Sydney, May 29 (IANS) There is a limit to the maximum number of people you can choose to connect with in a social network, and that limit has largely remained unchanged since humans lived in hunter-gatherer societies over thousands of years ago, finds a new study.

"When you have got this network of relationships, there are a lot of things going on in that network. It takes a lot of brain power to actually socially navigate these large networks and there's an upper limit to our ability to do that," said study lead author Michael Harre from the University of Sydney.

Harre and colleague Mikhail Prokopenko have now calculated how that limit -- known as Dunbar's Number -- is reached.

"For humans the limit is around 132 individuals," Harre said.

The limit applies to small groups in both hunter-gatherer societies and modern societies where people are increasingly getting connected to one another using online social networking sites like Facebook, Linkedin and Twitter.

The study, published recently in the Royal Society journal Interface, however points out that you don't have to maintain relationships with everyone in the group for it to remain cohesive.

"To connect together a group of 132 individuals we estimate the average number of links each individual has to be able to maintain is between four and five," the researchers said.

According to the study, a person in a group of five such as a book club or group of friends needs to maintain an average of one to two links. A person in a group of 15 needs an average of two to three links, and a person in a group of 45 needs an average of three to four links.

"The strength of our result is in showing that it is sufficient to add just one connection per person on average while increasing the size of the group roughly three-fold," Prokopenko said.

It means you don't have to like or even be friends with people to co-operate with them -- as long as others in the group do.

"You only have to like enough people to bind the group together," he added.

This would have been important in the days when hunter-gatherers needed, say, 15 people to cooperate in the hunting of a mammoth.

"All you need to do is like two or three people in that group and that's adequate for you to go off and hunt with them," Prokopenko said.