So many traits - even very complex social ones - have a detectable genetic influence

Dr Michael Lyons

New Scientist magazine reports that a team from Boston University in Massachusetts compared marriage and divorce rates in identical and non-identical male twins.

They took their data from a registry of male twins who served in the US military during the Vietnam war.

In interviews in 1987 - intended to diagnose mental disorders - some 8,000 of these twins stated whether they had ever married, whether they were still in their first marriage, and if not, how their first marriage ended.

Same patterns

The data revealed that identical twins, who share the same genes, were more likely to follow the same patterns of divorce than non-identical twins, who only share about half their genes.

The researchers say this suggests there is a significant genetic influence on divorce.

But there was no difference between identical and non-identical twins when it came to whether or not they got married in the first place - suggesting this is entirely determined by your environment.

Marriage is a human construct, something that came about through the need of society to regulate human partnerships

Julia Cole

Researcher Dr Michael Lyons said: "That surprises me. So many traits - even very complex social ones - have a detectable genetic influence."

Dr Lyons believes that environmental factors swamp any genetic influence on marriage because people are generally young when they wed, and their decision rests heavily on the success or failure of their parents' marriage.

But once in a marriage, other factors kick in.

He thinks the genetic influence on divorce is related to factors such as drug abuse, depression and alcoholism, which have a genetic component.

The team found that twins who were pathological gamblers, for instance, were 2.8 times more likely to get divorced than the norm for the day.

Dr Lyons said: "Almost any kind of psychopathology is going to make staying married harder."

Counsellor's view

Julia Coles, a psycho-sexual therapist and counsellor for the marriage guidance charity Relate, told BBC News Online: "We know through counselling that people who are able to express their thoughts and emotions in a way that is not threatening to their partner are more likely to have long-lived marriages.

"It may be that this ability is down to a genetic predisposition."

She said genetic instinct might well explain the need for people to form partnerships, but not necessarily the decision to get married.

"The desire to love and be loved, and to want security is likely to have a very ancient origin.

"But marriage is a human construct, something that came about through the need of society to regulate human partnerships."