The microorganisms in our bodies make people come closer and help each other, even when they are not genetically related
According to the principles of natural selection, only behaviors that help the individual to survive and reproduce continue to exist. However, many phenomena exist even when it is not clear what benefit they give to the individual performing them or to his genes. Prof. Lilach Hadani from the School of Plant Sciences and Food Security at Tel Aviv University, and her team, which includes doctoral students Yael Gurevich and Ohad Levin-Epstein, are trying to decipher these phenomena with mathematical tools and understand what enables and motivates them. Thus, for example, they study the evolution of cooperation and altruism.
What is the interest of an individual to help another at his own expense. After all, according to Darwin, the father of the theory of evolution, in order to produce offspring and survive, the individual must fight for limited resources in nature. Therefore, why should he be generous to another? Or will he even sacrifice himself for it? According to Prof. Hadani, "Cooperation in nature is a common phenomenon, and it does not always stem from understandable reasons such as blood ties and reciprocity. In many cases it exists between individuals who are not genetically related, and even between completely different species. We asked ourselves how the genes that contribute to cooperation and altruism spread in the population, and proposed the possibility that the microbiome - the trillions of microorganisms (such as bacteria) that live in our bodies, and especially in the gut - has a role in this. It is possible that the genes of the microbiome contribute to social behavior. Because, today it is already known that the microbiome can also affect the host's behavior and not only his health."
Since 2007, when researchers announced the Human Microbiome Research Project, more and more research evidence is being revealed about the decisive influence of the microorganisms in our bodies on our physical and mental health. Some can cause serious infectious diseases, such as inflammatory bowel disease, and some can fight them. Some also produce neurochemicals that may affect behavior, which pass from the gut to the brain (a pathway called the "gut-brain axis").
Interaction and physical proximity are known to allow these and other microorganisms to pass from individual to individual. In addition, it is known, as mentioned, that they produce neurochemicals in the host's body, including neurotransmitters such as serotonin and dopamine, which reach the brain and may lead to a desire for contact, help, closeness, and the like. Thus, according to Prof. Hadani, because natural selection works in favor of the genes of the microorganisms that manage to spread and survive, they encourage the host to create positive interactions (such as feeding and protection) with another individual. And so the microorganisms may both infect the other individual and help the survival of their relatives who will pass to him through interaction. That is, they manipulate their host so that they can spread their genes, and possibly make it social and cooperative.
Paternal care is a unique example of altruistic behavior. In one of their latest studies, Prof. Hadani and her team examined the role of the microbiome in the development of this treatment. They built a probabilistic-mathematical-evolutionary model that was based on two family structures: female, male and their offspring versus female, male and mixed offspring (even those that may belong to another male). Using the model, they tested whether genes of the microbiome can encourage fathers to take care of their offspring (by secreting the appropriate neurochemicals in their bodies), even when the chance that these offspring are theirs is not high. If only the genes of the fathers are taken into account, many times they are expected to invest energy in finding additional partners, in spreading their sperm and producing as many offspring as possible, rather than in paternal care. Therefore, the question arises, when will they still prefer to take care of offspring instead of looking for additional marital opportunities?
The model showed that the microbiome bacteria of the ancestors may contribute to this; When a father interacts with the offspring (e.g. feeding) he may also transfer bacteria to him. That is, the interaction increases the transfer of microbial genes, and of course it does not require genetic kinship between the father and the offspring. In addition, taking care of the offspring increases its chances of survival - and that of its microbiome. In such a situation, bacteria that encourage paternal care will have an advantage. Therefore, the microbiome may explain paternal behavior even among fathers who apparently have no interest in it (eg when their offspring are adopted). Although this study requires empirical testing, in the meantime it can be concluded that the microbiome may play a significant role in paternal care. Another conclusion is that factors that dramatically affect the composition of the microbiome (such as antibiotics) may change the relationship of a father to his offspring.
Life itself:
Prof. Lilach Hadani, 47 years old, married and mother of two children (ages 9 and 12). In her spare time she likes to read, travel and practice yoga. She chose to study evolution because "I'm more interested in the 'why' than the 'how'".
