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Friends: Sharing to the genes

Humans are probably the only species where virtually all individuals form stable bonds and not related to reproduction. That is, virtually all have friends. Some studies suggest that friends share physical or behavioral characteristics, in other words, we have seen that there may be phenotypic similarity friends. What is not clear whether this similarity reflects a similar phenotypic genotypic , that is, do we share genes with our friends? Image Xzit taken from Wikimedia Commons . From the biological standpoint, this question is interesting for several reasons. One is that genetic similarities exist between friends that would increase the possibility that natural selection operate level group. It is also important when we consider the indirect genetic effects. In other words, the phenotypic characteristics of an individual could be affected by the genes of those individuals close to the genes of the guys then. Several human studies have shown that there is a tendency to associate with those with whom we resemble ("God makes them flock together"), a process known as homophily . One can argue that social influence is undeniable that involve individuals who are alike, but it is also true that the phenotypic similarities may have a strong genetic component whether you believe in physical characteristics or behaviors. But how we ended up near those with whom we also share genes? The thing is perhaps more simple than it seems. Let's see why. First, groups with little mobility where reproduction occurs among those who are closer, it is almost inevitable that ultimately the individuals within a group share a number of genes. This phenomenon is known as population stratification. Second, individuals can "actively" seek out those with genotypes similar to ours, and not because we are able to recognize their genes but because we are able to recognize the phenotype, which is the expression of the genotype. Third, individuals can choose those environments-either actively or passively, in which the expression of our genotype is optimal, it is therefore natural that when we find ourselves with individuals who have also chosen the same environment in terms of genotype. For example, those prone to vigorous physical activity may be more likely to join a gym where people end up joining with other equally active. Image Spazzykoneko taken from Wikimedia Commons . is important to note, however, it is also possible to observe heterophyly . That is, people can actively choose those individuals who do not share characteristics (where opposites attract). This process appears to be relatively common during mate choice or may occur under certain circumstances. For example, in the workplace people with different skills and (potentially) different genes can be found within the same space. On 1 February in the Journal of Proceedings of the National Academy of Sciences , published an article - in which this input is based on the genotypes found within networks of friends. For the study, led by James H Fowler the University of California at San Diego, the authors used a database called Add Health ( National Longitudinal Study of Adolescent Health ). As part of the data collected for this database took saliva samples to identify the presence of 6 genes. Hence, the authors extracted information from pairs of friends (not related) as well as information on gender, age and ethnicity of them. One of the objectives of this database is just to have information about the behavior and adolescent health. According to their results, there is some genotypic group in social networks that can not be explained solely by population stratification. That is, friends do not just resemble each other, if not also occur at these genotypic similarities. Although the genes considered were associated with certain personality characteristics and behavioral phenotypes is well known that with which these genes are most likely associated polygenic (ie, are affected by many genes) and pleiotropic (affects various features), which in some way guarantee the strength of its conclusions. The authors found that for example there was some grouping of genotypes (homophily) in the DRD2 gene has been associated with alcoholism, which makes sense if we think that those more inclined to drink would feel better with other individuals with this tendency. On the other hand, the lack of connection between individuals with the CYP2A6 gene (associated with the opening social) suggests some heterophyly for that gene, even if not completely clear because those individuals actively seek social open to those who are not. Still, the authors suggest that the fact that there are some genes for which there is heterophyly is proof that individuals actively select their friends. One of the interesting conclusions can be drawn from this study is the fact that the genetic structure of human populations is not only a result of reproductive unions. Friendly ties can also have an important impact on the structure. addition, homophily and heterophyly present among individuals within a group may have interesting implications in the way in which genes lead us to certain environments and social influence that the environment can have on our behavior. That is, humans can actively search for friends with certain genotypes, which in turn facilitate the expression of certain genes. This could therefore affect the development of other phenomena such as spread of diseases, information, etc. James H. Fowler, James E. And Nicholas A. Settle Christakis, authors of the study suggest that maybe we could see the genetic landscape of an individual as the sum of the individual genes in question and the rest of the guys around him, just as in other organisms such as bacteria and laying hens. Evolutionarily speaking social environment could be an important selective force than perhaps we thought. Within a network there may be genetic niches that promote or inhibit the development of certain types of behaviors such as those related to the acquisition of certain diseases, cooperation among individuals, etc. The authors speculate further, suggesting that the genetic characteristics of certain groups may confer adaptive advantages. However, this is as yet experimental question (which has to be tested) and will be interesting to discover and understand under what conditions, besides the presence of certain genes, such adaptive advantages may be observed in individuals as mobile like humans. Reference article:

Fowler, J., Settle, J., & Christakis, N. (2011). Correlated genotyped in friendship networks Proceedings of the National Academy of Sciences, 108 (5), 1993-1997 DOI: 10.1073/pnas.1011687108