Nature vs Nurture – genes vs environment

Talk given by Daphna Whitmore at the Marxism Conference in Auckland, June 2008

Every week a new gene is supposedly found for something. This week New Scientist has a headline: They’ve discovered the gene for religion. Dig a little and it’s clear that the claims are grossly inflated. Well, it turns out they haven’t quite found a gene for religion after all, but postulated it exists. The theory is based on a computer programme that predicts that if a small number of people have a genetic predisposition to pass along unverifiable information, that religion will flourish. And this passes for science somehow!

The popular notions of what genes do are interesting.

I caught part of a programme on TV a few weeks ago. It was about people’s behaviours and their sex lives. The participants were asked to record how many times a day they had a sexual thought. The results were a little mixed, but one male had a huge number of sexual thoughts, another male had a moderate number which was about the same as one of the women and one woman had very few. It was a small sample of only about 4 people, so not the most rigorous scientific study. The conclusion drawn by the programme narrator was that “men think about sex more than women, and this is because in evolutionary terms this is an advantage. A woman once pregnant gains nothing from further copulation, whereas a man can keep spreading his genes around to great evolutionary advantage.”

This sort of theorizing is rather typical these days. Yet in the sample there was as much difference between the two men as there was between one man and one woman. But hey, we all know that humans are driven by the need to spread their genes, don’t we? So how do we explain that bizarre anti-evolutionary practice of contraception?

The trouble with many of the crude genetic explanations is that they come about through a series of assumptions and are deeply coloured by social and historical context.

Much of this talk today draws on the work of dialectical biologist Richard Lewontin. He points out that science is a social activity carried out by organisms with a limited central nervous system and severely limited sense organs. It is, moreover, carried out by organisms who have already gone through a considerable period of individual socialization and psychic maturation before they become employed as scientists, in a social setting that has a history that constrains thought and action. The state of science should not be confused with the state of the universe.”

The debate over what influences the development of an organism most – genes or environment – has largely been treated in a mechanical way. The pendulum has swung back and forth as to which plays the bigger role. Right now the pendulum is in the gene camp with all sorts of characteristics being thought to be linked to genes. The problem is most of the genes they talk about have yet to be discovered! (There’s also the “middle ground” types, who are just as mechanical, who say it’s a bit of a combination between genes and the environment.)

A dialectical approach provides a more insightful way to investigate the material world. What is needed is a more careful understanding of the context of the whole organism as well as the environment. Dialectics is a tool to discover and understand the interactions and interconnections.

Dialectics is a method of how to observe and analyse the movement of opposites that are present in all things and processes from beginning to end. From that analysis one can then establish ways to resolve contradictions. It’s not a formula to prove a proposition, it is a tool for investigation.

So I’m going to look at how the pendulum has swung so hard towards genes but also I’d argue that there’s more to development than simply genes and environment.

In the 19^th century there was a debate between the epigenetic school and the preformationist school. The preformationists believed that there fully formed miniature versions inside each sperm which got bigger and bigger, and the egg supplied nutrients to it. The epigenetic school said that was nonsense, that each embryo or organism is gradually produced from an undifferentiated mass by a series of steps and stages during which new parts are added. So which won out?

Surprisingly, the little man idea has prevailed. The idea that genes predetermine everything is a preformationist view. It’s the same as the notion that all the information necessary is in the sperm and egg.

All the information is not already contained in the fertilized egg. There is other important factors in producing an organism. There is a temporal sequence of environment.

As Heraclitus, the Greek philosopher who was a dialectician said “You can’t step into the same river twice”. There is nothing static about the environment.

Timing is a big factor.

Then there is another factor which is indeterminacy from a quantum level to a higher level. It adds a random component and has a profound effect. So much of development is not predetermined, but is uncertain. I’ll go into this more later on.

One key problem is the limitations associated with specialization in science. Today it’s impossible to be a generalist because the body of science so vast, but how do we deal with the isolation of scientists from each other who work in different fields? This has encouraged people to take a narrow view.

GENETIC DETERMINISM

It’s now 55 years since the structure of DNA was revealed and it is time to ask why gene therapy not progressed beyond the trial stage. (There are currently around 100 gene therapy clinical trials aimed toward cancer and diseases such as cystic fibrosis and hemophilia A, infectious diseases – including AIDS – and autoimmune diseases such as rheumatoid arthritis).

The problem is that individual cells in every organism differ enough from each other that no two will process DNA information in exactly the same way, making many genetic therapies impractical and very difficult.

