#T03 Beware the “either or” of binary thinking

a baby learning
a baby is learning about her world

Learning to understand the world

From our earliest days, we try to make sense of the world by dividing it up into categories:

me/not me, safe/not safe/, dog/mum

and so on.

These are called “binary” categories, because everything has to fit into one of the two choices.

“Would you like tea or coffee?” forces you to choose one of the categories.

You might prefer milk, but you can’t have it, because it is not available to you.

Binary categories are how we navigate people and things in the real world.

We use categories like:

like/dislike, good/bad,  hungry/not hungry, day/night, presence/absence, ill/well.

Binary thinking is quick and easy.

To survive we need to think quickly and easily about our world. However, binary thinking also oversimplifies the world.

Unless we live on the equator, day/night are not discrete binary categories. Twilight blends day into night; sunrise gradually turns night into day.

The same is true of many other supposedly binary categories.

Type two diabetes can show a range of symptoms, from mild to severe.

So can depression and  conditions like autism, dyslexia and bipolar disorder.

Thinking about spectrums

We are learning to talk about these conditions in terms of spectrums. The analogy comes from the light spectrum:

there is a continuum of wavelengths of light, each associated with a particular colour

The wavelength of light increases continuously from left to right from about 380 to 780 nm.

The colour changes imperceptibly depending on the wavelength.

We can use the spectrum to distinguish obvious landmarks such as red or blue.

Recognising the exact shade of red or blue is much more difficult.

Traditionally, genetics has been built on binary thinking.

Its founding father Gregor Mendel studied differences in pairs of contrasting characters.  Such as tall/short pea plants or round/wrinkled pea seeds.

It is easy to think that everything is like that.

In fact, everything is not like that.

In a population of individuals, most characteristics vary continuously from the minimum to the maximum.

Think of human height,  it is more like a spectrum than a binary category. Individuals can be any height, rather than just being either tall or short.

#T03 We need to be very wary the “either/or” of binary thinking. 

One of the biggest pitfalls of binary thinking,  is the binary category of nature/nuture. This is causing real problems in our contemporary thinking on genetics.

Of this, much more, later.

#T02 Genes are generalists

The Jim twins
The Jim twins – identical, but separated at birth.

The fascination of twins

The 1980s were the golden age for twin studies. Identical twins share the same DNA, because they come from the same single fertilised egg.

Some pairs of twins were (sadly) separated at birth to be adopted into different families. Many did not know they were twins until they were adults.

Separated identical twins are a natural laboratory for studying the effects of genes and the environment on behaviour.

Thomas Bouchard studied such twins in the University of Minnesota. One pair, both called Jim, became international celebrities.

The Jims were remarkably similar, enjoying maths and carpentry at school, but not spelling. They both married  women named Linda and then Betty.

The Jims both had a child called James Allan.

They both worked in the security business, both drove a Chevrolet, and both chain smoked the same cigarettes. Their families took holidays on the same beach in Daytona at the same time of year.

The conclusion drawn was that their genes were somehow producing these behaviours and that there had to be many genes to produce such specific effects.

How many genes are there?

I remember being in seminars where these (and other similar) findings were being shared. This was “cutting-edge” science and we were caught up in the enthusiasm. One (now very) eminent geneticist speculated that there had to be at least 250 000 human genes.

The idea was that one (or more) genes somehow caused each of these characteristics. Jim and Jim were machines built by their genes.

We no longer think like that. The Human Genome Project reported that there were 30 000 genes; now we think it is nearer 20 000. There are fewer genes than there are human proteins, so the old idea that one gene produces one protein is also wrong.

Furthermore, the idea that there are genes “for” choosing a type of car or a wife by her name or a beach to holiday on is also redundant.

Genes shape personality but only in very general ways, probably through their effects on brain development and the actions of  nervous systems.

So, the second tool for clear thinking is:

#T02 “Genes are generalists: they only have an indirect effect on the development of characteristics.”




#T01 Geneticists usually study differences between people

How DNA is organised in your cells. Image by: Eukaryote_DNA.svg

Vivre la différence!

I remember my professor saying that the science of genetics would not exist if all humans had the same genetic information.

These days, we measure genetic information in terms of the pairs of bases that make up the double stranded DNA molecules.

