I’m pretty sure that all of you already heard observations like these : ” Their entire family is so calm”, or “this behavior runs in their blood”. We all know people around us that have similar characteristics to their parents and so on. Indeed, there are loads of scientific papers showing that some behavioral traits have genetic basis.
Today I want to share a behavioral genetics study that goes beyond familial genetics and deals with friendship.
Paper Title : Friendship and natural selection
What it really means : You and your friend have a genetic connection too.
Talking about friendship, it is quite obvious to assume that we have more chances to establish a bond with similar people (similar interests). Of course, we also know that some people are attracted by opposites.
However, I hope you agree that the chances of striking up friendships with similar people are higher. This is could be due to the fact that :
- We tend to meet people who are close ( the same city, the same country, the same geographic place).
- We choose friends based on a certain personality or behavior that we like.
- We also sometimes pick up friends who are in a specific/particular environment. For instance I have more chances of meeting an outgoing person (like me) at a bar.
- In situations were I’m forced into a certain environment for professional reasons ( for example), I still have high chances of meeting with similar people. Imagine your boss sending you for a conference about your project, where you WILL end up meeting people interested in it.
Now you could also imagine that it is way more complicated and all of these events could happen at the same time, making the selection process of friends quite difficult to trace back and understand easily.
However in this study, both authors, wanted to try and see if there was any genetic connection that could explain this selection process.
To answer this question, a large DNA analysis was done on 1,932 people, of which 1367 had a connection with at least one other person from the study.
What was analyzed?
466,608 different single nucleotide polymorphisms ( SNPs), which are small changes in the DNA sequence that differentiate us from one another.
To make a long story short : We have more DNA in common with the people we select to be our friends compared to the strangers around us. About 1% of our genes are shared with our friends.
Intriguingly there was more:
- The genes that were the most alike between friends were genes involved in the olfactory system. Basically friends smell things the same way.
- The genes that were the most different between friends were involved in the immune system. Basically friends have a different/complementary immune system compared to ours.
To conclude on a personal note, I personally tend to pick up friends who like good food and drinks, I wonder if it’s due to the smell… Concerning the immune system, there is solid data suggesting that we tend to pick up mates that offer us extra or complementary immunological protection.
This study has added to a list of interesting studies in behavioral genetics in recent years.
We hope to bring you up to date with more such studies on this forum!
- Christakis NA1, Fowler JH2. Friendship and natural selection. Proc Natl Acad Sci U S A. 2014 Jul 22;111 Suppl 3:10796-801. PMID: 25024208.