For cancer, for instance, the treatments by and large remain cut it out, burn it off or poison it.

What we find is that DNA doesn’t play quite the determining role that is commonly believed and that genes are irrelevant for some characteristics (eg asymmetry).

The gene-centred view of evolution was popularised by Richard Dawkins who came up with the term the selfish gene. He says evolution acts on genes, and that selection at the level of organisms or populations almost never overrides selection based on genes. He reckons that it’s about genes replicating, not necessarily those of the organism, much less any larger level. Genes are the main thing in the process of natural selection. (Natural selection is the process by which favorable heritable traits become more common in successive generations of a population of reproducing organisms, and unfavorable heritable traits become less common.)

So an almost magical power is ascribed to genes. What’s more there is ‘genomania’ – a frenzied excitement about genes and gene therapy (the ’90s were the decade where it probably reached its height). This has a social context which is holding back progress in science. DNA does reveal a lot, but it is only a part of a bigger picture and must not be taken in isolation.

Heredity involves far more than just genes. Scientists have established that genes are pleiotropic – that is, they convey many messages. The timing and nature of those messages is determined not by them, but by enzymes and other cellular structures that are not genetic.

Conversely, I’m not going to argue though that we are simply, or even largely, a product of our environment. For a start, even our concepts of the environment are shaped by current ideology. “Preserve the environment” is a catchy slogan but nonsense in biology. Lewontin, I think, put the question do organisms “adapt” to their environment or is adaptation a misused metaphor? It bit more on that soon.

We need to take a good look at the social construction of scientific knowledge.

There are various factors which encourage scientists to make overblown claims, (it’s one way of getting funding) and all too often the people who publicise findings are commercially driven to sell papers by over simplifying and sensationalizing.

GENES

There are around 25,000 genes in a human being. Researchers more or less completed the final analysis of the Human Genome Project in April 2003

In 1991 scientists “found the gene for homosexuality” – or so the headlines screamed. They quietly lost those genes some years later when their study could not be replicated. Today there are no known genes for homosexuality.

The mythical gay gene was embraced by various political directions. Gay rights advocates were generally pleased that it was a natural cause, not social, while anti-gays could treat it as a genetic mutation.

What about the risk taking gene?

That was declared discovered, only to missing again. To date there are no genes or set of genes that have been found that relate to any aspect of human behaviour. It’s all purely speculative. But they are still looking!

No one has found the genes for skin colour, height or weight.

Nor has the thrifty gene ever been found. That’s the one Polynesians are supposed to have which is said to make people predisposed to become obese and diabetic once they’ve been in a western society for a few decades. No such gene has ever been found and the geneticist, James Neel who postulated the theory back in 1962 ditched it in 1982. He conducted proper research and found that indigenous people weren’t predisposed – they had normal glucose tolerance tests. He ended up thinking that exposure to a modern diet was the cause, not any gene. Anyway poverty is a much greater marker for obesity than any other factor. It increases the chances by about 50%.

While they are at it maybe they should look for a poverty gene!

If they put as much effort into eliminating poverty as was put into sequencing the human genome the effect on morbidity would probably have been greater.

There’s the thrifty phenotype (phenotype being the appearance rather than the genotype). This is the theory that in poor nutritional conditions, the fetus is prepared for an environment where resources are scarce. If that child is then born into an affluent western environment there is a mismatch. It’s thought that this could last several generations this effect.

Breast cancer genes fair a little better, but not much. To date, most inherited cases of breast cancer have been associated with abnormalities in two genes. But these abnormalities account for only 10% at the most of breast cancers. If one identical twin gets breast cancer, the other’s likelihood of contracting it is only around 10% to 20%. This suggests that genes are not the whole story

There are really only a handful of diseases that have a clear genetic component. Muscular dystrophy, sickle cell anaemia, cystic fibrosis, haemaphilia. There are some other genetic diseases but they are extremely rare.

Around one thousand genetic tests now available to diagnose and assess risk of diseases, and there’s big money in it.

As well as the misguided emphasis on genes, every gene is seen in isolation, certainly in its popular presentation.

This misguided emphasis on genes could be taking away attention from infections as the big killer. Most diseases are caused by infections: cholera, dysentery, malaria, tuberculosis and measles. But they are third world diseases – poverty related. For instance we don’t die from measles in the west because we have adequate protein in our diet. Measles is a protein-consuming disease and can be deadly for people who are protein deficient.

