Gene for nurture reasserts itself in who humans are

The nature versus nurture debate was perhaps the most bitter of the 20th century.

On one side, extreme eugenics led to the Nazis' ideas of a master race and the Holocaust as they sought to "purify" mankind.

The backlash that followed sought to deny almost any genetic influence.

Even gender - whether you viewed yourself as male or female - was said to be learned socially.

Increasingly, scientists are now unravelling the full extent of the influence of our genes and breakthroughs seem to come thick and fast: a gene for fear, one for depression, another for creativity.

But those who believe these headline-making discoveries are triumphs for supporters of the nature side of the argument should think again.

What makes us who we are is far more complex and the study of "epigenetics" - the way genes are expressed - has thrown up evidence that being cuddled as a young child, what you eat, what the weather is like and even who are your friends can change the way your genes behave.

And it would appear some of these altered genes are passed on to future generations with a range of studies emerging to support the idea:

By looking at the records of harvests, births and deaths in a remote town in northern Sweden, researchers found evidence that famine at a critical time in the life of one person could effect the genes of their grandchildren.

Pregnant women who were near the World Trade Centre in New York on 11 September appear to have passed on the effects of becoming stressed to their children.

Last year, Professor Moshe Szyf and colleagues at McGill University in Montreal showed that if a young rat was not licked and groomed enough by its mother, this altered the way its genes were expressed and the rat grew up to be more anxious than a well-groomed sibling.

This year Prof Szyf's team found that the expression of rats' genes could be changed permanently by giving them a specific amino acid, in work that suggests food supplements could be used to change people's behaviour for the better and even stop the effects of schizophrenia and other brain diseases.

Prof Szyf said: "Yes, you do get an inheritance of genes, but you can change that both ways, by the kind of upbringing you get, the kind of food you eat and experiences you have.

"Epigenetics kind of bridges the gap between the social and natural sciences and raises the idea that people are not to be seen only as individuals but in the context of their community and their environment.

"That's completely different to what we have done previously when we have reduced humans to cells and genes."

He said that in a way, epigenetics was telling people something they already knew.

"We all know it is important how you raise your children; now we know it also has a chemical impact," Prof Szyf said.

"That puts a certain responsibility on the shoulder of parents. They cannot say 'I've a kid with bad genes'.

"There might be genetic differences between their children that makes one more temperamental, but with upbringing you can erase those differences."

He is predicting a renaissance in scientific thinking as a result of epigenetics and believes it will be "the next big thing" in medicine, with epigenetic drugs already being used to treat some cancers.

New treatments for behavioural disorders, brain and other disease could all be found in drugs that manipulate the expression of genes.

Dr Cynthia McVey, a psychologist at Glasgow Caledonian University, said epigenetics was blurring the divide between nature and nurture, effectively ending the debate.

"What we're seeing is that nurture affects nature and it's impossible to tease them out," she said.

"The epigenetic stuff is very interesting. If you could learn and understand a particular mathematical formula and that changed your brain in such a way, could you pass that on to your children?"

She said in the past the strong belief in the power of nurture had led to some extraordinary theories - such as gender being a product of upbringing rather than genetics.

Dr Ian Jackson, a geneticist at Edinburgh University, has witnessed power struggles in the nature-nurture debate over the past four decades.

"When I was a student in the 1970s, the belief was it was all down to nurture - so people aren't stupid because of their genes, they are stupid because they haven't had the right upbringing and education," he said.

"That was the extreme of the nurture pendulum. It was a sociological idea, but also a backlash against eugenics and the Nazis, their notion that you could classify people as genetically inferior.

"Now it's come back to perhaps a more middle ground. People acknowledge there are genetic influences and environmental forces interact with them."

Steve Jones, professor of genetics at University College London, agreed and was scathing of those who believe genes can be easily linked to specific human attributes.

"The gene for something ... the most dangerous word in genetics is the simple word 'for'. It's much, much more complicated than people worshipping at the shrine of the human genome believe," he said.

Sequencing the human genome was a great achievement, but Prof Jones said it simply completed the study of human anatomy.

"We have now finished dissecting the human being, but a doctor needs more than anatomy - a human being is alive and DNA isn't," he said.

"DNA is stupid because it's a chemical. Chemistry is stupid and biology is smart. Epigenetics is a crucial step in understand how you get from chemistry to biology.

"Clearly the environment is always involved. Every single gene whatever it does is influenced by nurture and every single human attribute is influenced by nature, by genes."

For those brought up in the traditions of the nurture camp, epigenetics offers hope that "nature" extremists are wrong and that we are not born to our fate: pre-destined to succeed or fail, be good or evil.

Dr McVey said: "I think we like to think we have control over who we are. We like to think we have free will.

"I do think it would be very depressing to think that we could not have some impact on our genetic pre-disposition.

"But I do believe we are more than flesh and blood. I'm very much a soul person.

"I discovered that one of my grandfathers had been a minister - I wonder whether it's genetic?"