Explanations

Men and Women Evolved With Conflicting Interests – Why We don’t Always Get Along

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For millennia human kind has believed in a “natural order”, or a “utopia” to creation.  A way things were meant to be.  Since Aristotle we have envisaged a scientific and moral order to the world.  If we acted against this order then nature would be disrupted and chaos would ensue.  This pre-supposition was incorporated into the major religions where it is assumed that God had a plan for creation and that plan was designed to be harmonious.  Consequently men and women are “designed” to live together in perfect harmony – if only we could work out how!

Darwinism, whilst accepting that men and women have many areas of common interest, also accepts that they will have areas of conflicting interest.

First let’s review the fundamentals of Darwinism:

  1. Evolution is not about survival of the species (e.g. humans) it is about survival of the genes. We are a disposable container that has evolved to ensure genes get moved forward in time. We die. They don’t.
  2. Any behaviour conferred by the genes, which increases the likelihood of having more offspring in any species, will ensure more of those genes are passed to the next generation.  Consequently that “successful” behaviour is propagated and amplified.   This is a natural selection of “beneficial” genes.
  3. Evolution moves along at a glacial pace.  One tick of the evolutionary clock is approximately 250,000 years.  We are therefore very similar to our ancestors of 50,000 years ago.  Recent technical and social advances are largely irrelevant to our genetic makeup.
  4. Evolutionary genetics can go a very long way to explaining human behaviour.  Each species is hard wired to behave in a very specific way and this has been shaped by the mechanism of evolution by natural selection.  We don’t behave like cats or horses.
  5. For evolution to work there needs to be variation in behaviour so that natural selection can do its work.  Each generation has random variation and mutation (some beneficial, most harmful) from which to choose the best characteristics using natural selection.

Our male and female ancestors have had very different evolutionary pressure over the previous millions of years.

Human females have a pathetic ability to reproduce, having no more than a dozen pregnancies in their lifetime. Each pregnancy is life threatening and she will generally only produce offspring one at a time.  Human children are unusually vulnerable in infancy and take many years to reach maturity.  Women therefore engage in a long, energy sapping and life threatening investment in their children to ensure these (few) offspring reach childbearing age.  She must choose her mate with great care to ensure her offspring receive beneficial genes from the father, which in turn maximises the chance of her own genes prospering in the next generation.  It also means she must carefully and selflessly look after the few offspring she manages to produce. She (i.e. her genes) has no other choice.  Women evolved to be more nurturing.

Human males produce 250,000 sperm every second and their number of offspring is limited only by their opportunity to impregnate willing (or unwilling) females.   Two strategies would work to increase the number of their genes in the next generation.  1. Look after their offspring, nurture them and ensure they reach child bearing age (copy the only strategy available to women). 2. Spread their sperm as far and wide as possible, have thousands of offspring and hope that some reach childbearing age.  A third alternative is the best.  Do both.  Men invest almost nothing in child rearing so it makes sense for them to take huge risks to have the opportunity to reproduce.

Women will choose high social status men (a proxy for good genes) to ensure her own genes have a good chance of survival in future generations.  To prove high social status takes a bit longer so women tend to go for successful, older men (4 years older in the UK on average).

Men are programmed to advertise their success and achievements in order to attract a high social status mate.  Men will choose young, healthy, fertile (read attractive) women because their chosen mate primarily needs to be fit to survive 9 months of pregnancy and the years of childcare that follows.  Men have evolved to visually select a mate on this basis.  Women have evolved for millions of years with this pressure.  Women are therefore programmed to try to look young and attractive in order to find a suitable mate.  Much of this behaviour is hard wired, as is our sexuality and our urge to have sex with attractive members of the opposite sex.  Women also need to recognise these traits in their competition (other women).  Women easily know if another woman is attractive.

So whilst men and women have a mutual interest in looking after their mutual children, there are areas of conflicting interest.  As women can have few offspring it is in her genes’ interests to ensure the father spends all his time and energy looking after her children.  She will also feel an overwhelming urge to nurture her children.  Her genes have no other choice.  The father’s genes’ interests are better served by spending much of his time seeking different partners – particularly young, healthy and fertile (attractive) partners.  Women are more likely to seek commitment from a mate.  Men are more likely to be reluctant to give it.  Men will prefer younger sexual partners which over time act against the interests of his initial, older partners.

But some women are very attracted to totally inappropriate men who clearly act against her own interest.  The handsome, philandering, unreliable, lovable rogue.  Why?  Consider the scenario where a high social status male has a child with a particular woman and then leaves her and philanders his way around the world irresponsibly having hundreds of children with other women.  This is not good for the woman or her child.  But if this woman has a son which survives and inherits his father’s behaviour she will get many more of her own genes into future generations.  About 8% of the men in a large region of Asia have Genghis Khan’s Y chromosome.  He clearly had many willing and unwilling sexual partners.  However any woman’s genes attached to his will have prospered (particularly down the male line), even if the woman herself didn’t.  This is a good example of  a woman having different interests to men (she wants commitment and the man doesn’t).  It is also an example of a woman having different interests to her own genes – it is in her genes’ interest for her to be attracted to unreliable, philandering men, perhaps by convincing her that she will be the only one who will tame him and make him exclusively her’s!  The old adage seems to ring true – women marry men expecting them to change, and they don’t.  Men marry women expecting them not to change, and they do.

We have good evidence that men will generally find a woman less attractive if they find out she is in a sexual relationship with another man.  Women generally find men more attractive if they are attached (and therefore presumably attractive) to another woman.  Her genes will recognise that he may be a good bet in propagating themselves into the next generation because if one women finds him attractive then others might too. These characteristics are in the mother’s genes’ interests if they have a son together and the son inherits his father’s characteristics.  Again this behaviour is very much in the genes’ interests but may be against the interests of their host (the woman) .

This also may explain why many cultures favour sons over daughters.  No cultures favour daughters.  Sons are a much better way of getting lots of your genes into future generations than daughters – whether you are a man or a woman.

An interesting question:  would a mother object to a highly promiscuous son?  He would be a route to having more of her genes propagated into future generations.

Nothing here should make us believe we can predict the behaviour of individual men and women.  Also, I’m describing the is not the ought of human behaviour.  The ought of human behaviour cannot and should not be decided (or justified) by evolution.  Morals, ethics, civilised evidence based debate and the rule of law are the only mechanisms for reaching a consensus of how we as individuals ought to behave.  Evolution is about survival of our genes and does not care one jot about human happiness, fairness or equality.

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