A disease-causing gene that reduces survival and reproduction would normally eliminate itself over a number of generations. One example of this is schizophrenia; patients with the mental illness rarely have children, argues evolutionary biologist Paul Ewald. He thinks schizophrenia may be caused by the Borna virus and argues that this disease would have already been eliminated if it were from a strictly genetic cause.

We know that CJD causes extreme mental illness, and so does syphilis. So it is not such a wild idea that other mental illnesses may be caused by a pathogen not a genetic defect.

So genes are not the be all and end all. Of course, they do play an important role but they are only part of how any organism develops.

ADAPTATION AS A MISUSED METAPHOR

Most people accept that environment does play a role. This is evident when an organism is cloned. It cannot be a simple replica of the parent. For a start it is in a different environment and there is a high degree of uncertainty and random events that result in differences. Evolution is a result of random as well as selective forces. Michael Raglan gives an example of this “Humans, do not have the same fingerprints on their left and right hands and the differences in pattern can be so great that no similarity at all can be detected. Yet the genes of the left and right sides are the same and no usual meaning of environment will allow that the left and right hands of a foetus in its mothers’ womb have different developmental environments”. This is explained at the quantum mechanical – the submolecular level. Quantum mechanics are the physical principles that govern the microworld. It’s this quantum mechanics that accounts for why DNA is a double helix. The H bonds between purines and pyrimidines that are responsible for the double helical structure of DNA. Once again, randomness of the motion of particles is a factor.

History as well as randomness plays a role. Something might have been selected for long ago can influence how organisms take shape later on. An obvious example is our limbs – we have four limbs, not because this is the best possible configuration, but because we are descended from land vertebrates that had fins.

THE NOTION OF EVOLUTIONARY ADVANTAGE

There is a tendency to treat the evolutionary process as one where all aspects of the organism are perfectly adapted to the environment. It’s what we can call optimal adaptation.

This way of thinking assumes every feature must have a benefit for survival. Let’s take skin colour. Actually no one really knows why Europeans are pale, Asians have dark hair etc. Ah, of course, being dark skinned in Africa means you won’t be likely to get skin cancer, one thinks. Indeed that is true. But it doesn’t make any difference to evolutionary survival as skin cancer is something that tends to occur later in life, not during the reproductive years. A more sound explanation, is what Darwin called sexual selection.

For instance, peacocks have large bright feathers, which provide no advantage to flying, and might actually impede flight, thus attracting predators. These spectacular feathers have evolved because they attract potential mates.

People in Europe were attracted to pale faced people and selected them for their mates. That is the current explanation, strange as it may seem. Same thing in Asia – a particular look was favoured and selected for. It sounds weird to us because we aren’t really used to thinking about sexual selection in that way.

The view that we are purpose built for the environment is a notion of an external environment posing “challenges” that successful organisms “solve” those challenges. That is problematic because environments of organisms do not exist before the organism. The physical world exists, but it is not the environment of any organism.

Just as the air we breathe is the result of living organisms, there’s no environment without an organism, and no organism without an environment. Organisms and environment co-evolve. Every organism is in the process of constructing its environment by using it.

Lewontin gives a great example of our boundary layer. Around our bodies is a layer of warm moist air is created by our metabolic activities. We each have our own boundary layer. The wind chill factor is because wind blows away the warm boundary layer. Every organism uses up what it needs and deposits waste products. Plants break up the soil which aids them and other organisms. Fungus grows on a plant and in turn nourishes the plant. Every organism does it at all times. Organisms create and destroy. It’s a symbiotic situation.

It’s not that organisms are well suited to their environment, it’s more that they have interacted and developed a world around them which is suited and which evolves with them at all times. It’s a world in motion, not a fixed world that they enter.

That’s why the notion of “preserve the environment” makes no sense in biology. Every organism has a different environment, its changing with the organism,

And the organism is a unique result of both genes and environment, of both internal and external features, and these are not separate entities. They are a unity and struggle of opposites. It’s not the case that genes determine the organism, which then adapts to the environment. It’s far more dynamic and interconnected: Organisms are influenced in their development by their circumstances and for there part they create, modify, and choose the environment in which they live.

KNOWLEDGE SHOULD ADVANTAGE HUMANITY

No longer should we think of the environment as something unconnected to the organisms that shape and create it out of the raw materials of the physical world.

This perspective enables us to think more constructively so that we can use our knowledge to promote environmental change in a direction that is an advantage to humanity. That sort of ecology is far more appealing than the sort that wants to limit human activity and sees humanity as a blot upon the earth.

Genes are not all powerful. There is a close interaction between genes, environment, and random developmental events. They cannot be separated from the living organism and its realm it inhabits.