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Genotype Similarities Between Friends - Coggle Diagram
Genotype Similarities Between Friends
Background
It is known that some friends tend to have similar phenotypes (homophily), while others tend to befriend people with opposite phenotypes (heterophily) (Christakis and Fowler, 2014).
Potential Reasons for Heterophily:
-An individual may be in an environment that fosters interaction between people who are different from each other.
-Some people may actively choose to only foster friendships with people who are different from them (Christakis and Fowler, 2014).
Potential Reasons for Homophily (not mutually exclusive):
-Byproduct of befriending people who live in the same area as you, therefore you share some ancestry.
-Some people actively choose to foster friendships only with those who are similar to them.
-Some choose to be in environments that inherently contain people with similar phenotypes.
-Maybe the result of a third party putting someone into a situation where they come in contact with similar people (Christakis and Fowler, 2014).
Hypotheses
If there is a selective advantage to homophily, you would gain fitness in more interactions than you would if there was a heterophilic selective advantage (Christakis and Fowler, 2014).
There are more genetic similarities between friends than there are between strangers (Christakis and Fowler, 2014).
There is a positive selective pressure for gene similarity between friends (Christakis and Fowler, 2014).
Results
Difference in means test shows that friends tend to be more genetically similar than strangers. Friends have the same relatedness as 4th cousins (Christakis and Fowler, 2014).
Friends exhibit a significantly larger amount of both homophily and heterophily than strangers do (Christakis and Fowler, 2014).
Certain genes between friends show overwhelming levels of similarity (Christakis and Fowler, 2014):
-Olfactory senses
-Linoleic acid metabolism
Friends tend to have opposite genotypes with respect to coping with infections (Christakis and Fowler, 2014).
Homophilic genotypes are increasing in frequency due to positive selection pressure (Christakis and Fowler, 2014).
Conclusion
The results from these experiments support the evidence that humans may be metagenomic with other humans in their vicinity, so they seek out social environments that increase their fitness (Christakis and Fowler, 2014).
Friends who are genetically similar to you can be considered as functional kin. In this respect, the olfactory and linoleic acid metabolism genes may be a tool used in kin recognition (Christakis and Fowler, 2014).
Having friends who are resistant to pathogens different from you increases group fitness, since it prevents the spread of multiple pathogens within the group (Christakis and Fowler, 2014).
References
Christakis NA, Fowler JH. 2014. Friendship and natural selection. PNAS. 111(3):10796-10801.