What is DNA and why does it matter?

DNA is a chemical found within chromosomes, in each of our cells.

There is an identical copy of the DNA in each cell.  It was brought together when your father’s sperm fertilised your mother’s egg.

There are 3 billion pairs of DNA bases in each of your reproductive cells, organised into 23 chromosomes.

There are twice as many pairs of DNA bases in the other cells of your body. This because you receive DNA from you father (through his sperm) and your mother (in her egg).

These cells have 46 chromosomes, made up of 23 pairs.

Most of the DNA bases are the same in everyone. This should not surprise us.

DNA helps the cells to produce the proteins needed to keep us alive.

Our bodies work in much the same way, so we would expect the DNA bases involved in keeping us alive to be the same, too.

Geneticists can only study the 3 million DNA base pairs that differ between us. This is only 0.001% of the total number of base pairs.

Between and within

When geneticists say that a characteristic like height is about 75% genetic and 25% environmental, they are talking about differences in height between individuals in a population.

(In this case, a sample of adult females from Finland.)

They are NOT talking about the relative importance of genes and the environment in the development of your individual height.

The emerging science of epigenetics now allows scientists to study changes in how our cells use our DNA across our lifetimes.

They still study differences, but this time they are changes that occur within us as we grow and develop.

Studies like this are important, but they are relatively new.

So, our first tool for clear thinking is that:

#T01 ‘geneticists usually study differences between people and not within them.’ 

We always need to check exactly what geneticists are talking about, when they present their evidence and we must not confuse ‘between’ and ‘within’.



Tools for clear thinking

Waddington's book cover
A little book, but full of ideas

One of the thinkers that has had the biggest effect on me was Conrad H. Waddington. Waddington died in 1975, a few months after his “Evolution of an evolutionist” was published. I remember picking it up at school and starting to read the opening chapter and not understanding a word of it. But I was very intrigued!

Later, at college, I read more Wad, and became interested in how genotypes interact with environments in plants. At that time, studying it in in humans was not possible. These days, it is.

I eventually became Head of Science in the secondary school where Wad was educated and began to discover the extraordinary story of his schooling, which helped to shape his thinking for the rest of his life. I have written about this, and I have two papers coming out in School Science review next year that explore his thinking further.

Waddington’s was revising ‘tools for thought’ when he died. It was published posthumously in 1977.

His tools for thought are partly philosophical and partly scientific. They are ideas that are expressed simply, without a “lavish decoration of technical jargon”. As he said,

“any idea that is going to be really useful…can, after adequate time to digest it, be put into reasonably simple language.” (p.xii)

That is the challenge for this blog – to identify tools that can help us think more clearly about the possible futures that an understanding of evolution and genetics could bring. Then we can decide what our (and society’s) responses should be. We will not agree on these, but may be we can agree on the ideas that are most important to us. Who knows? We shall see.

It’s boom time for genetics – is that good for us?

a genome map
A genome map. Can it be read like a crystal ball?

It’s boom time for consumer genetic testing with the whole world and her dog getting it done.   If it’s only a bit of fun, where is the harm in that?

The reach of genetics is expanding and its influence is powerful. It is already established in our health and medical wellbeing. Whatever will be next?

The new genetics could influence our our sense of identity and our attitudes to education. It will lead us to question our understanding of diversity, including race and gender. 

History shows that genetics’ attempts to do this in the past have largely been unsuccessful and sometimes dangerous. How can we make sure that the future is different to the past?

What impact should advances in genetics have on our lives, the lives of our families and on our communities?

How should we plan so that we can reap its benefits, whilst being protected from its dangers?

Can the new genetics affect how we see ourselves in the world?

This blog tries to give us some tools for thinking, so that we can develop rational attitudes and make considered decisions for the welfare of ourselves and our society.

The blog is being written as I prepare to teach a unit on Genetics, Society and Education in the School of Education in the University of Bristol, England, during 2021. I will post here as often as I can.

I will send notifications of updates on Twitter using @NeilIngram1, using the hash tag: #geneticssocietyeducation. There is also a subscription box on the sidebar, if you prefer email notifications.

If you are interested in this subject, then come along and join in the conversation.

Neil Ingram, Bristol, 29/12/19, updated 10/12/20