I mean, why would we want
to form relationships with people who disagree with everything we
say or do?
To share interests and activities with another person - to eat certain foods, play certain sports, listen to certain music, and so on - is a beautiful, communal, and enriching thing.
But have you ever
considered the science behind why we choose our friends?
For their findings (Friendship and Natural Selection) which were published in the Journal of the National Academy of Sciences (PNAS), the team of researchers analyzed the genomes of 1,932 people, and compared pairs of friends with pairs of strangers.
The study discovered that, on average, every person had more similar DNA with their friends than with strangers. The researchers suggested that such an outcome points to our tendency to make friends who share similar racial backgrounds.
The study concluded that, on overage, our friends can be compared to our fourth cousins genetically, which means that we share an estimated 1% of our genes with our friends.
And as Christakis explained,
Christakis and Fowler also created a "friendship score" in order to predict who will befriend whom at nearly the same level of confidence scientists have for predicting a person's chance of obesity or schizophrenia on the basis of genes.
The team found that, in relation to individual genes, friends are more likely to have similar genes related to the sense of smell, but different genes that control immunity.
This led them to conclude that friends are relatively more dissimilar in their genetic protection against various diseases. Such an evolutionary mechanism - having connections to people who are capable of withstanding different pathogens - can serve society in general, since it reduces interpersonal spread of disease.
But it is still unclear how we select people to gain this immunological benefit.
The study discovered that genes that were more similar between friends seem to be evolving faster than other genes. According to Christakis, such findings may reveal why human evolution seems to have accelerated over the past 30,000 years.
Christakis also noted that,