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01 September 2005

Don't my genes determine my behaviour?

Don't my genes determine my behaviour?

by John Bryant

Imagine a British city centre late on a Friday night. Many of the people spilling out of bars and clubs have consumed large amounts of alcohol. Their actions, speech and perceptions of reality are rather different from what they had been earlier in the day, demonstrating how behaviour patterns and brain functions may be altered by a chemical, in this case ethyl alcohol. We also know of other drugs that alter states of mind lead to behavioural changes, some of which are prescribed medically, such as for depression or anxiety.

As we study brain function we are learning more about the biochemical aspects of nerve conduction, mood and the state of wakefulness. We also understand that there are specific recognition mechanisms within the brain for different biochemical molecules. Indeed, some drugs, including certain prescribed pharmaceuticals, actually disrupt or alter the recognition and subsequent 'use' of particular biochemicals in the brain.

Which leads us to think about genes. Specific genetic activities are needed to enable the cells to manufacture not just the brain biochemicals but also the molecules involved in their recognition and use. This then leads us to suggest, quite correctly, that genes are involved in brain function and in behaviour. We also note that certain types of brain injury lead to dramatic behaviour and personality changes, emphasising that aspects of mind and behaviour are related to the physical structure and organisation of the brain.

Genes for this and that

It's easy to believe in a 'gay gene', a 'violence gene' or even an 'infidelity gene'. Unfortunately, none of these genes exists.

In general then, scientists agree that genes influence human behaviour. However, it is wrong to assume that our behaviour is genetically determined. There are two reasons for saying this. First a general philosophical one: it is a mistake to adopt the naturalistic fallacy that a physical description of a phenomenon is the last word, that there is no need for any further explanation. Sadly, the naturalistic fallacy finds its way into many people's thinking, not least because of pronouncements of scientists like Richard Dawkins, who claims we are simply the product of our genes.

This myth also finds expression in phrases like, 'Surely science has disproved God: Science can do no such thing. It does not have any authority in the realm of the spirit. What science does is to provide a description of the physical nature of the universe. Christians working in scientific fields believe this gives us glimpses of the Creator's handiwork - a privilege indeed.

The second reason for challenging genetic behavioural determinism is that the scientific data do not support it. The expanding science of behavioural genetics essentially supports the idea that human behaviour is influenced by genes. However, behaviour is also influenced by environment, including social factors, and by experience. Possible interactions between these factors and genetic activity are very complex. What this means is that we cannot make a one-to-one correspondence between a behavioural or personality trait and the activity of a gene.

Yet the media love to tell us otherwise. It is simple, it makes a good story, it is relatively easy to understand that there is, for example, a 'gay gene', a 'violence gene' or even an 'infidelity gene'. Unfortunately, none of these genes exists, but the media continue to produce such statements: they have adopted naturalistic reductionism in respect of human genetics.

Not just genes

There are many examples that show limitations of the genetic approach. The first concerns connections between nerve cells (neurones) in the brain during development and throughout life. Although genes certainly specify the structural and biochemical components of the neurones, they cannot specify which connections are made; the number of possible connections is simply too great. Further, connections are being made and un-made throughout life, based on learning and other experiences.

Occlusion of an eye early in life, for example, will lead to a lessening of connections between the optic nerve and the brain. On the other hand, new learning experiences lead to new connections being made. In people who become addicted to internet pornography, for instance, there is evidence that the addictive behaviour becomes 'wired' into the connections of the brain. A pair of identical twins with identical genetic makeup, one an addict and one not, have different 'wiring' patterns in the relevant region of the brain.

Finally, taking an example from social psychology, there is extensive evidence that behaviours involved in poor parenting or in abusive relationships are learned from the experience of the person concerned.

But if we stop here we are in danger ourselves of being seduced by the naturalistic fallacy that humans are just products of their genes and of the interactions of their genes with the physical and social environment. Interestingly, even the most extreme proponents of the 'nothing but our genes' view find it impossible to live with their theories. Dawkins suggests that it is the privilege of humankind to be able to override our genes, while consciousness expert Daniel Dennett writes about the 'evolution of human free will'. And of course it is free will, including the ability to make moral judgements, that Christians recognise as one part of being made in God's image. We recognise that the image is marred in us and that our behaviour does not match up to God's standards. However, we also rejoice that through Jesus Christ, and by the sanctifying power of the Holy Spirit, inner change is possible. We have seen it through the generations, we have seen it in other individuals, we have seen it in ourselves. We need not be trapped in particular behaviour patterns because of our genes, our environment or our background: Christ has set us free.

Christians in ScienceJohn Bryant

  • John Bryant is Professor Emeritus of Cell and Molecular Biology at the University of Exeter and Visiting Professor of Molecular Biology at West Virginia State University.
  • To find out more, see Life in Our Hands by Bryant and Searle (IVP, 2004) and Reason, Science and Faith by Forster and Marston (Monarch, 1999).
  • For resouces, links and support, visit www.cis.org.uk
  • Image Credit: Svilen Milev (www.sxc.hu/profile/svilen001)

Part of the Big Question series first published in idea magazine between May 2004 & July 2007