I love you. Actually, I love your microbiome
Blog Author: Bill Miller, MDPosted: Friday, February 6, 2015 - 16:58
What determines chemistry between two people? Who has not said, “They have good chemistry together?” What if the concept of chemical attraction has a direct biological basis?
New research is revealing that it does. It is becoming increasingly apparent that our microbiome has a tremendous influence upon us. The microbiome represents all the microorganisms that are in us and on us. That combination of microbial and innate genetic code is now referred to as the hologenome. It has been found that the microbial cells that are in us and on us outnumber our innate cells by a factor of ten to one. Their influence is a crucial element of metabolic pathways, including glucose regulation, and they are essential in mediating our immune systems. They even partially regulate our emotional responses to stress.
Our relationship with these obligatory microbial partners is intimate. We cannot survive without them. It should not be totally surprising then that they can affect our social choices. Yet, those factors had remained hidden from our appraisal until recently since we had lacked the technological means to assess them. Current research has found that the amount of microbial life in our mouths is startling and the transfer between kissing partners is extensive. However, the particular surprise is that although frequent intimate kissing between partners does correspond to the composition of the microbes that are shared between each, there is a shared linkage in microbial composition between the mouths of sexual partners that operates regardless of kissing frequency. The implication is that there is a background connection with the microbial realm that might influence our initial choices of sexual partners and that also extends beyond shared environmental factors. For example, the microbiota on the back of the tongue is more similar between kissing partners than unrelated individuals, but that identity does not clearly correlate to any kissing behavior or frequency.
Could it mean that we are attracted to one another on the basis of forces that are unapparent to our typical senses? There is other evidence to suggest that this is the case. Experiments have shown that we are unconsciously attracted to other partners whose immunological histocompatibility is complementary to our own. This makes sense from an evolutionary perspective. The combination of immunological capacities of healthy mates that differ confers better protection to the next generation. Experiments have demonstrated that sexual partners are attracted to certain body odors. For human odors, microbes matter. However, in a crucial evolutionary twist, that odor attraction is not for similarity but for opposite types. In the aggregate as a species, we seem to search for other sexual partners that are not our precise immunological match. When contrasting individuals both mix genes and share microbes, the next generation gets a boost.
What should we make of all this? The next time you gaze lovingly at your favorite other, tip your hat mentally to your hidden microbial partners. In truth, your microbiome might have made you do it.
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4. Chaix R, Chen C, Donnely P. Is mate choice in humans MHC-dependent? PLoS Genet 2008;4:e1000184.
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This posting has not been peer reviewed by the BCMJ Editorial Board.