We are genetically more similar to our friends than to strangers, according to a controversial, new study by US researchers.

Comparing the differences between 2,000 people recruited as part of a study in a small town in the USA, researchers found that friends shared about 0.1% more DNA among themselves as they did with strangers.

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Although the study involved a small group, the result shows the same level of similarity that can be found among fourth cousins.

The study released by the Proceedings of the National Academy of Sciences sparked some skepticism among scientists.

James Fowler, one of the study's authors and a professor of medical genetics and political science at the University of California, said these were unusual findings that caused many scientists to be critical of the study. 

Along with Nicholas Christakis from Yale University, Fowler analyzed around 500,000 single-letter markers across the genome with data compiled from the Framingham Heart Study.

Participants in their survey were asked to provide DNA samples and information about who are their closest friends in the community.

Fowler said these participants are also friends with other participants since the town is relatively small, which apparently contributed to the study's results.

Using a "kinship coefficient," a formula derived from genetic markers from pairs of friends and strangers, Christakis discovered that the results were slightly higher among friends.

Fowler still says it's not clear why friends have more similar DNA than strangers. It's a possibilty that people who have similar genes are exposed to similar ennvironments, which gives them a chance to interact with each other. 

Fowler believes our sense of smell also subconsciously helps us choose our friends. It's been noted that our sense of smell genetically judges and predetermines who we want to interact with.

On a more important note, people who share certain genes also share certan skill sets that are more valuable when it comes to working together.

Fowler said these findings could also apply to groups outside the Framingham study group, whose participants were mostly Irish and Italian.

Thie study by Fowler and Christakis could also explain how behaviors such as altruism develop and evolve through time where DNA similarities among friends can play a crucial role in studying human behavior. 

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