After assessing nearly 1000 pairs of adult twins, researchers at the University of Edinburgh found that strong genetic influences have a major influence on how loyal a person feels to their social group.

It also has a significant impact on how flexibly they can adapt group membership.

Family ties were less influential. Instead factors outside the family such as ethnicity and religion seem to account for the environmental influences that determine how successfully a group will operate.

To assess the influence of genetics, scientists asked the twins a series of questions about how important it was for them that people with whom they are affiliated share their religion, ethnicity or race.

They found that identical twins -- who share all their genes -- gave very similar responses, whereas non-identical twins were much more likely to differ in their answers.

Interestingly, they found that being part of a strong religious group made subjects less likely to emphasize ethnic and racial influence when deciding with which coalitions they become involved, regardless of genetics.

Professor Timothy Bates, of the University of Edinburgh's School of Philosophy, Psychology and Language Sciences, who led the research, said: "The success of a coalition reflects the genetic make-up of the group members as well as cultural factors such as and shared goals, beliefs, and traditions."

This research could be applied to investigate affiliation in areas such as work, sport and the military."

The study, which is the first to examine the impact of both genetics and environment on how people form groups, is published in Psychological Science journal.

Note: If no author is given, the source is cited instead.

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