In a recent report researchers at Harvard and the University of California, San Diego said whether a person is sociable or shy is an inherited composition and in our genes.

The study was conducted by Nicholas Christakis of Harvard, as well as Christopher Dawes and James Fowler of UC San Diego. They studied 1,110 twins some identical and the rest fraternal in a population of more than 90,000 adults. They measured indications of popularity such as the number of times an individual was named as a friend, as well as indicators like if a person tended to be at the centre or edge of a social group.

The researchers found greater similarities between the social networks of identical twins than of fraternal twins. This finding was important as identical twins come from the same egg and carry the exact same genes while in fraternal twins the genes vary slightly as they are fertilized separately.

Fowler called the finding revolutionary and said, "There has been a simple model for the metabolic, neural and Internet networks, and the same model is applied to human beings -- that all parts of the network are identical and interchangeable." This he said could no longer be said about human social network interactions. "There are inherent characteristics that govern where we [as individuals] gravitate to in the social network."

Fowler said, "One of the things that the study tells us is that social networks are likely to be a fundamental part of our genetic heritage. It may be that natural selection is acting on not just things like whether or not we can resist the common cold, but also who it is that we are going to come into contact with."

The report was in Tuesday's edition of Proceedings of the National Academy of Sciences.

Fowler and Christakis who have done several studies on social networking, said there may be an evolutionary explanation for this genetic influence and the reason for some people to be at the centre while others are at the edges of the group.

"A second implication is that the study suggests that if we really want to understand how things diffuse in social networks, we need to take into account people's locations in the social networks, which are due in part to their genes," Christakis said.

The researchers reported one finding that was surprising being that an individual's genetic makeup can influence the behavior of other's. "My genes can influence the probability that two of my friends will become friends of each other," Fowler said. The researchers said the finding may not help us change the way we are genetically but this "can help us make sharper predictions about which experiences you have will have the sharpest impact on what social interactions you have."